title: A Goofy Movie

text: Since its release, "A Goofy Movie" has underwent critical reevaluation and is now appreciated as a "true cult classic". In a 2020 editorial for Rotten Tomatoes, Rafael Matomayor wrote: "Featuring a small-scale story that kids can see themselves in, an excellent portrayal of teenage life and father-son relationships, and, crucially, a soundtrack filled with earworms to rival the work of Rice and Menken, the movie has something for everyone." Nell Minow of Common Sense Media praised the low-key tone and humor of the film, concluding: "Even tweens will enjoy this road trip with Goofy." The Mary Sue’s Princess Weekes cited the soundtrack and story as to why the film "remains a perfect father/son film".


title: A Goofy Movie

text: The film was nominated for "Best Animated Feature" in the production categories and "Best Production Design", "Best Storyboarding", "Best Music", and "Best Animation" in the individual categories at the 23rd Annie Awards.


title: A Goofy Movie

text: After its underwhelming box office performance during its theatrical release, "A Goofy Movie" started to gain success in 1995 to home media sales, and soon gained a cult following. The interest in the film is attributed to a combination of the film's catchy soundtrack as well as its story of cross-generational connections between parents and children. The newfound interest led to waves of new merchandise based on the film to be sold at major retailers.


title: A Goofy Movie

text: On August 14, 2015, a 20th-anniversary reunion for the film was held at the D23 Expo at Anaheim Convention Center in Anaheim, California. Those in attendance included Bill Farmer, Jason Marsden, Jim Cummings, Rob Paulsen, Jenna von Oÿ and producer Don Hahn. Wallace Shawn, Pauly Shore and director Kevin Lima also sent video messages. The panel also included musical performances from Farmer, Marsden, and Tevin Campbell. While the panel was not expected to be one of the largest panels at D23, it ended up with the largest attended, with around 1,000 fans attending, and forcing the expo to turn away some due to lack of seating.


title: A Goofy Movie

text: In the video game "Disney Magic Kingdoms", Pete, who appears as character, makes some references to the film, wearing the same clothes and owning the same recreational vehicle with which he goes camping.


title: A Goofy Movie

text: In 2016, Campbell uploaded a video of him partaking in a jam session with the band Enfield, in which he performed both "I 2 I" and "Stand Out". In June 2018, a one-week event titled "Disney FanDaze" was opened in Disneyland Paris, featuring several dedicated performances paying tribute to Disney franchises. Among these was "Max Live! Gettin' Goofy With It", which featured Max Goof performing songs from "A Goofy Movie". In April 2019, singer Uché performed "I 2 I" during the Top 10 Disney Night of "American Idol"s seventeenth season. According to co-producer Frank Angones, the film was a strong influence during early development of the 2017 "DuckTales" series, particularly on its version of Donald Duck, as the creators "wanted [the] show to do for Donald what "Goofy Movie" did for Goofy". The series itself featured several references to the film, including the appearances of the song "Stand Out", Lester's Possum Park, and pictures of Goofy, Max, and Roxanne. In October 2021, Cody Rigsby and Cheryl Burke danced a Jive to "Stand Out" during night one of Disney Week on the 30th season of "Dancing with the Stars". During an interview with i-D for Paul Thomas Anderson's film "Licorice Pizza", lead actress Alana Haim called "A Goofy Movie" her favorite movie of all time, stating “If you haven't seen it, you need to watch "A Goofy Movie". It's the best movie of all time.”


title: A Goofy Movie

text: The visual design of a scene in "A Goofy Movie" where Goofy and Pete have a conversation in a hot tub was cited as an inspiration for a similar scene in the season 2 episode of "Gravity Falls" "Roadside Attraction" in the episode's DVD commentary.


title: A Goofy Movie

text: In 2022, Pixar director Domee Shi said she was inspired by "A Goofy Movie" for the story of her directorial debut, "Turning Red" (2022).


title: A Goofy Movie

text: The eighth episode of "Atlanta"’s fourth season, titled "The Goof Who Sat By the Door" , was a mockumentary about the making of the film.


title: A Goofy Movie

text: A direct-to-video sequel to "A Goofy Movie", titled "An Extremely Goofy Movie", was released on DVD and VHS in 2000 and serves as the finale to the "Goof Troop" series as a whole. Characters that returned for the sequel were Goofy, Max, P.J., Pete, and Bobby, but Roxanne is absent from the sequel and is not referenced. In it, Goofy loses his job and enrolls in the college which Max recently started attending, while Max and his friends participate in the X Games, unaware of the reason why the school's top fraternity has a dynasty in the competition.


title: Terraria

text: Terraria is an action-adventure sandbox game developed by Re-Logic. The game was first released for Windows on May 16, 2011, and has since been ported to several other platforms. The game features exploration, crafting, building, painting, and combat with a variety of creatures in a procedurally generated 2D world. "Terraria" received generally positive reviews and sold over 44 million copies by 2022, making it one of the best-selling video games.


title: Terraria

text: "Terraria" is a 2D sandbox game with gameplay that revolves around exploration, building, crafting, combat, survival, and mining, playable in both single-player and multiplayer modes. The game has a 2D sprite tile-based graphical style reminiscent of the 16-bit sprites found on the Super NES. The game is noted for its classic exploration-adventure style of gameplay, similar to games such as the "Metroid" series and "Minecraft".


title: Terraria

text: The game starts in a procedurally generated world, with players starting out with basic tools and a non-player character (NPC) guide to get them started and bring their attention to aspects of the game and progression. The game's world is made up of several layers of tiles that players can interact with and modify. Many resources, such as metal ores, can be found while exploring caves. Players begin with low health and mana, which can be increased by finding and crafting specific items. Some resources may only be found in specific areas of the map, stored in common and rare containers, or dropped by certain enemies. Players use resources to craft new items and equipment. Different recipes require different resources and crafting stations. Several items in "Terraria" create complex crafting trees involving a large amount of items to create a single powerful piece of equipment.


title: Terraria

text: Players have the option to customize their character's appearance when creating a new character, and in-game by visiting the Stylist NPC or the Clothier NPC. Along with that, players can obtain vanity items, which are special armor pieces and accessories with only a cosmetic effect, and dyes to change the color of equipped armor or accessories. Characters have three inventory slots for armor to be equipped, and several inventory slots for various accessories to provide a boost to a player’s statistics, such as wings or water walking boots, as well as vanity slots for all of them, allowing them to be hidden behind cosmetics while retaining their effects. Much like most Terraria items, armor and accessories can be crafted, found around the world, and obtained from defeating bosses.


title: Terraria

text: Players can encounter many different types of enemies in "Terraria", the occurrence of which depends on several factors including time, location, and random events. The game features an open-ended class system, primarily divided into melee, ranged, magic and summoner classes. Players may also battle bosses that utilize a number of different combat mechanics and can drop rare and valuable items. Bosses are summoned by using certain items or when certain criteria are met. The defeat of some bosses is directly tied to in-game progression, while others remain optional. Defeating the Wall of Flesh boss advances the game into "hardmode", which adds many new enemies throughout the world, as well as new NPCs and items. Like bosses, players can battle special enemies and mini bosses during invasions, in which enemies appear constantly and they either must be defeated or a certain amount of time must pass before the event ends. "Terraria" also features seasonal events which activate during certain periods of the real world calendar year, adding new enemies and content.


title: Terraria

text: By completing specific goals, such as defeating a boss or obtaining a certain item, players can attract NPCs to occupy structures or rooms they have built, such as a merchant, nurse, or wizard. Some NPCs can be acquired by finding them throughout the world and will then reside in player-created houses after being rescued. Players may then buy or sell items and certain services from NPCs with coins obtained from defeating enemies and bosses. The game features many different biomes and areas, which are each home to a unique set of enemies and challenges. The Corruption, Crimson, and the hardmode-exclusive Hallow, will expand by slowly overtaking and converting nearby blocks. NPCs prefer to be around certain biomes and with certain other NPCs, and will raise and lower their prices and sell special items depending on if they are sufficiently happy.


title: Terraria

text: "Expert" and "Master mode" are difficulty modes that increase the challenge of the game in exchange for some exclusive items. "Journey" mode allows players to duplicate items, adjust the world's difficulty, and control weather and time at will while playing.


title: Terraria

text: "Terraria" has support for mods, which is facilitated by the third-party tModLoader. It later received official support when it was released as free downloadable content alongside the "Journey's End" update on Steam in 2020.


title: Terraria

text: Development of "Terraria" began in January 2011 by Re-Logic, built on the Microsoft XNA framework and written in C Sharp. Re-Logic was composed of Andrew Spinks, who designed and programmed the game; Finn Brice, who, along with Spinks, did the graphic design for the game. The music was composed by Scott Lloyd Shelly. The game was released for Windows on May 16, 2011. In December 2011, the game was updated to version 1.1, adding new monsters, bosses, NPCs, and items. The update also included improvements to the game's world generation technology and lighting system. In February 2012, the developers announced that they would not continue development but would release a final bug-fix patch. However, development resumed in 2013 with Spinks asking the community for ideas to include in future content updates.


title: Terraria

text: In September 2012, Spinks announced that Engine Software and 505 Games would be porting "Terraria" to Xbox 360 and PlayStation 3. The game was released for Xbox 360 via Xbox Live Arcade on March 27, 2013. The PlayStation 3 version was released via the PlayStation Network in North America on March 26, 2013 and in Europe and Australia on May 15, 2013. Shortly after the initial console release, 505 Games announced "Terraria" for PlayStation Vita; it was released in Europe on December 11, 2013, and in North America on December 17, 2013. Spike Chunsoft localized the PlayStation 3 and Vita versions for release in Japan, including exclusive items such as a costume based on Monokuma from their "Danganronpa" series. In May 2013, 505 Games announced a mobile version of "Terraria" ported by Dutch studio Codeglue for Android, iOS, and Windows Phone. It was released for iOS on August 29, 2013, and for Android on September 13, 2013. The Windows Phone version was released on September 12, 2014.


