human
***task***
the task is to summarize an input biomedical literature in six sentences

***input***
the input is a biomedical literature

***output***
the output is the summary of an input biomedical literature in six sentences

***documentation***

***examples***

input: a paper based product typically contains 9099 % cellulose fibers which are the primary structural element and the most important component influencing end use properties . a network of self - bonding cellulose fibers within network structure affects chemical and physical characteristics of the paper products . however , the chemical structure of cellulose is now well established and consists - anhydroglucose units with dominant hydroxyl groups , which are appropriate groups for reactions . these are mainly due to the one primary and two secondary hydroxyl groups in each monomer unit in polymer structure . each of anhydroglucose units are linked together by -1 - 4 glycosidic bonds . due to specific chemical arrangements of cellulose , it is completely linear homopolysacharide and has the ability to form extensive intra and intermolecular hydrogen bonds . because , paper network is composed from randomly laid fibrous ( cellulose ) and non - fibrous ( fillers ) materials , it contains a complicated set of cavity pore channels with a variety of capillary dimensions . however , the structure of paper can be modified during contact of liquids because it disrupts hydrogen bonds , relaxes fibers , and produces dimensional changes in pores and capillaries . if the effect of external pressure is neglected , the washburn equation could be used to describe the rate of capillary rise of fluids into paper . where dl / dt is the rate of penetration of the capillary , l is the distance penetrated into a cylindrical capillary of radius r , in time t , angle between liquid and surface , by a liquid with surface tension lv and viscosity . a number of studies have been conducted on the reasonably explanation for paper - liquid interactions . however , most studies have shown that the chemical and physical properties of fibers ( cellulose ) are reduced upon rewetting . consistently , the decrease of the absorption and strength properties of rewetted fibers because of changes in the basic structure during swelling and reducing fiber bonding potential . it was speculated that during drying , cellulose lose both free and bound water and start to shrink . it has modified to hard and stiff state ( hardening ) that have not reswell properly compare to never dried state . the mechanism of cellulose hardening is complicated and probably related with removal of bound water , lowers the distance between microfibrils and reducing the elasticity of fibrils . as a result of these modifications , the hydrogen bond cross - links could be formed between adjacent microfibrils in cellulose structure . the hydrophilic natures of the cellulose within paper structure are very important for good fiber - fiber bonding . however , the challenging aspects for wetting of papers understand how to increase and control fibers wetting and bonding . it is believed that repeating wetting and drying brings about irreversible changes in cellulose bonding potential . therefore , there is a need to understand more clearly the changes that take place in the rewetted cellulose fibers . these may open the possibility to increase recycling of cellulose based products ( e.g. paper and paperboards ) . moreover , new modified processes , involve various type of organosolv pulping approaches can also be required more detailed information on the effect of solvent systems on cell wall chemical constituents especially on cellulose . the objective of this study is to investigate the influence of various solvent formulations over repeating drying and wetting paper , composed only cellulose , in terms of evaluating chemical and physical properties . the experiments were conducted to ascertain the effect of various solvent formulations on liquid absorption , chemical and strength properties as well as capillary pore structure of papers . whatman filter paper , composed only from cellulose fibers , has completely free of all additives and fillers , was utilized as paper source under laboratory conditions . the whatman filter papers ( no : 1 ) and the chemicals with a purity of 9799 % , used in this study were purchased from yildiz kimya ltd ( ankara - turkey ) and utilized as received . the solvent treatments are designed to evaluate liquid sorption capacity through chemical modification and pore size distribution in paper network after continuously repeating drying and wetting cycles . four different solvents and their appropriate proportion mixtures were utilized in treatments : water ( h2o ) , ethanol ( etoh ) , methanol ( meoh ) , sodium hydroxide ( naoh ) . the constituents of solvent mixtures that paper samples treated at atmospheric conditions are presented in table 1 . five repeating wetting - drying stages were carried out to evaluate some chemical and physical paper properties . the sheets were soaked