Polylactide/Biopolyethylene bioblends
In this work, Polylactide/Biopolyethylene blends were developed. Although some studies have been carried out on polylactide/polyethylene blends, none of them has used polyethylene synthesized with raw material obtained from natural sources. Due to the incompatibility between polylactide and polyethylene, E-GMA and EMA-GMA compatibilizers were used. These compatibilizers present glycidyl methacrylate groups in their structure, which may react with the functional end-groups of polylactide. To evaluate the properties, the blends were characterized by mechanical tests, scanning electron microscopy (SEM) and melt flow index (MFI). The results indicated that the compatibilizers played an important role in the blends, interacting with the blends components, modifying the morphology and improving the mechanical properties.
태양선택 흡수면의 Thermal Degradation
When wood is exposed to elevated temperatures, changes can occur in its chemical structure that affect its performance. The extent of the changes depends on the temperature level and the length of time under exposure conditions. The changes in chemical structure may be manifested only as reduced strength, and hydroscopic water and volatile oil weight loss. In contrast, very drastic chemical changes may result in reduced strength and significant carbohydrate weight loss. At temperatures below 100°C, permanent reductions in strength can occur. The magnitude of the reduction depends on the moisture content, heating medium, exposure period and species. The strength degradation is usually not considered to result from the same thermal decomposition of the wood that occurs above 100°C, since no significant carbohydrate weight loss occurs. The strength degradation is probably due to depolymerization reactions, although little research has been done on the chemical mechanism. Reviews by Gerhards (1979, 1982, 1983) and Koch (1985) summarize reduction in strength at temperatures below 100oC (See Strength). If the wood has been treated with a chemical to reduce its flammability, more significant reductions in strength can occur at lower temperatures than for untreated wood. This is due to the presence of chemicals that catalyze the dehydration and depolymerization reactions. A review by Winandy (1987) summarizes the effects of elevated temperatures on strength properties of treated wood. At temperatures above 100oC, chemical bonds begin to break. The rate at which the bonds are broken increases as the temperature increases. Between 100°C and 200oC, noncombustible products, such as carbon dioxide, traces of organic compounds and water vapor, are produced. Above 200oC the celluloses break down, producing tars and flammable volatiles that can diffuse into the surrounding environment. If the volatile compounds are mixed with air and heated to the ignition temperature, combustion reactions occur. The energy from these exothermic reactions radiates to the solid material, thereby propagating the combustion, or pyrolysis, reactions. If the burning mixture accumulates enough energy to emit radiation in the visible spectrum, the phenomenon is known as flaming combustion (see Fire and Wood). Above 450oC all volatile material is gone. The residue that remains is an activated char that can be oxidized to carbon dioxide, carbon monoxide and water vapor. Oxidation of the char is referred to as afterglow. The thermal degradation of wood can be represented by two pathways (Fig. 1), one occurring at high temperatures (>300oC), the other at lower temperatures. These two competing reactions occur simultaneously. Fire retardants work by shifting degradation to the low-temperature pathway.
Nietzsche: Philosopher, Psychologist, Antichrist
This classic is the benchmark against which all modern books about Nietzsche are measured. When Walter Kaufmann wrote it in the immediate aftermath of World War II, most scholars outside Germany viewed Nietzsche as part madman, part proto-Nazi, and almost wholly unphilosophical. Kaufmann rehabilitated Nietzsche nearly single-handedly, presenting his works as one of the great achievements of Western philosophy. Responding to the powerful myths and countermyths that had sprung up around Nietzsche, Kaufmann offered a patient, evenhanded account of his life and works, and of the uses and abuses to which subsequent generations had put his ideas.Without ignoring or downplaying the ugliness of many of Nietzsche's proclamations, he set them in the context of his work as a whole and of the counterexamples yielded by a responsible reading of his books. More positively, he presented Nietzsche's ideas about power as one of the great accomplishments of modern philosophy, arguing that his conception of the "will to power" was not a crude apology for ruthless self-assertion but must be linked to Nietzsche's equally profound ideas about sublimation.He also presented Nietzsche as a pioneer of modern psychology and argued that a key to understanding his overall philosophy is to see it as a reaction against Christianity. Many scholars in the past half century have taken issue with some of Kaufmann's interpretations, but the book ranks as one of the most influential accounts ever written of any major Western thinker.