title: Terraria

text: In October 2013, Re-Logic released version 1.2 for "Terraria" on Windows. The update added a host of new mechanics, gameplay changes, and graphics adjustments. After the 1.2 update was released the game returned to receiving continuous updates. The console and mobile versions received the update in 2014. "Terraria" released on GOG.com on October 2, 2014. A downloadable version of "Terraria" was released for PlayStation 4 on November 11, 2014, and Xbox One on November 14, 2014, with a retail release on December 2, 2014. In September 2014, Re-Logic announced that "Terraria" would be coming to macOS and Linux. They were both released on August 12, 2015. The Nintendo 3DS version was first released on the Nintendo eShop on December 10, 2015. A Wii U version was released on the eShop in June 2016.


title: Terraria

text: Version 1.3 was released on June 30, 2015, adding even more items, events, enemies, bosses, and gameplay features. The update was released for consoles on December 12, 2017, and was released for mobile on August 27, 2019. In July 2016, 505 Games announced that Engine Software and Codeglue would no longer be working on the console and mobile versions respectively and that a new studio, Pipeworks, would take over the development of those versions. A version for the Nintendo Switch, ported by 505 Games, was released on June 27, 2019. In December 2018, 505 Games announced that development of the 1.3 update for mobile would be taken over by DR Studios to help Pipeworks focus on the Switch port of the game. In August 2020, Re-Logic announced that development of the Console and Switch would be taken over by DR Studios.


title: Terraria

text: The fourth and final major update for the game, "Journey's End", was released on May 16, 2020, the ninth anniversary of the game's initial release. As with previous updates, it added new items, enemies, difficulty modes, and gameplay features.


title: Terraria

text: In February 2021, Spinks announced the cancellation of the Stadia port of "Terraria" due to the suspension of the Re-Logic/Spinks's Google account without a given reason for over three weeks. He also announced that Re-Logic would not be working with Google again in the future stating, "I will not be involved with a corporation that values their customers and partners so little. Doing business with Google is a liability." He later clarified that existing Android and Google Play versions of the game will not be affected. Later that February, Google reached out to Re-Logic about the account shutdown and provided transparency around the situation and restored their accounts, and subsequently, Re-Logic reaffirmed that they still planned to release the game for Stadia, which it did on March 18, 2021.


title: Terraria

text: A March 2021 update for the Steam version of the game added direct support for resource packs, worlds, and character sharing through the Steam Workshop. tModLoader is still used to help provide and install user-created mods for the game. In November 2021, a crossover update added content from the survival game "Don't Starve Together", which received its own "Terraria"-themed content in return. An update known as "Labor of Love" was released on September 28, 2022.


title: Terraria

text: In October 2013, Spinks announced that he was planning "Terraria 2", stating that it would be significantly different from the original game. "Terraria: Otherworld", announced in February 2015, was another game that was set be released later that year. "Otherworld" tasked the player with trying to purify the world of the Corruption, which was to be achieved mainly by finding and activating "purifying towers" that push back the spread of the Corruption. "Otherworld" would have included more strategy and role-playing elements, such as a tower defense gameplay element, skill trees, and a plot. In April 2017, Re-Logic announced that the previous partner on the project, Engine Software, would be dropped in favor of a new studio, Pipeworks, due to the game being behind schedule. A year later, Re-Logic announced that "Otherworld" had been cancelled due to them not being satisfied with its development.


title: Terraria

text: "Terraria" received generally favorable reviews from critics, according to review aggregator Metacritic. A review for "Destructoid" included praise for "Terraria" as "full of depth". Another reviewer praised "Terraria" integration of some of "Minecraft" concepts into two dimensions. "GameSpot" praised "Terraria" exploration and feeling of accomplishment but criticized its lack of tutorial or explicit directions. IGN praised the game, claiming that "Terraria": "expands on the familiar sandbox gameplay with a greater emphasis on combat and adventure." "Terraria" received the #1 of 2011 Indie of the Year Player Choice on IndieDB. "Terraria" has been described as a "Minecraft" clone by various video gaming media outlets.


title: Terraria

text: "Terraria" sold 200,000 copies in just over a week after its release, and over 432,000 within a month. By May 2022, over 44.5 million copies of "Terraria" had been sold, making it one of the best-selling video games of all time. The total is split between 23 million on PC, 12.4 million on mobile, and 9.1 million on console.


title: After Earth

text: After Earth is a 2013 American post-apocalyptic science fiction survival adventure action film directed by M. Night Shyamalan, who co-wrote it with Gary Whitta. The film was loosely based on an original story idea by Will Smith about a father-and-son trip in the wilderness before it was eventually reworked into a sci-fi setting, taking place 1,000 years in the future where humans evacuated Earth to another planet due to a massive environmental catastrophe. It is the second film after "The Pursuit of Happyness" that stars real-life father and son Will and Jaden Smith; Will Smith also produced via his company Overbrook Entertainment, and the distribution was by Columbia Pictures. The film was co-produced by John Rusk, who was also the first assistant director on this film as well as on many of Shyamalan's other films. The film follows father and son, Cypher and Kitai Raige, who find themselves crash-landing on the abandoned Earth. When Cypher gets injured from the crash, Kitai must travel across the wild environment in search of a backup beacon to fire a distress signal, while having to fend himself from the highly evolved animals, as well as an extraterrestrial creature that detects its prey by smelling fear.


title: After Earth

text: The film was released in IMAX on May 31, 2013. Upon release, "After Earth" was panned by film critics, who targeted the story, visuals, performances of Will and Jaden Smith, and Shyamalan's direction. It made $243.8 million at the box office against a budget of $130 million.


title: After Earth

text: In the future on a human-populated space colony, Nova Prime, the S'krell extraterrestrial race attempts to take it over with creatures called Ursas, which hunt by "sensing" fear. Peacekeeping organization The Ranger Corps defeat them with a fear-suppressing technique called "ghosting," but not before an Ursa kills Senshi, the daughter of Rangers' leader Cypher Raige. Kitai, Cypher's son, blames himself for Senshi's death. He trains to become a Ranger like Cypher, but is rejected when he applies. Kitai's mother Faia convinces Cypher to take Kitai on his last voyage before retirement. During flight, however, their spaceship is caught in an asteroid shower, causing them to crash-land on Earth, which the humans evacuated a thousand years ago due to an environmental cataclysm.


title: After Earth

text: The two manage to survive, but Cypher's legs are broken in the process, and the main beacon for firing a distress signal is damaged. Cypher instructs Kitai to locate the tail section of the ship, which broke off on entry to the atmosphere. Inside is the backup beacon, which they can use to signal Nova Prime. Cypher gives Kitai his weapon, a wrist communicator and six capsules of a fluid that enhances oxygen intake so he can breathe in Earth's low-oxygen atmosphere. Cypher warns him to avoid the highly evolved fauna and flora and be careful of violent thermal shifts. Kitai leaves to find the tail section, with Cypher guiding him through the communicator.


title: After Earth

text: Kitai confronts many of the hazards his father warned about, including attacks from baboon-like monkeys, a venomous leech, a thermal shift, and the damaging of two of his capsules. After a story from Cypher about how he conceived "ghosting" to kill the Ursas, Kitai reaches a cliffside waterfall and Cypher learns about the broken capsules. Knowing that the only way to make it with the two capsules would be to skydive, Cypher orders Kitai to abort the mission, but Kitai, believing that Cypher still sees him as a disappointment, goes against the order after a monologue of him blaming Cypher's absence at home for Senshi's death. Kitai is captured by a large condor and his communicator is damaged. In the bird's nest, Kitai tries and fails to defend her chicks against big cats before escaping to a river, where he drifts on a raft. After a sleep where he dreams of Senshi, he wakes up to a thermal shift that nearly freezes him to death. Kitai is rescued when the bird, who had lost her brood when the cats attacked, sacrifices herself for him because Kitai tried to protect her chicks.


title: After Earth

text: Kitai reaches the tail section and tries to activate the emergency beacon, but the atmosphere blocks the signal. Kitai learns that the ship's Ursa escaped and killed the rest of the crew. It attacks him, but Kitai is able to kill it using the "ghost" technique he learned from Cypher. Kitai climbs a volcano to fire the beacon, and he and Cypher get back to Nova Prime via a rescue team.


title: After Earth

text: Will Smith conceived this story when he was watching the television show called "I Shouldn't Be Alive" with his brother-in-law Caleeb Pinkett. It was originally not a science fiction story but about a father and son crashing their car in the mountains or some remote region, with the son having to go out and get rescue for his father. Smith then decided to change the setting to 1000 years in the future, which imposed a higher production budget. The film was also intended to be the first in a trilogy. Smith had his production company Overbrook contact Gary Whitta (who was then known for his script for "The Book of Eli") with a simple log line for a film: a father and son crash landed on Earth 1000 years after it had been abandoned by humankind. Impressed with his idea and excited about the opportunity to work with him, Whitta fleshed out Smith's idea and pitched it to him, subsequently becoming the first employee on the project.


title: After Earth

text: A month after the release of "The Last Airbender", Smith contacted M. Night Shyamalan on August 6, 2010, to wish him a "Happy Birthday" on his 40th birthday and also to persuade him to direct his film along with his son Jaden as the star. Smith and Shyamalan had planned to work on a film before but it never worked out. Impressed with the entire script, Shyamalan officially made this project—then entitled "One Thousand A. E."—his next directorial effort on October 20, 2010, and quietly shelved his own secret untitled project with Bruce Willis, Bradley Cooper, and Gwyneth Paltrow loosely attached. There was another starring role for an adult male, but sources indicated that Smith would not be taking it on. Sony Pictures Entertainment has a first-look deal with Overbrook, so it was expected to be the studio home for "A. E." Shyamalan later suggested the film would feature other members of the Smith family, and that it would not be in 3D but he had "an idea for something kind of technically interesting".


title: After Earth

text: In December 2011, Columbia Pictures, a subsidiary of Sony, signed up both Will and Jaden Smith to co-star in the film with Shyamalan directing. Shyamalan, who also co-wrote the screenplay with Gary Whitta, also additionally co-produced the film with James Lassiter, Ken Stovitz, Will Smith, and Jada Pinkett Smith. Doug Belgrad, president of Columbia Pictures, made the announcement and said, "Night is an outstanding filmmaker who has a tremendous vision for this science-fiction adventure story and we couldn't be more excited to be working again with Jaden after our experiences on "The Pursuit of Happyness" and "The Karate Kid"," and added "We're thrilled to have the two of them together on this project." Shyamalan also added, "The chance to make a scary, science-fiction film starring Jaden and Will is my dream project." Will Smith's decision to take on the starring adult male role required him to step aside in producing and starring in the Hurricane Katrina drama "The American Can", and offered the lead role to Denzel Washington instead. The shooting of the movie was also pushed back from September 2011 to January 2012.