in the solvents at the atmospheric conditions for 8 hours . at the end of each wetting stage , the sorption properties of the samples were determined in conformity with tappi test method t 441 . but longer time was used to calculate liquid sorption as well as strength properties of samples . the tensile strength and stretch propertiesthis technique was based on the differences between the two type dyes ( direct blue i and fast orange 15 ) molecular size and affinity for cellulose . the dyes were purchased from pylam products co. , inc . , tepme , az , under the commercial names of pontamine fast sky blue 6bx and pontamine fast orange 6rn , respectively . the dyes were used as received , without further purification . the 1 g orange and blue dyewere dissolved in 100 ml distilled water then the dye solutions mixed in a ratio of 1:1 by volume . the small samples ( 1x1 cm ) were first soaked in dye solutions for 1 min and then 1 min in water . after that , they were put on a slide and dried at 75c , examined under a light microscope . direct blue i has a defined chemical structure with a molecular diameter of 1 nm . fast orange 15 dye is a condensation product of 5 - nitro - o - toluenesulfonic acid in aqueous alkali solution and its formula and structure are not well defined . however , it was proposed that the purified fast orange 15 dye has a molecular diameter in the range of 536 nm , which is much larger than the direct blue i molecular size . a shimadzu ir prestige - 21 series ir spectrophotometer was used to evaluate the chemical groups on the untreated and solvent treated papers . figure 1 shows liquid sorption properties of papers which are treated in water ( a ) , ( anhydrous ) ethanol ( b ) , ( anhydrous ) methanol ( c ) , 1 n sodium hydroxide ( d ) , up to five repeating drying and wetting stages . it can be revealed that the highest sorption occured with sample d ( 230.5 % in 1 cycle and 179.8 % in 5 cycle ) followed by sample a ( 182.3 % in 1 cycle and 170.6 % in 5 cycle ) , sample b ( 109.4 % in 1 cycle and 97.6 % in 5 cycle ) , and sample c ( 101.5 % in 1 cycle and 84.3 % in 5 cycle ) , respectively . this is not surprising because a number of researchers have already reported a definite correlation between chemical treatments and sorption properties for cellulosic materials . these reductions can be attributed to a change in the fiber polymer structure , such as hydrogen bonds cross - links or the elimination of h - bonding sites for liquids . because , all the liquids used in this study have hydrogen bonding ability and can penetrate into the paper network structure , followed by substitution of - oh for cellulose to cellulose hydrogen bonds . moreover , the closure of larger pores which do not reopen upon rewetting can be affects of high surface tension forces . this subsequent strain - hardening mechanism and forces may be welded the pores and resist against liquid penetration some degree . these are in good agreement with the results reported by wistara ( 1999 ) that dried fibers with higher initial swelling capacity have lower capability to reswell . however , 1 n sodium hydroxide treated sample ( d ) has considerably higher absorption value than others . after 5 repeating wetting - drying cycle , the sample d shows approximately 6 % higher absorption from sample a , 85 % from sample b and 114 % from sample c , respectively ( figure 1 ) . it can be attributed to reorientation of microfibrils and a better alignment of cellulose chains in sheet network structure that promote additional h - bonding sites for liquid . das and chakraborty ( 2006 ) was found that during alkali treatment , a lattice transformation from cellulose - i to cellulose - ii took place and sodium hydroxide introduces considerable changes in crystallinity and orientation angle within cellulose structure . these can be affects less crystalline region in cellulose hence further h - bonding place for liquids . the marked effect of sodium hydroxide addition to ethanol ( b ) in terms of sorption of paper ( e , f , and g ) is clearly evident in figure 2 . the highest absorption was obtained with sample f ( etoh - naoh 1:3 by vol ) after 1 wetting - drying cycle ( 185.7 % ) and further treatments decresing affects on liquid sorption of papers but they are still considerably higher than only etoh and lower amount naoh including systems . sample f showed approximately 4070 % higher liquid absorption compare to sample b ( 109.4 % ) at similar wetting - drying stages ( figure 2 ) . it seemed as if the increase of the liquid absorption was closely related to naoh content in etoh system and inversely related to wetting - drying stage . the sorption properties of papers at proportional mixture of methanol and sodium hydroxide reaction conditions are shown in figure 3 . similar to ethanol - alkali system , the highest absorption of 162.3 % was also found with sample i ( meoh - naoh 1:3 by vol ) but after 5 wetting - drying stage . one may also observe that extended drying - wetting usually affects 210 % increased liquid absorption properties