title: After Earth

text: On July 25, 2011, Smith travelled to Costa Rica accompanied by an entourage of about 20 people, including Shyamalan, to scout for locations to shoot the film. They visited sites like the Arenal Volcano, hot springs and a lake, and some beaches.


title: After Earth

text: In September 2012, Columbia committed to a June 7, 2013 release date. Shyamalan also scouted locations in Philadelphia. Fifty percent of the filming was to take place at the new Sun Center Studios in Delaware County (Chester Township). Other locations would be in Costa Rica, Utah and Northern California. Shyamalan also visited Valley Forge Military Academy, the filming location of "Taps", for research of the film, then entitled "After Earth", as Jaden Smith would be playing a military cadet of the future.


title: After Earth

text: The screenplay by Whitta and Shyamalan was later polished by Stephen Gaghan and Mark Boal. Jonathan Young, a psychologist and screenwriter, polished the mythic journey structure. As reported by Screen Rant in 2020, "Some scripts sidelined Will completely in favor of his son, Jaden, but Sony wanted him on the big screen as much as possible."


title: After Earth

text: Principal photography for "After Earth" began in February 2012. Much of the filming took place in Costa Rica, Humboldt County and Aston.


title: After Earth

text: "After Earth" also became the first film from Sony to be both shot and presented in the emerging 4K digital format. It was primarily shot with Sony's CineAlta F65 camera, which was shipped in January 2012. However, a skydiving sequence required a smaller sized Canon Cinema EOS C500 4K camera mounted on the helmet of a professional skydriver. The cinematographer Peter Suschitzky who picked Sony F65 digital camera for the movie over other digital and film cameras, argued that benefits of film are lost when shown in theaters with digital projectors, as many are today.


title: After Earth

text: On April 19, 2013, Shyamalan then announced that the release date had been moved a week earlier to May 31, 2013 in North America and Korea, which put it against "Now You See Me" and "The Purge", scheduled to open in the United States in the same week. A few days later, the U.S. release of "The Purge" was rescheduled for June 7, 2013, taking over the slot vacated by "After Earth".


title: After Earth

text: On May 3, 2013, it was revealed that Korean-American singer Jay Park would be participating on the official soundtrack of the film in Korea, with a song titled "I Like 2 Party". Then on May 5, 2013, another 30-second snippet of the song was then released with another teaser and trailer.


title: After Earth

text: The estimated worldwide marketing budget for "After Earth" was approximately $100 million in addition to the $130 million budget to produce the film. Initial marketing began online with an internet marketing campaign on Facebook and Google+, including a teaser trailer. Alongside the Facebook marketing is a Web 2.0 site that lets people scroll through different images and paragraphs in a complex dynamic way. An image of Jaden's character "Kitai" in costume was released online on February 15, 2012. Later on in the same year, another theatrical teaser was released alongside a trailer for the competing Joseph Kosinski film "Oblivion". On March 12, a modified version of "After Earth"s theatrical teaser was released as the official trailer. The official trailer was broadcast as a TV Spot during late May 2013. The trailer featured the menu music of the video game "", composed by Michael McCann.


title: After Earth

text: In a stark contrast to his previous films, Shyamalan's name was notably absent from several trailers, TV commercials, and marketing signage. Instead, Sony Pictures opted to feature Will and Jaden Smith prominently in the marketing campaign. Sony's worldwide marketing and distribution chairman, Jeff Blake, said that "Night is, without a doubt, a world-class filmmaker who we were thrilled to team up with on this project," but "Together, we decided to focus our campaign on both the action and both Will and Jaden given that 'After Earth' is an adventure story of a father and son." Alex Suskind of Moviefone pointed out to Shyamalan that "After Earth" was not being marketed on the strength of his name unlike his previous projects, to which he responded, "There's such a specific expectation that comes with a name. It's nice to have people watch the movie and then have them talk about the storyteller; it's a healthy balance."


title: After Earth

text: On April 24, XPRIZE, Sony and Overbrook launched the XPRIZE After Earth Challenge, a robotics competition to promote the May 31 release of "After Earth".


title: After Earth

text: The film premiered on May 29 at Ziegfeld Theatre in New York City, with a wide variety of celebrities attending including Bruce Willis, 50 Cent, Spike Lee, and Justin Bieber. Canadian comedian Russell Peters who made fun of Shyamalan when accepting the Razzie Award on his behalf for "The Last Airbender" also attended and even posed with Shyamalan.


title: After Earth

text: Sony Electronics hosted an exclusive 4K screening of "After Earth" at the Paramount Studios Theater on Friday May 31 during the 2013 Cine Gear Expo in Hollywood. The event was held for registered Cine Gear Expo attendees and Sony guests from 6:30-9:30 pm followed by a panel discussion with the filmmakers and production team. After guests filled the 500-plus-seat theater, a second screening was held on Saturday, June 1, 2013, in order to accommodate additional guests from 7:30 pm to 9:30 pm.


title: After Earth

text: On June 6, the European Space Agency (ESA) partnered with Sony Pictures International to support the release of the film, stating that it shares common themes in the film of concern for Earth's future and educating the next generation. ESA and Sony are holding the "After Earth" competition to win the opportunity to go to Bordeaux, France, and have a 'space experience' in weightlessness on a 'parabolic' flight on Novespace's ZERO-G aircraft. The winner would have received paid travel expenses to and from Bordeaux and one night's accommodation for two people and would only be eligible to participate in the reduced gravity aircraft on October 25 following a medical exam.


title: After Earth

text: "After Earth: Innocence" by Michael Jan Friedman and Robert Greenberger, illustrated by Benito Lobel. "Innocence" is a prequel comic book to "After Earth" released by Del Rey Books on November 14, 2012.


title: After Earth

text: "After Earth: United Ranger Corps Survival Manual" is an illustrated manual that describes the After Earth universe from the history of the United Ranger Corps written by Robert Greenberger. It was published through Insight Editions LLC and released on May 21, 2013. The book also follows humanity's exodus from Earth, and the ongoing battle against the Skrel. It contains the secrets of ghosting, the mastery of the cutlass, a schematic of the Ranger base, a complete guide to the highly evolved animals of Earth, and a handwritten journal entry from Cypher Raige.


title: After Earth

text: "After Earth: A Perfect Beast" ("The official prequel novel of the epic film "After Earth"") by Michael Jan Friedman, Robert Greenberger, and Peter David is set nearly 600 years after humanity finds, and colonizes, the planet Nova Prime. The paperback book, published by Del Rey Books on April 30, 2013, is set about 300 years after the last Skrel attack and the Rangers are in danger of being disbanded. Then, the Skrel attack with a new weapon—a bioweapon. The book also contains supplemental stories set just over 400 years further into the future. Main focus is on the "Raige" family and their Ranger heritage.


title: After Earth

text: "After Earth: Kitai's Journal" written by Christine Peymani and illustrated by Jason A. Katzenstein is a paperback book with black-and-white illustrations for younger readers released by HarperCollins on May 21, 2013.


title: After Earth

text: "After Earth: The Official Movie Novelization" by Peter David was released in paperback by publishing company Del Rey Books on May 28, 2013. The book features an expanded story of the film as well as supplemental stories.


title: After Earth

text: During its opening weekend, "After Earth" took in $27.5 million in box office receipts in the United States and Canada. Sony Pictures projected a launch of around $38 million, but the actual number was 17% lower than the lowest pre-release expectation of $33 million. It finished in third place behind "Fast & Furious 6", an action film, and "Now You See Me", a caper film. Taking into account the popularity of principal actor Will Smith, the disappointing finish led "The Wall Street Journal" to call it a "flop". Ray Subers of Box Office Mojo noted the $27 million weekend placed it between 2 sci-fi flops of 2012 films with 200 million-plus budgets, "Battleship" ($25.5 million) and "John Carter" ($30.2 million), and also drew half of the co-stars' previous openings, Will Smith's "Men in Black 3" ($54.6 million) and Jaden Smith's "The Karate Kid" ($55.7 million). Scott Mendelson from "Forbes" argued that Sony made a mistake of not using M. Night Shyamalan's name to market the film, writing, "His name on the marquee reflects that you're not going to get a conventional genre film, that there may be something else up its sleeve."


title: After Earth

text: Sony Pictures spokesman Steve Elzer said a weekend take of about $30 million in the United States and Canada would be a solid number for a movie that is not a branded sequel. Sony distribution chief Rory Bruer said "Certainly we would have liked to have done more, but this was always going to be a worldwide play." "The Hollywood Reporter" reported Sony insiders also estimated a potential loss at about $20 million if the film does not gross high overseas, though estimates of top executives at several other rival studios are much higher. The film ended up losing on about $30 million overseas and rival top executives were then proven right. On "Jimmy Kimmel Live!", Will Smith admitted he was also disappointed with the box office performance and joked "Here's how I think about it, Jimmy, let's be honest. Three is the new one. You know how many ones it takes to make a 3?" and "It's been almost, like, in over 2 decades since I had a movie that wasn't number one! ... That's over now, buddy! Thanks!"


title: After Earth

text: On the worldwide release the following week, "After Earth" took in an estimated $45.5 million in 60 overseas markets, narrowly beating "Fast & Furious 6" estimates of $45.3 million for the No. 1 spot at the international box office. Including the film's launch in South Korea, "After Earth" made an estimated total of $48.6 million at the international box office, bringing its worldwide gross to an estimated $95,192,000. Sources for Sony Pictures International Releasing said the overall launch was bigger than debuts in the same territories of "Oblivion" ($45.1 million), "The Last Airbender" ($42.7 million) and Jaden Smith vehicle "The Karate Kid" ($32.3 million). Sony distribution chief Rory Bruer said that Sony was happy with the overseas opening and expects much of the film's ticket sales to come from international markets and "It definitely was the exciting start we were looking for internationally." The film's final numbers were $60.5 million in North America and $243.8 million worldwide.


title: After Earth

text: On Rotten Tomatoes, the film has an approval rating of 11% based on 211 reviews and an average rating of 3.90/10. The website's critical consensus reads, ""After Earth" is a dull, ploddingly paced exercise in sentimental sci-fi—and the latest setback for director M. Night Shyamalan's once-promising career." On Metacritic, the film has a score of 33 out of 100 based on 41 critics, indicating "generally unfavorable reviews". Audiences polled by CinemaScore gave the film an average grade of "B" on an A+ to F scale.


title: After Earth

text: Joe Morgenstern, film critic for "The Wall Street Journal", opened his review by asking: "Is "After Earth" the worst movie ever made?" His answer was "Maybe not; there's always "Battlefield Earth" to remind us how low the bar can go." Like Morgenstern, Manohla Dargis of "The New York Times" made note of the film's use of central themes in Scientology before concluding the film was nothing more than a "big-screen vanity project". "Los Angeles Times" reviewer Betsy Sharkey wondered how the elder Smith could have gone from the charismatic performance in the serious film "The Pursuit of Happyness", also co-starring his son, to the performance in "After Earth". She also saw compounding problems in the creative process leading to a lack of subtlety and nuance: "The script has no nuance, none. And when Shyamalan moves into the director's chair, the script problems are magnified." Scott Foundas of "Variety" opined that the film was further proof that Shyamalan had become a "director-for-hire", with "his disinterest palpable from first frame to last". Peter Bradshaw of "The Guardian" gave the film one star out of five, calling it "another uncompromisingly terrible film ... featuring a triple-whammy of abysmal acting, directing and story" and saying that Jaden Smith "plays the role throughout with a face like a smacked bum" and "Kitai [Jaden Smith's character] must be like his dad: show no fear. Or any emotion. Or any acting talent of any sort."


title: After Earth

text: Matt Zoller Seitz of RogerEbert.com awarded the film 3.5 stars out of 4 and commented that the movie is "a moral tale disguised as a sci-fi blockbuster. It's no classic, but it's a special movie: spectacular and wise." Jim Vejvoda of IGN awarded the film a 6.7 out of 10 and commented, "M. Night Shyamalan isn't quite back in top form here, but "After Earth" is certainly the best movie he's made in years." Charlie Jane Anders of Io9 commented that "Having suffered through "Last Airbender", I can attest that this film is no "Last Airbender"... "After Earth" stays grounded, and manages to tell a pretty decent story."


title: After Earth

text: The special effects received a mixed response. Rene Rodriguez of "The Miami Herald" said that "the CGI creatures in the film look as fake as the monkeys in "Indiana Jones and the Kingdom of the Crystal Skull"". Charlie McCollum of the "San Jose Mercury News" called them "surprisingly unconvincing, a step or two above the effects in those deliberately cheese ball sci-fi flicks the Syfy channel shows on Saturday night." Michael O'Sullivan of "The Washington Post" called the production design "blandly generic" and the special effects, props and costumes "cheap and slapdash-looking". However, Austin Kennedy of "Film Geek Central" said the special effects were "top-notch", John Depko and Susanne Perez of "Daily Pilot" called them "impressive", Nathan Duke of "Patch Media" said they were "impressive enough", and Peter Feldman of "The Citizen" described them as "solid".


title: After Earth

text: American astronaut Buzz Aldrin said the movie is "quite action packed" and a "touching father/son story" but is not realistic because "there was a lot of noise. In space, you don't get that much noise," a quote that is highly cited in the news and misconstrued as him nitpicking or panning the film. Aldrin was impressed by the set design stating that "the scenes of the cities were really remarkable" but differed significantly from his experience on the moon, which he described as "'magnificent desolation' in contrast to the magnificent experience that humanity could move itself ahead to get to the moon."


title: After Earth

text: In a 2015 interview with "Esquire", Smith called "After Earth" "the most painful failure in his career" and expressed regret over leading his son into the film. He also unfavorably compared the experience to "Wild Wild West" (1999), which also underperformed expectations at the box office.


title: After Earth

text: Ryan Nakashima of Associated Press was generally impressed with the film's 4K resolution picture quality, though the visual-effects shots that composed about a third of the movie were done in 2K resolution to save on cost and time. Nakashima commented "I could see details I've never noticed before—the actors' tiny skin imperfections, or Smith's salt-and-pepper whiskers. In a distant shot of Smith's son Jaden running down a riverbed, I was struck by how many small rocks were defined clearly from such a distance. Yet other shots that included computer-generated cityscapes or otherworldly creatures looked less sharp." The cinematographer Peter Suschitzky was apologetic about that, saying "The movie is only half in true 4K. I'm sad about that. It still looks good."


title: After Earth

text: Scott Wilkinson of AVS was similarly impressed by the visual effects (though he did not enjoy the movie itself): "Even sitting too far away, the movie itself looked gorgeous—sharp as a tack with beautiful colors. The smallest details, such as Jaden Smith's character in the far distance, somehow looked clearer than I would have expected under normal circumstances; I got the distinct impression that the image could have been blown up by quite a bit and no detail would have been lost. The CGI animals did look a bit artificial, but that didn't bother me very much at all."


title: After Earth

text: Some critics were struck by what they saw as parallels in the movie's plot, dialogue and imagery with the Scientology teachings of L. Ron Hubbard, particularly those in "" and "Dianetics: The Original Thesis". Similarly, Peter Travers of "Rolling Stone" compared the film to the "flop" "Battlefield Earth", describing the film as "an unholy mess of platitudes and posturing" that wastes the talents and charm of Will Smith. Pointing out Smith's alleged ties to Scientology, including his funding of New Village Leadership Academy, a school that uses Study Tech as its teaching method, Matt Patches of "Vulture" declared the movie probably the clearest evidence of Smith's investment in Scientology, and detailed how he saw the film paralleling its teachings. "The Hollywood Reporter" published a guest-column review written by former Scientology member Marc Headley which pointed out similar parallels.


title: After Earth

text: David S. Touretzky, a research professor at Carnegie Mellon and a well-known expert on and critic of Scientology dismissed these perceived parallels: "I don't see any Scientology content at all in this movie." He told Rich Juzwiak of Gawker:


title: After Earth

text: Touretzky also addressed multiple points made by the Scientology hypothesis including the film's marketing materials prominently featuring a volcano:


title: After Earth

text: A parody website "cheerupwillsmith.com", which was created for the purpose of cheering up Will Smith with the perceived failure of "After Earth", gained some attention in the media. Flyers were also posted in East Village, Manhattan requesting Scientology members to see "After Earth" a minimum of three times and then upload a positive video for Will Smith on that website. The site has a video mockumentary of two Sea Org members, along their way to see "After Earth", recording video praises for Will Smith from strangers and cajoling them into signing a billion-year contract with the Church of Scientology. When they delivered the signatures to a local branch of the church near Times Square, a church representative told them they were impersonating the church and threatened to call the police if they do not leave. The video and the site was created by Jason Selvig and Davram Stiefler of the comedy duo "The Good Liars" who had previously pretended to be Time Warner Cable representatives asking people how they can make service worse for customers.


title: After Earth

text: The Church of Scientology International branded the Scientology claims as "silly nonsense" and a myth launched by a handful of self-promoters. The church's director of public affairs, Karin Pouw, stated to "TheImproper" magazine that "The film and its story line contain themes common to many of the world's philosophies, not unique to Scientology." While Pouw did not dispute the similarities, she countered that overcoming fear has been a universal theme in stories for thousands of years as well central to countless film plots. She noted the same logic would seemingly make "" a Scientology-themed movie, which includes the dialogue, "Fear is the path to the Dark Side. Fear leads to anger, anger leads to hate, hate leads to suffering." Later, domain registrar and web-hosting company Go Daddy took down "cheerupwillsmith.com" citing "Copyright Infringement, Trademark Infringement, and False Identity." Joe Kloc of "The Daily Dot" presumes the complaints came from the Church of Scientology.


title: After Earth

text: There was heavy criticism of Jaden Smith's role in the film. Christopher Orr of "The Atlantic" stated, "He is entirely lacking in the big-screen charisma that made his father one of Hollywood's major stars." Gary Wolcott of "Tri-City Herald" commented that "the 15-year old Jaden doesn't appear to demonstrate much talent and has zero charisma." Alex Pappademas of Grantland referred to "After Earth" as a "parade-float tribute to nepotism." Mikhail Lecaros of GMA calls the movie "devoid of common sense and purpose (save for nepotism)."


title: After Earth

text: In response to the nepotism allegations, Gary Susman of "Time" magazine argued, "In Hollywood, such nepotism is no sin; in fact, it's often a selling point." David S. Cohen of "Variety" pointed out that "putting family members into projects is hardly new, yet it rarely inspires such vituperation. Abena Agyeman-Fisher of NewsOne.com suggested that the allegations were thinly veiled racism and an example of a double standard being applied to black people. However Charlie Lyne of "The Guardian" writes that nepotism has traditionally carried a stigma.


title: After Earth

text: In March 2018, it was revealed that "After Earth" was intended to be the first installment of a new franchise. Pitched to the studio by Will Smith, the intention was to launch a multimedia franchise titled "1000 AE". Plans were originally for "After Earth" to be followed by a sequel, a live action television series, an animated television series, webisodes, mobisodes, a video game, consumer products, theme-park attractions, documentaries, comics, an educational program collaboration in partnership with NASA, cologne and perfume lines, and a social media platform. Though Smith wanted "1000 AE" to be an immersive experience for the audience, the movie ultimately was poorly received and lost money at the box office. All plans for a continuation were abandoned.


title: Epoxy

text: Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also collectively called "epoxy". The IUPAC name for an epoxide group is an oxirane.


title: Epoxy

text: Epoxy resins may be reacted (cross-linked) either with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols and thiols (usually called mercaptans). These co-reactants are often referred to as hardeners or curatives, and the cross-linking reaction is commonly referred to as curing.


title: Epoxy

text: Reaction of polyepoxides with themselves or with polyfunctional hardeners forms a thermosetting polymer, often with favorable mechanical properties and high thermal and chemical resistance. Epoxy has a wide range of applications, including metal coatings, composites, use in electronics, electrical components (e.g. for chips on board ), LEDs, high-tension electrical insulators, paint brush manufacturing, fiber-reinforced plastic materials, and adhesives for structural and other purposes.


title: Epoxy

text: The health risks associated with exposure to epoxy resin compounds include contact dermatitis and allergic reactions, as well as respiratory problems from breathing vapor and sanding dust, especially when not fully cured.