for sample i. however , it can be realized that the liquid absorption was positively correlated with sodium hydroxide content in methanol system . these comparisons between the treatments and the measured results reveal that the sodium hydroxide response of cellulose can be predicted quite well by proportional mixture with ethanol ( figure 2 ) and methanol ( figure 3 ) . it was reported by rowell that the interaction between cellulosics and organic liquids was mainly influenced by the solvent ph , the molar size , and the hydrogen bonding capacity of the liquid . however , the variable sorption properties of sheets that treated with mixtures of ethanol and methanol with alkali , at similar conditions clearly reveals that the liquid absorption into paper sheet structure closely related to nature of the liquid ( ph ) and its surface tension as revealed in figures 13 . moreover , it has already proposed that swelling and sorption properties of papers in alkali conditions were higher than acidic conditions . this is probably related to fibril openings , which is influences the swelling capacity of cellulose , is an important factor to improve absorption potential of the fibers . watanabe and his group speculated that approximately 37 wt % of adsorbed water was responsible for the stabilization of the h - bond network at the cellulose - water surface . but , all the solvent systems used in this study have hydrogen bonding potential and they can penetrate into the web structure , followed by substitution of - oh for cellulose to cellulose hydrogen bonds . hence , inter and intrachain h - bonds of cellulose can be formed by solvent molecules during absorption . tensile strength of papers have usually used as an indication of the treatment affects on the paper strength derived from factors such as fiber strength , and bonding . the comparative tensile strengths of ten different solvent ( a - j ) treated papers with comparison to control that have strength of 37.3 n / mm are shown in figure 4 . all treatment conditions apparently bring about an effect of decreased strength for papers . after 1 wetting - drying stage , the highest strength loss was observed with sample a ( 16.8 n / mm , 54.9 % ) followed by sample b ( 18.0 n / mm , 51.3 % ) , sample f ( 18.6 n / mm , 50 % ) , respectively . however , the lowest strength found with sample b and d ( 13.0 n / mm , 65 % ) after 5 repeating wetting - drying stage . it is apparent that the treatment conditions were too severe , thus the strength properties of the papers sharply decreased . moreover , the addition of alkali to both ethanol and methanol ( e - j ) seems to have less affect on strength loss on papers . the porous structure of the sheets has a major influence on the penetration of a liquid into network . when paper contact with liquids , they tend to move from large cavities into smaller ones according to their different capillary pressures . it was proposed by atalla that the dehydration process of cellulose promote molecular mobility could result in enhancing levels of molecular organization . however , this molecular organization limits the capacity of fibers to respond to stress in an elastic mode without failure . the strength results found for cellulose paper in this study consisted with this information . when evaluating the tensile strength , also the stretch of paper at break ( elongation % ) should be considered . it is indicative of the ability of paper to conform to a desired property under nonuniform tensile stress . the comparative stretch ( as reported , elongation at break % ) of samples ( a - j ) are shown in figure 5 . it appears that repeated wetting - drying some level affects stretch in either increase and of decrease depends on solvent type and treatment stage . this is somewhat surprising , considering that the strength properties are considerably decreased with all treatments conditions . after 1 wetting - drying stage , the highest stretch improvement was found with sample g ( 26.8 % ) followed by with sample a ( 13.2 % ) , and marginally similar stretch improvements with samples b , c , h , i and j ( 48 % ) , in that order . however , after 5 wetting - drying stage , some papers shows considerably higher stretch than untreated and and / or lower treated samples . the highest stretch , hence , improvement was observed with sample e ( 59.5 % ) followed by sample i ( 49.8 % ) , sample j ( 28.7 % ) , sample h ( 21 % ) , respectively . moreover , samples b , c , d and f show approximately 1827 % stretch loss compare to control . the strength developments as well as physical behavior of papers are very complicated and depend on many factors such as structure of cellulose especially on crystalline region , and h - bonding of randomly laid network elements . but in brief , it is apparent that the strength properties of sheets considerably decrease with liquid treatments especially in acidic environment ( b and c ) but the addition of alkali ( naoh ) to both ethanol and methanol solvents seems to have less effect on strength loss , even some level