title: Epoxy

text: Condensation of epoxides and amines was first reported and patented by Paul Schlack of Germany in 1934. Claims of discovery of bisphenol-A-based epoxy resins include Pierre Castan in 1943. Castan's work was licensed by Ciba, Ltd. of Switzerland, which went on to become one of the three major epoxy resin producers worldwide. Ciba's epoxy business was spun off as Vantico in the late 1990s, which was subsequently sold in 2003 and became the Advanced Materials business unit of Huntsman Corporation of the United States. In 1946, Sylvan Greenlee, working for the Devoe & Raynolds Company, patented resin derived from bisphenol-A and epichlorohydrin. Devoe & Raynolds, which was active in the early days of the epoxy resin industry, was sold to Shell Chemical; the division involved in this work was eventually sold, and via a series of other corporate transactions is now part of Hexion Inc.


title: Epoxy

text: Most of the commercially used epoxy monomers are produced by the reaction of a compound with acidic hydroxy groups and epichlorohydrin. First a hydroxy group reacts in a coupling reaction with epichlorohydrin, followed by dehydrohalogenation. Epoxy resins produced from such epoxy monomers are called glycidyl-based epoxy resins. The hydroxy group may be derived from aliphatic diols, polyols (polyether polyols), phenolic compounds or dicarboxylic acids. Phenols can be compounds such as bisphenol A and novolak. Polyols can be compounds such as 1,4-butanediol. Di- and polyols lead to glycidyl ethers. Dicarboxylic acids such as hexahydrophthalic acid are used for diglycide ester resins. Instead of a hydroxy group, also the nitrogen atom of an amine or amide can be reacted with epichlorohydrin.


title: Epoxy

text: The other production route for epoxy resins is the conversion of aliphatic or cycloaliphatic alkenes with peracids: In contrast to glycidyl-based epoxy resins, this production of such epoxy monomers does not require an acidic hydrogen atom but an aliphatic double bond.


title: Epoxy

text: The most common epoxy resins are based on reacting epichlorohydrin (ECH) with bisphenol A,  resulting in a different chemical substance known as bisphenol A diglycidyl ether (commonly known as BADGE or DGEBA). Bisphenol A-based resins are the most widely commercialised resins but also other bisphenols are analogously reacted with epichlorohydrin, for example Bisphenol F.


title: Epoxy

text: In this two-stage reaction, epichlorohydrin is first added to bisphenol A (bis(3-chloro-2-hydroxy-propoxy)bisphenol A is formed), then a bisepoxide is formed in a condensation reaction with a stoichiometric amount of sodium hydroxide. The chlorine atom is released as sodium chloride (NaCl) and the hydrogen atom as water.


title: Epoxy

text: Higher molecular weight diglycidyl ethers (n ≥ 1) are formed by the reaction of the bisphenol A diglycidyl ether formed with further bisphenol A, this is called prepolymerization:


title: Epoxy

text: A product comprising a few repeat units ("n" = 1 to 2) is a viscous, clear liquid; this is called a liquid epoxy resin. A product comprising more repeating units ("n" = 2 to 30) is at room temperature a colourless solid, which is correspondingly referred to as solid epoxy resin.


title: Epoxy

text: Instead of bisphenol A, other bisphenols (especially bisphenol F) or brominated bisphenols (e. g. tetrabromobisphenol A) can be used for the said epoxidation and prepolymerisation. Bisphenol F may undergo epoxy resin formation in a similar fashion to bisphenol A. These resins typically have lower viscosity and a higher mean epoxy content per gram than bisphenol A resins, which (once cured) gives them increased chemical resistance.


title: Epoxy

text: Important epoxy resins are produced from combining epichlorohydrin and bisphenol A to give bisphenol A diglycidyl ethers.


title: Epoxy

text: Increasing the ratio of bisphenol A to epichlorohydrin during manufacture produces higher molecular weight linear polyethers with glycidyl end groups, which are semi-solid to hard crystalline materials at room temperature depending on the molecular weight achieved. This route of synthesis is known as the "taffy" process. The usual route to higher molecular weight epoxy resins is to start with liquid epoxy resin (LER) and add a calculated amount of bisphenol A and then a catalyst is added and the reaction heated to circa . This process is known as "advancement". As the molecular weight of the resin increases, the epoxide content reduces and the material behaves more and more like a thermoplastic. Very high molecular weight polycondensates (ca. 30,000–70,000 g/mol) form a class known as phenoxy resins and contain virtually no epoxide groups (since the terminal epoxy groups are insignificant compared to the total size of the molecule). These resins do however contain hydroxyl groups throughout the backbone, which may also undergo other cross-linking reactions, e.g. with aminoplasts, phenoplasts and isocyanates.


title: Epoxy

text: Epoxy resins are polymeric or semi-polymeric materials or an oligomer, and as such rarely exist as pure substances, since variable chain length results from the polymerisation reaction used to produce them. High purity grades can be produced for certain applications, e.g. using a distillation purification process. One downside of high purity liquid grades is their tendency to form crystalline solids due to their highly regular structure, which then require melting to enable processing.


title: Epoxy

text: An important criterion for epoxy resins is the Epoxy value which is connected to the epoxide group content. This is expressed as the ""epoxide equivalent weight"", which is the ratio between the molecular weight of the Rorar and the number of epoxide groups. This parameter is used to calculate the mass of co-reactant (hardener) to use when curing epoxy resins. Epoxies are typically cured with stoichiometric or near-stoichiometric quantities of hardener to achieve the best physical properties.


title: Epoxy

text: Novolaks are produced by reacting phenol with methanal (formaldehyde). The reaction of epichlorohydrin and novolaks produces novolaks with glycidyl residues, such as epoxyphenol novolak (EPN) or epoxycresol novolak (ECN). These highly viscous to solid resins typically carry 2 to 6 epoxy groups per molecule. By curing, highly cross-linked polymers with high temperature and chemical resistance but low mechanical flexibility are formed due to the high functionality, and hence high crosslink density of these resins.


title: Epoxy

text: There are two common types of aliphatic epoxy resins: those obtained by epoxidation of double bonds (cycloaliphatic epoxides and epoxidized vegetable oils) and those formed by reaction with epichlorohydrin (glycidyl ethers and esters).


title: Epoxy

text: Cycloaliphatic epoxides contain one or more aliphatic rings in the molecule on which the oxirane ring is contained (e.g. 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate). They are produced by the reaction of a cyclic alkene with a peracid (see above). Cycloaliphatic epoxides are characterised by their aliphatic structure, high oxirane content and the absence of chlorine, which results in low viscosity and (once cured) good weather resistance, low dielectric constants and high T. However, aliphatic epoxy resins polymerize very slowly at room temperature, so higher temperatures and suitable accelerators are usually required. Because aliphatic epoxies have a lower electron density than aromatics, cycloaliphatic epoxies react less readily with nucleophiles than bisphenol A-based epoxy resins (which have aromatic ether groups). This means that conventional nucleophilic hardeners such as amines are hardly suitable for crosslinking. Cycloaliphatic epoxides are therefore usually homopolymerized thermally or UV-initiated in an electrophilic or cationic reaction. Due to the low dielectric constants and the absence of chlorine, cycloaliphatic epoxides are often used to encapsulate electronic systems, such as microchips or LEDs. They are also used for radiation-cured paints and varnishes. Due to their high price, however, their use has so far been limited to such applications.


title: Epoxy

text: Epoxidized vegetable oils are formed by epoxidation of unsaturated fatty acids by reaction with peracids. In this case, the peracids can also be formed in situ by reacting carboxylic acids with hydrogen peroxide. Compared with LERs (liquid epoxy resins) they have very low viscosities. If, however, they are used in larger proportions as reactive diluents, this often leads to reduced chemical and thermal resistance and to poorer mechanical properties of the cured epoxides. Large scale epoxidized vegetable oils such as epoxidized soy and lens oils are used to a large extent as secondary plasticizers and cost stabilizers for PVC.


title: Epoxy

text: Aliphatic glycidyl epoxy resins of low molar mass (mono-, bi- or polyfunctional) are formed by the reaction of epichlorohydrin with aliphatic alcohols or polyols (glycidyl ethers are formed) or with aliphatic carboxylic acids (glycidyl esters are formed). The reaction is carried out in the presence of a base such as sodium hydroxide, analogous to the formation of bisphenol A-diglycidyl ether. Also aliphatic glycidyl epoxy resins usually have a low viscosity compared to aromatic epoxy resins. They are therefore added to other epoxy resins as reactive diluents or as adhesion promoters. Epoxy resins made of (long-chain) polyols are also added to improve tensile strength and impact strength.


title: Epoxy

text: A related class is cycloaliphatic epoxy resin, which contains one or more cycloaliphatic rings in the molecule (e.g. 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate). This class also displays lower viscosity at room temperature, but offers significantly higher temperature resistance than the aliphatic epoxy diluents. However, reactivity is rather low compared to other classes of epoxy resin, and high temperature curing using suitable accelerators is normally required. As aromaticity is not present in these materials as it is in Bisphenol A and F resins, the UV stability is considerably improved.


title: Epoxy

text: Halogenated epoxy resins are admixed for special properties, in particular brominated and fluorinated epoxy resins are used.


title: Epoxy

text: Brominated bisphenol A is used when flame retardant properties are required, such as in some electrical applications (e.g. printed circuit boards). The tetrabrominated bisphenol A (TBBPA, 2,2-bis(3,5-dibromophenyl)propane) or its diglycidyl ether, 2,2-bis[3,5-dibromo-4-(2,3-epoxypropoxy)phenyl]propane, can be added to the epoxy formulation. The formulation may then be reacted in the same way as pure bisphenol A. Some (non-crosslinked) epoxy resins with very high molar mass are added to engineering thermoplastics, again to achieve flame retardant properties.


title: Epoxy

text: Fluorinated epoxy resins have been investigated for some high performance applications, such as the fluorinated diglycidether 5-heptafluoropropyl-1,3-bis[2-(2,3-epoxypropoxy)hexafluoro-2-propyl]benzene. As it has a low surface tension, it is added as a wetting agent (surfactant) for contact with glass fibres. Its reactivity to hardeners is comparable to that of bisphenol A. When cured, the epoxy resin leads to a thermosetting plastic with high chemical resistance and low water absorption. However, the commercial use of fluorinated epoxy resins is limited by their high cost and low T.


title: Epoxy

text: Epoxy resins diluents are typically formed by glycidylation of aliphatic alcohols or polyols and also aromatic alcohols. The resulting materials may be monofunctional (e.g. dodecanol glycidyl ether), difunctional (1,4-Butanediol diglycidyl ether), or higher functionality (e.g. trimethylolpropane triglycidyl ether). These resins typically display low viscosity at room temperature (10–200 mPa.s) and are often referred to as reactive diluents. They are rarely used alone, but are rather employed to modify (reduce) the viscosity of other epoxy resins. This has led to the term ‘modified epoxy resin’ to denote those containing viscosity-lowering reactive diluents. The use of the diluent does effect mechanical properties and microstructure of epoxy resins. Mechanical properties of epoxy resins are generally not improved by use of diluents. Biobased epoxy diluents are also available.


title: Epoxy

text: Glycidylamine epoxy resins are higher functionality epoxies which are formed when aromatic amines are reacted with epichlorohydrin. Important industrial grades are triglycidyl-"p"-aminophenol (functionality 3) and "N","N","N"′,"N"′-tetraglycidyl-bis-(4-aminophenyl)-methane (functionality 4). The resins are low to medium viscosity at room temperature, which makes them easier to process than EPN or ECN resins. This coupled with high reactivity, plus high temperature resistance and mechanical properties of the resulting cured network makes them important materials for aerospace composite applications.


title: Epoxy

text: There are several dozen chemicals that can be used to cure epoxy, including amines, imidazoles, anhydrides and photosensitive chemicals. The study of epoxy curing is usually caried out by using Differential scanning calorimetry.


title: Epoxy

text: In general, uncured epoxy resins have only poor mechanical, chemical and heat resistance properties. However, good properties are obtained by reacting the linear epoxy resin with suitable curatives to form three-dimensional cross-linked thermoset structures. This process is commonly referred to as curing or gelation process. Curing of epoxy resins is an exothermic reaction and in some cases produces sufficient heat to cause thermal degradation if not controlled. Curing does induce residual stress in epoxy systems which have been studied. They may be alleviated with flexibilisers.


title: Epoxy

text: Curing may be achieved by reacting an epoxy with itself (homopolymerisation) or by forming a copolymer with polyfunctional curatives or "hardeners". This curing is what produces the qualities of the substance such as resistance, durability, versatility, and adhesion. In principle, any molecule containing a reactive hydrogen may react with the epoxide groups of the epoxy resin. Common classes of hardeners for epoxy resins include amines, acids, acid anhydrides, phenols, alcohols and thiols. Relative reactivity (lowest first) is approximately in the order: phenol < anhydride < aromatic amine < cycloaliphatic amine < aliphatic amine < thiol.


title: Epoxy

text: While some epoxy resin/ hardener combinations will cure at ambient temperature, many require heat, with temperatures up to being common, and up to for some specialist systems. Insufficient heat during cure will result in a network with incomplete polymerisation, and thus reduced mechanical, chemical and heat resistance. Cure temperature should typically attain the glass transition temperature (T) of the fully cured network in order to achieve maximum properties. Temperature is sometimes increased in a step-wise fashion to control the rate of curing and prevent excessive heat build-up from the exothermic reaction.


title: Epoxy

text: Hardeners which show only low or limited reactivity at ambient temperature, but which react with epoxy resins at elevated temperature are referred to as "latent hardeners". When using latent hardeners, the epoxy resin and hardener may be mixed and stored for some time prior to use, which is advantageous for many industrial processes. Very latent hardeners enable one-component (1K) products to be produced, whereby the resin and hardener are supplied pre-mixed to the end user and only require heat to initiate curing. One-component products generally have shorter shelf-lives than standard 2-component systems, and products may require cooled storage and transport.


title: Epoxy

text: The epoxy curing reaction may be accelerated by addition of small quantities of accelerators. Tertiary amines, carboxylic acids and alcohols (especially phenols) are effective accelerators. Bisphenol A is a highly effective and widely used accelerator, but is now increasingly replaced due to health concerns with this substance.


title: Epoxy

text: Epoxy resin may be reacted with itself in the presence of an anionic catalyst (a Lewis base such as tertiary amines or imidazoles) or a cationic catalyst (a Lewis acid such as a boron trifluoride complex) to form a cured network. This process is known as catalytic homopolymerisation. The resulting network contains only ether bridges, and exhibits high thermal and chemical resistance, but is brittle and often requires elevated temperature for the curing process, so finds only niche applications industrially.


title: Epoxy

text: Epoxy homopolymerisation is often used when there is a requirement for UV curing, since cationic UV catalysts may be employed (e.g. for UV coatings).


title: Epoxy

text: Polyfunctional primary amines form an important class of epoxy hardeners. Primary amines undergo an addition reaction with the epoxide group to form a hydroxyl group and a secondary amine. The secondary amine can further react with an epoxide to form a tertiary amine and an additional hydroxyl group. Kinetic studies have shown the reactivity of the primary amine to be approximately double that of the secondary amine. Use of a difunctional or polyfunctional amine forms a three-dimensional cross-linked network.


title: Epoxy

text: Aliphatic, cycloaliphatic and aromatic amines are all employed as epoxy hardeners. Amine type hardeners will alter both the processing properties (viscosity, reactivity) and the final properties (mechanical, temperature and heat resistance) of the cured copolymer network. Thus amine structure is normally selected according to the application. Overall reactivity potential for different hardeners can roughly be ordered; aliphatic amines > cycloaliphatic amines > aromatic amines, though aliphatic amines with steric hindrance near the amino groups may react as slowly as some of the aromatic amines. Slower reactivity allows longer working times for processors. Temperature resistance generally increases in the same order, since aromatic amines form much more rigid structures than aliphatic amines. Aromatic amines were widely used as epoxy resin hardeners, due to the excellent end properties when mixed with a parent resin. Over the past few decades concern about the possible adverse health effects of many aromatic amines has led to increased use of aliphatic or cycloaliphatic amine alternatives. Amines are also blended, adducted and reacted to alter properties and these amine resins are more often used to cure epoxy resins than a pure amine such as TETA. Increasingly, water-based polyamines are also used to help reduce the toxicity profile among other reasons.


title: Epoxy

text: Epoxy resins may be thermally cured with anhydrides to create polymers with significant property retention at elevated temperatures for extended periods of time. Reaction and subsequent crosslinking occur only after opening of the anhydride ring, e.g. by secondary hydroxyl groups in the epoxy resin. Homopolymerization may also occur between epoxide and hydroxyl groups. The high latency of anhydride hardeners makes them suitable for processing systems which require addition of mineral fillers prior to curing, e.g. for high voltage electrical insulators. Cure speed may be improved by matching anhydrides with suitable accelerators. For dianhydrides, and to a lesser extent, monoanhydrides, non-stoichiometric, empirical determinations are often used to optimize dosing levels. In some cases, blends of dianhydrides and monoanhydrides can improve metering and mixing with liquid epoxy resins.


title: Epoxy

text: Polyphenols, such as bisphenol A or novolacs can react with epoxy resins at elevated temperatures (), normally in the presence of a catalyst. The resulting material has ether linkages and displays higher chemical and oxidation resistance than typically obtained by curing with amines or anhydrides. Since many novolacs are solids, this class of hardeners is often employed for powder coatings.


title: Epoxy

text: Also known as mercaptans, thiols contain a sulfur which reacts very readily with the epoxide group, even at ambient or sub-ambient temperatures. While the resulting network does not typically display high temperature or chemical resistance, the high reactivity of the thiol group makes it useful for applications where heated curing is not possible, or very fast cure is required e.g. for domestic DIY adhesives and chemical rock bolt anchors. Thiols have a characteristic odour, which can be detected in many two-component household adhesives.


title: Epoxy

text: The applications for epoxy-based materials are extensive and they are considered very versatile. The applications include coatings, adhesives and composite materials such as those using carbon fiber and fiberglass reinforcements (although polyester, vinyl ester, and other thermosetting resins are also used for glass-reinforced plastic). The chemistry of epoxies and the range of commercially available variations allows cure polymers to be produced with a very broad range of properties. They have been extensively used with concrete and cementitious systems. In general, epoxies are known for their excellent adhesion, chemical and heat resistance, good-to-excellent mechanical properties and very good electrical insulating properties. Many properties of epoxies can be modified (for example silver-filled epoxies with good electrical conductivity are available, although epoxies are typically electrically insulating). Variations offering high thermal insulation, or thermal conductivity combined with high electrical resistance for electronics applications, are available.


title: Epoxy

text: As with other classes of thermoset polymer materials, blending different grades of epoxy resin, as well as use of additives, plasticizers or fillers is common to achieve the desired processing or final properties, or to reduce cost. Use of blending, additives and fillers is often referred to as " formulating".


title: Epoxy

text: All quantities of mix generate their own heat because the reaction is exothermic. Large quantities will generate more heat and thus greatly increase the rate of the reaction and so reduce working time (pot-life). So it is good practice to mix smaller amounts which can be used quickly to avoid waste and to be safer. There are various methods of toughening them.


title: Epoxy

text: Two part epoxy coatings were developed for heavy duty service on metal substrates and use less energy than heat-cured powder coatings. These systems provide a tough, protective coating with excellent hardness. One part epoxy coatings are formulated as an emulsion in water, and can be cleaned up without solvents.


title: Epoxy

text: Epoxy coatings are often used in industrial and automotive applications since they are more heat resistant than latex-based and alkyd-based paints. Epoxy paints tend to deteriorate, known as "chalking out", due to UV exposure. Epoxy coatings have also been used in drinking water applications.


title: Epoxy

text: Change in color, known as yellowing, is a common phenomenon for epoxy materials and is often of concern in art and conservation applications. Epoxy resins yellow with time, even when not exposed to UV radiation. Significant advances in understanding yellowing of epoxies were achieved by Down first in 1984 (natural dark aging) and later in 1986 (high-intensity light aging). Down investigated various room-temperature-cure epoxy resin adhesives suitable for use in glass conservation, testing their tendency to yellow. A fundamental molecular understanding of epoxy yellowing was achieved, when Krauklis and Echtermeyer discovered the mechanistic origin of yellowing in a commonly used amine epoxy resin, published in 2018. They found that the molecular reason for epoxy yellowing was a thermo-oxidative evolution of carbonyl groups in the polymeric carbon–carbon backbone via a nucleophilic radical attack.


title: Epoxy

text: Polyester epoxies are used as powder coatings for washers, driers and other "white goods". Fusion Bonded Epoxy Powder Coatings (FBE) are extensively used for corrosion protection of steel pipes and fittings used in the oil and gas industry, potable water transmission pipelines (steel), and concrete reinforcing rebar. Epoxy coatings are also widely used as primers to improve the adhesion of automotive and marine paints especially on metal surfaces where corrosion (rusting) resistance is important. Metal cans and containers are often coated with epoxy to prevent rusting, especially for foods like tomatoes that are acidic. Epoxy resins are also used for decorative flooring applications such as terrazzo flooring, chip flooring, and colored aggregate flooring.


title: Epoxy

text: Epoxies have been modified in a variety of ways, including reacting with fatty acids derived from oils to yield epoxy esters, which were cured the same way as alkyds. Typical ones were L8 (80% linseed) and D4 (40% dehydrated castor oil). These were often reacted with styrene to make styrenated epoxy esters, used as primers. Curing with phenolics to make drum linings, curing esters with amine resins and pre-curing epoxies with amino resins to make resistant top coats. Organic chains maybe used to hydrophobically modify epoxy resins and change their properties. The effect of chain length of the modifiers has been studied.


title: Epoxy

text: One of the best examples was a system of using solvent free epoxies for priming ships during construction, this used a system of hot airless spray with premixing at the head. This obviated the problem of solvent retention under the film, which caused adhesion problems later on.


title: Epoxy

text: Epoxy adhesives are a major part of the class of adhesives called "structural adhesives" or "engineering adhesives" (that includes polyurethane, acrylic, cyanoacrylate, and other chemistries.) These high-performance adhesives are used in the construction of aircraft, automobiles, bicycles, boats, golf clubs, skis, snowboards, and other applications where high strength bonds are required. Epoxy adhesives can be developed to suit almost any application. They can be used as adhesives for wood, metal, glass, stone, and some plastics. They can be made flexible or rigid, transparent or opaque/colored, fast setting or slow setting. Epoxy adhesives are better in heat and chemical resistance than other common adhesives. In general, epoxy adhesives cured with heat will be more heat- and chemical-resistant than those cured at room temperature. The strength of epoxy adhesives is degraded at temperatures above .


title: Epoxy

text: Some epoxies are cured by exposure to ultraviolet light. Such epoxies are commonly used in optics, fiber optics, and optoelectronics.


title: Epoxy

text: Epoxy systems are used in industrial tooling applications to produce molds, master models, laminates, castings, fixtures, and other industrial production aids. This "plastic tooling" replaces metal, wood and other traditional materials, and generally improves the efficiency and either lowers the overall cost or shortens the lead-time for many industrial processes. Epoxies are also used in producing fiber-reinforced or composite parts. They are more expensive than polyester resins and vinyl ester resins, but usually produce stronger and more temperature-resistant thermoset polymer matrix composite parts. Machine bedding to overcome vibrations is a use in the form of epoxy granite.


title: Epoxy

text: Epoxy resins are used as bonding matrix along with glass or carbon fiber fabrics to produce composites with very high strength to weight characteristics, allowing longer and more efficient rotor blades to be produced. In addition, for offshore and onshore wind energy installations, epoxy resins are used as protective coatings on steel towers, base struts and concrete foundations. Aliphatic polyurethane top coats are applied on top to ensure full UV protection, prolong operational lifetimes and lowering maintenance costs. Electric generators, connected via the drivetrain with the rotor blades, convert mechanical wind energy to usable electric energy, and rely on epoxies electrical insulation and high thermal resistance properties. The same applies to transformers, bushings, spacers, and composites cables connecting the windmills to the grid. In Europe, wind energy components account for the largest segment of epoxy applications, about 27% of the market.


title: Epoxy

text: Epoxy resin formulations are important in the electronics industry, and are employed in motors, generators, transformers, switchgear, bushings, insulators, printed wiring boards (PWB), and semiconductor encapsulants. Epoxy resins are excellent electrical insulators and protect electrical components from short circuiting, dust and moisture. In the electronics industry epoxy resins are the primary resin used in overmolding integrated circuits, transistors and hybrid circuits, and making printed circuit boards. The largest volume type of circuit board—an "FR-4 board"—is a sandwich of layers of glass cloth bonded into a composite by an epoxy resin. Epoxy resins are used to bond copper foil to circuit board substrates, and are a component of the solder mask on many circuit boards.


title: Epoxy

text: Flexible epoxy resins are used for potting transformers and inductors. By using vacuum impregnation on uncured epoxy, winding-to-winding, winding-to-core, and winding-to-insulator air voids are eliminated. The cured epoxy is an electrical insulator and a much better conductor of heat than air. Transformer and inductor hot spots are greatly reduced, giving the component a stable and longer life than unpotted product.


title: Epoxy

text: Epoxies can be used to plug selective layers in a reservoir which are producing excessive brine. The technique is named "water shut-off treatment".


title: Epoxy

text: Epoxies are sold in hardware stores, typically as a pack containing separate resin and hardener, which must be mixed immediately before use. They are also sold in boat shops as repair resins for marine applications. Epoxies typically are not used in the outer layer of a boat because they deteriorate by exposure to UV light. They are often used during boat repair and assembly, and then over-coated with conventional or two-part polyurethane paint or marine-varnishes that provide UV protection.


title: Epoxy

text: There are two main areas of marine use. Because of the better mechanical properties relative to the more common polyester resins, epoxies are used for commercial manufacture of components where a high strength/weight ratio is required. The second area is that their strength, gap filling properties and excellent adhesion to many materials including timber have created a boom in amateur building projects including aircraft and boats.


title: Epoxy

text: Normal gelcoat formulated for use with polyester resins and vinylester resins does not adhere to epoxy surfaces, though epoxy adheres very well if applied to polyester resin surfaces. "Flocoat" that is normally used to coat the interior of polyester fibreglass yachts is also compatible with epoxies.


title: Epoxy

text: Epoxy materials tend to harden somewhat more gradually, while polyester materials tend to harden quickly, particularly if a lot of catalyst is used. The chemical reactions in both cases are exothermic.


title: Epoxy

text: While it is common to associate polyester resins and epoxy resins, their properties are sufficiently different that they are properly treated as distinct materials. Polyester resins are typically low strength unless used with a reinforcing material like glass fibre, are relatively brittle unless reinforced, and have low adhesion. Epoxies, by contrast, are inherently strong, somewhat flexible and have excellent adhesion. However, polyester resins are much cheaper.


title: Epoxy

text: Epoxy resins typically require a precise mix of two components which form a third chemical to get the stated properties. Depending on the properties required, the ratio may be anything from 1:1 or over 10:1, but in usually they must be mixed exactly. The final product is then a precise thermoset plastic. Until they are mixed the two elements are relatively inert, although the 'hardeners' tend to be more chemically active and should be protected from the atmosphere and moisture. The rate of the reaction can be changed by using different hardeners, which may change the nature of the final product, or by controlling the temperature.


title: Epoxy

text: By contrast, polyester resins are usually made available in a 'promoted' form, such that the progress of previously-mixed resins from liquid to solid is already underway, albeit very slowly. The only variable available to the user is to change the rate of this process using a catalyst, often Methyl-Ethyl-Ketone-Peroxide (MEKP), which is very toxic. The presence of the catalyst in the final product actually detracts from the desirable properties, so that small amounts of catalyst are preferable, so long as the hardening proceeds at an acceptable pace. The rate of cure of polyesters can therefore be controlled by the amount and type of catalyst as well as by the temperature.


title: Epoxy

text: As adhesives, epoxies bond in three ways: a) Mechanically, because the bonding surfaces are roughened; b) by proximity, because the cured resins are physically so close to the bonding surfaces that they are hard to separate; c) ionically, because the epoxy resins form ionic bonds at an atomic level with the bonding surfaces. This last is substantially the strongest of the three. By contrast, polyester resins can only bond using the first two of these, which greatly reduces their utility as adhesives and in marine repair.


title: Epoxy

text: Epoxies have been researched and used for construction for a few decades. Although they increase cost of mortars and concrete when used as an additive, they enhance properties. Research is ongoing to investigate the use of epoxies and other recycled plastics in mortars to enhance properties and recycle waste. Densifying plastic materials such as PET and plastic bags and then using them to partially replace aggregate and depolymerizing PET to use as a polymeric binder in addition to epoxy to enhance concrete are actively being studied.


title: Epoxy

text: In the aerospace industry, epoxy is used as a structural matrix material which is then reinforced by fiber. Typical fiber reinforcements include glass, carbon, Kevlar, and boron.


title: Epoxy

text: Epoxies are also used as a structural glue. Materials like wood, and others that are 'low-tech' are glued with epoxy resin. Epoxies generally out-perform most other resin types in terms of mechanical properties and resistance to environmental degradation.


title: Epoxy

text: Water-soluble epoxies such as Durcupan are commonly used for embedding electron microscope samples in plastic so they may be sectioned (sliced thin) with a microtome and then imaged.


title: Epoxy

text: Epoxy resin, mixed with pigment, may be used as a painting medium, by pouring layers on top of each other to form a complete picture. It is also used in jewelry, as a doming resin for decorations and labels, and in decoupage type applications for art, countertops, and tables. It has been used and studied for art and historic structure preservation.


title: Epoxy

text: The global epoxy resin market was valued at approximately $8 billion in 2016. The epoxy resin market is dominated by the Asia-Pacific region, which contributes 55.2% of the total market share. China is the major producer and consumer globally, consuming almost 35% of the global resin production. The global market is made up of approximately 50–100 manufacturers of basic or commodity epoxy resins and hardeners. In Europe, about 323,000 tonnes of epoxy resin were manufactured in 2017 generating some €1,055 million in sales. Germany is the largest market for epoxy resins in Europe, followed by Italy, France, the UK, Spain, the Netherlands and Austria.


title: Epoxy

text: These commodity epoxy manufacturers mentioned above typically do not sell epoxy resins in a form usable to smaller end users, so there is another group of companies that purchases epoxy raw materials from the major producers and then compounds (blends, modifies, or otherwise customizes) epoxy systems from these raw materials. These companies are known as "formulators". The majority of the epoxy systems sold are produced by these formulators and they comprise over 60% of the dollar value of the epoxy market. There are hundreds of ways that these formulators can modify epoxies—by adding mineral fillers (talc, silica, alumina, etc.), by adding flexibilizers, viscosity reducers, colorants, thickeners, accelerators, adhesion promoters, etc. These modifications are made to reduce costs, to improve performance, and to improve processing convenience. As a result, a typical formulator sells dozens or even thousands of formulations—each tailored to the requirements of a particular application or market.


title: Epoxy

text: The raw materials for epoxy resin production are today largely petroleum derived, although some plant derived sources are now becoming commercially available (e.g. plant derived glycerol used to make epichlorohydrin).


title: Epoxy

text: As there is a general trend to renewable and "green" sources and greater use of biobased materials, research is ongoing in the epoxy arena too. Waterborne epoxy paints have been around since the 1970s and research is ongoing. There is also movement to use waste as well as recycled raw materials where possible. Waste granite filings are produced in the mining industry. Research is being done on innovative solutions such as using waste granite powders in epoxy resins and designing binders for coatings based on this.


title: Epoxy

text: Liquid epoxy resins in their uncured state are mostly classed as irritant to the eyes and skin, as well as toxic to aquatic organisms. Solid epoxy resins are generally safer than liquid epoxy resins, and many are classified non-hazardous materials. One particular risk associated with epoxy resins is sensitization. The risk has been shown to be more pronounced in epoxy resins containing low molecular weight epoxy diluents. Exposure to epoxy resins can, over time, induce an allergic reaction. Sensitization generally occurs due to repeated exposure (e.g. through poor working hygiene or lack of protective equipment) over a long period of time. Allergic reaction sometimes occurs at a time which is delayed several days from the exposure. Allergic reaction is often visible in the form of dermatitis, particularly in areas where the exposure has been highest (commonly hands and forearms). Epoxy use is a main source of occupational asthma among users of plastics. Safe disposal also needs considering but usually involves deliberate curing to produce solid rather than liquid waste.


title: Radiation

text: In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:


title: Radiation

text: Radiation is often categorized as either "ionizing" or "non-ionizing" depending on the energy of the radiated particles. Ionizing radiation carries more than 10 eV, which is enough to ionize atoms and molecules and break chemical bonds. This is an important distinction due to the large difference in harmfulness to living organisms. A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, and photons, respectively. Other sources include X-rays from medical radiography examinations and muons, mesons, positrons, neutrons and other particles that constitute the secondary cosmic rays that are produced after primary cosmic rays interact with Earth's atmosphere.


title: Radiation

text: Gamma rays, X-rays and the higher energy range of ultraviolet light constitute the ionizing part of the electromagnetic spectrum. The word "ionize" refers to the breaking of one or more electrons away from an atom, an action that requires the relatively high energies that these electromagnetic waves supply. Further down the spectrum, the non-ionizing lower energies of the lower ultraviolet spectrum cannot ionize atoms, but can disrupt the inter-atomic bonds which form molecules, thereby breaking down molecules rather than atoms; a good example of this is sunburn caused by long-wavelength solar ultraviolet. The waves of longer wavelength than UV in visible light, infrared and microwave frequencies cannot break bonds but can cause vibrations in the bonds which are sensed as heat. Radio wavelengths and below generally are not regarded as harmful to biological systems. These are not sharp delineations of the energies; there is some overlap in the effects of specific frequencies.


title: Radiation

text: The word "radiation" arises from the phenomenon of waves "radiating" (i.e., traveling outward in all directions) from a source. This aspect leads to a system of measurements and physical units that are applicable to all types of radiation. Because such radiation expands as it passes through space, and as its energy is conserved (in vacuum), the intensity of all types of radiation from a point source follows an inverse-square law in relation to the distance from its source. Like any ideal law, the inverse-square law approximates a measured radiation intensity to the extent that the source approximates a geometric point.


title: Radiation

text: Radiation with sufficiently high energy can ionize atoms; that is to say it can knock electrons off atoms, creating ions. Ionization occurs when an electron is stripped (or "knocked out") from an electron shell of the atom, which leaves the atom with a net positive charge. Because living cells and, more importantly, the DNA in those cells can be damaged by this ionization, exposure to ionizing radiation increases the risk of cancer. Thus "ionizing radiation" is somewhat artificially separated from particle radiation and electromagnetic radiation, simply due to its great potential for biological damage. While an individual cell is made of trillions of atoms, only a small fraction of those will be ionized at low to moderate radiation powers. The probability of ionizing radiation causing cancer is dependent upon the absorbed dose of the radiation, and is a function of the damaging tendency of the type of radiation (equivalent dose) and the sensitivity of the irradiated organism or tissue (effective dose).


title: Radiation

text: If the source of the ionizing radiation is a radioactive material or a nuclear process such as fission or fusion, there is particle radiation to consider. Particle radiation is subatomic particles accelerated to relativistic speeds by nuclear reactions. Because of their momenta they are quite capable of knocking out electrons and ionizing materials, but since most have an electrical charge, they don't have the penetrating power of ionizing radiation. The exception is neutron particles; see below. There are several different kinds of these particles, but the majority are alpha particles, beta particles, neutrons, and protons. Roughly speaking, photons and particles with energies above about 10 electron volts (eV) are ionizing (some authorities use 33 eV, the ionization energy for water). Particle radiation from radioactive material or cosmic rays almost invariably carries enough energy to be ionizing.


title: Radiation

text: Most ionizing radiation originates from radioactive materials and space (cosmic rays), and as such is naturally present in the environment, since most rocks and soil have small concentrations of radioactive materials. Since this radiation is invisible and not directly detectable by human senses, instruments such as Geiger counters are usually required to detect its presence. In some cases, it may lead to secondary emission of visible light upon its interaction with matter, as in the case of Cherenkov radiation and radio-luminescence.


title: Radiation

text: Ionizing radiation has many practical uses in medicine, research, and construction, but presents a health hazard if used improperly. Exposure to radiation causes damage to living tissue; high doses result in Acute radiation syndrome (ARS), with skin burns, hair loss, internal organ failure, and death, while any dose may result in an increased chance of cancer and genetic damage; a particular form of cancer, thyroid cancer, often occurs when nuclear weapons and reactors are the radiation source because of the biological proclivities of the radioactive iodine fission product, iodine-131. However, calculating the exact risk and chance of cancer forming in cells caused by ionizing radiation is still not well understood and currently estimates are loosely determined by population based data from the atomic bombings of Hiroshima and Nagasaki and from follow-up of reactor accidents, such as the Chernobyl disaster. The International Commission on Radiological Protection states that "The Commission is aware of uncertainties and lack of precision of the models and parameter values", "Collective effective dose is not intended as a tool for epidemiological risk assessment, and it is inappropriate to use it in risk projections" and "in particular, the calculation of the number of cancer deaths based on collective effective doses from trivial individual doses should be avoided."


title: Radiation

text: Ultraviolet, of wavelengths from 10 nm to 125 nm, ionizes air molecules, causing it to be strongly absorbed by air and by ozone (O) in particular. Ionizing UV therefore does not penetrate Earth's atmosphere to a significant degree, and is sometimes referred to as vacuum ultraviolet. Although present in space, this part of the UVA spectrum is not of biological importance, because it does not reach living organisms on Earth.


title: Radiation

text: There is a zone of the atmosphere in which ozone absorbs some 98% of non-ionizing but dangerous UV-C and UV-B. This so-called ozone layer starts at about and extends upward. Some of the ultraviolet spectrum that does reach the ground is non-ionizing, but is still biologically hazardous due to the ability of single photons of this energy to cause electronic excitation in biological molecules, and thus damage them by means of unwanted reactions. An example is the formation of pyrimidine dimers in DNA, which begins at wavelengths below 365 nm (3.4 eV), which is well below ionization energy. This property gives the ultraviolet spectrum some of the dangers of ionizing radiation in biological systems without actual ionization occurring. In contrast, visible light and longer-wavelength electromagnetic radiation, such as infrared, microwaves, and radio waves, consists of photons with too little energy to cause damaging molecular excitation, and thus this radiation is far less hazardous per unit of energy.


title: Radiation

text: X-rays are electromagnetic waves with a wavelength less than about 10 m (greater than 3x10 Hz and 1,240 eV). A smaller wavelength corresponds to a higher energy according to the equation E=h c/λ. ("E" is Energy; "h" is Planck's constant; "c" is the speed of light; "λ" is wavelength.) When an X-ray photon collides with an atom, the atom may absorb the energy of the photon and boost an electron to a higher orbital level or if the photon is extremely energetic, it may knock an electron from the atom altogether, causing the atom to ionize. Generally, larger atoms are more likely to absorb an X-ray photon since they have greater energy differences between orbital electrons. The soft tissue in the human body is composed of smaller atoms than the calcium atoms that make up bone, so there is a contrast in the absorption of X-rays. X-ray machines are specifically designed to take advantage of the absorption difference between bone and soft tissue, allowing physicians to examine structure in the human body.


title: Radiation

text: X-rays are also totally absorbed by the thickness of the earth's atmosphere, resulting in the prevention of the X-ray output of the sun, smaller in quantity than that of UV but nonetheless powerful, from reaching the surface.


title: Radiation

text: Gamma (γ) radiation consists of photons with a wavelength less than 3x10 meters (greater than 10 Hz and 41.4 keV). Gamma radiation emission is a nuclear process that occurs to rid an unstable nucleus of excess energy after most nuclear reactions. Both alpha and beta particles have an electric charge and mass, and thus are quite likely to interact with other atoms in their path. Gamma radiation, however, is composed of photons, which have neither mass nor electric charge and, as a result, penetrates much further through matter than either alpha or beta radiation.


title: Radiation

text: Gamma rays can be stopped by a sufficiently thick or dense layer of material, where the stopping power of the material per given area depends mostly (but not entirely) on the total mass along the path of the radiation, regardless of whether the material is of high or low density. However, as is the case with X-rays, materials with a high atomic number such as lead or depleted uranium add a modest (typically 20% to 30%) amount of stopping power over an equal mass of less dense and lower atomic weight materials (such as water or concrete). The atmosphere absorbs all gamma rays approaching Earth from space. Even air is capable of absorbing gamma rays, halving the energy of such waves by passing through, on the average, .