improvement on stretch of papers realized in various conditions . simons stain is a practical technique for evaluating the pore structure of cellulose fibers , especially in recycling and pulping processes . when a mixture of two dyes ( direct blue i and fast orange 15 ) is applied to fibers , the blue and / or orange dye can absorbs to fibers with depending pore size . for fibers with a various pore size distribution range , the color of the stained fiber can depend on the ratio of surface area accessible to both dyes . the chemical structures of both dyes are shown in figure 6 . table 2 shows a summary of the paper samples obtained from various conditions and their staining properties under light microscope . it is realized that papers obtained from different conditions showed variable intensities of blue and orange stain . however , this rating does not reflect any quantitative measurements and that the comparison should to be made only within each experimental set . after 1 wetting - drying stage , except sample b , other single solvent treated samples ( a , c , d ) shows intensive light blue - orange color . moreover , paper samples that treated with proportional mixtures of etoh , meoh and naoh ( e - j ) have various level intermediate orange to dark orange color . this is clear evidence that alkali addition to acidic condition effects on increase pore size of fibers . because direct blue i has a smaller molecular size ( approx . 1 nm ) and a weaker affinity for cellulose compared to direct orange 15 , which has a larger molecular size ( 536 nm ) and a stronger affinity . but after 5 wetting - drying stage , most of the samples stained dark blue to light blue - orange color with the exception of sample f ( etoh - naoh , 1:3 by vol ) which the fibers stains intermediate orange and slightly dark orange . this is clear evidence that increasing alkali concentration in acidic solvents may be effects restoration of fiber pore size and effects less damaging with continuous drying and wetting . it has already stated above that , direct orange 15 molecules can preferentially be adsorbed on the fiber surface where the pore size is appropriate ( e.g. 5 nm ) for accessing direct orange 15 molecules . for the small capillary pores ( e.g. 5 nm ) , where the direct orange 15 molecules are not accessible , the direct blue i molecules can be adsorbed . therefore , the ratio of adsorbed direct orange 15 to adsorbed direct blue i is anticipated to serve as an indicator of the pore structure , specifically , the pore size population distribution of the paper . simons stain results are usually correlated with strength and sorption properties of papers ( figures 15 ) . the ftir spectra of various level solvent treated paper samples were obtained in range of 4004000 cm . however , the characteristic spectrum of cellulose structure concentrate in the range of 8002000 cm and the major peaks in this range had been identified . the comparative ftir spectra of various solvent treated papers after 5 repeating drying - wetting stage are shown in figure 7 ( a g ) . all spectra exhibit multi - modal absorption in the 6001000 cm region due to oh groups in cellulose . the out - of - plane c - h vibration was assigned at 750 cm . the band at 9001150 cm is attributed to c - c out of the plane stretching , c - c - o stretching at 1060 cm ; c - o - c symmetric stretching 1150 cm ( figure 7a ) . however , the spectra of solvent treated samples ( figure 7d f ) , exhibit the more absorption in the 8001200 cm region relative to the untreated cellulose , where a more complex in - plane oh vibration is dominant . however , the less intense ch2ch2 - vibrations ( 14501700 cm ) and c - c and c - o - c peak areas ( figure 7c , d , g ) indicates the generation of new surface chemistry which is related to the solvent induced / dried chain modification . young ( 1994 ) and weise and paulapuro ( 1996 ) found that drying affects lowering distance between microfibrils and cross - links in cellulose structure . the result found with ftir evaluation of cellulose sheets that treated with various solvents and continuously wetted - dried cycles , support this information . on the basis of ftir measurementsit was concluded that some modification had taken place during solvent diffusion and solvent induced chain modification occurred in cellulose structure . a number of solvent treatment conditions were utilized for evaluating cellulose paper in terms of liquid absorption , strength as well as sheet network structure of papers . it can be revealed that repeating drying and wetting usually affects on decreasing liquid absorption and strength of cellulose papers . these can be attributed to a change in the fiber polymer structure especially elimination of h - bonding sites for liquids . however , liquid absorption was significantly improved by alkali addition to both meoh and etoh solvent systems . ftir measurements indicated some modification had taken place during solvent diffusion and solvent induced chain modification occurred in cellulose structure .
output:

agent
the cellulose paper treated in proportional mixture systems showed higher liquid absorption compare to only etoh and meoh treatments . it was approximately 4070 % and 5091 % higher for etoh - naoh and meoh - naoh treated papers , respectively . all conditions apparently bring about an effect of decreased strength for papers . the lowest tensile strength of 13.0 n / mm was found with etoh and naoh treated samples after 5th repeating wetting - drying stage . but , some conditions gave approximately 2159.5 % higher stretch than untreated samples . the pore size distributions of papers were evaluated with simons stain procedure and experimental results usually consisted with sorption data . the less intense ch2ch2 - vibrations ( 14501700 cm1 ) and c - c and c - o - c peak areas in ftir spectra indicates lowering h - bonds in solvent treated and dried paper network structure .
***task***
the task is to summarize an input biomedical literature in six sentences

***input***
the input is a biomedical literature

***output***
the output is the summary of an input biomedical literature in six sentences

***documentation***

***examples***

input: a paper based product typically contains 9099 % cellulose fibers which are the primary structural element and the most important component influencing end use properties . a network of self - bonding cellulose fibers within network structure affects chemical and physical characteristics of the paper products . however , the chemical structure of cellulose is now well established and consists - anhydroglucose units with dominant hydroxyl groups , which are appropriate groups for reactions . these are mainly due to the one primary and two secondary hydroxyl groups in each monomer unit in polymer structure . each of anhydroglucose units are linked together by -1 - 4 glycosidic bonds . due to specific chemical arrangements of cellulose , it is completely linear homopolysacharide and has the ability to form extensive intra and intermolecular hydrogen bonds . because , paper network is composed from randomly laid fibrous ( cellulose ) and non - fibrous ( fillers ) materials , it contains a complicated set of cavity pore channels with a variety of capillary dimensions . however , the structure of paper can be modified during contact of liquids because it disrupts hydrogen bonds , relaxes fibers , and produces dimensional changes in pores and capillaries . if the effect of external pressure is neglected , the washburn equation could be used to describe the rate of capillary rise of fluids into paper . where dl / dt is the rate of penetration of the capillary , l is the distance penetrated into a cylindrical capillary of radius r , in time t , angle between liquid and surface , by a liquid with surface tension lv and viscosity . a number of studies have been conducted on the reasonably explanation for paper - liquid interactions . however , most studies have shown that the chemical and physical properties of fibers ( cellulose ) are reduced upon rewetting . consistently , the decrease of the absorption and strength properties of rewetted fibers because of changes in the basic structure during swelling and reducing fiber bonding potential . it was speculated that during drying , cellulose lose both free and bound water and start to shrink . it has modified to hard and stiff state ( hardening ) that have not reswell properly compare to never dried state . the mechanism of cellulose hardening is complicated and probably related with removal of bound water , lowers the distance between microfibrils and reducing the elasticity of fibrils . as a result of these modifications , the hydrogen bond cross - links could be formed between adjacent microfibrils in cellulose structure . the hydrophilic natures of the cellulose within paper structure are very important for good fiber - fiber bonding . however , the challenging aspects for wetting of papers understand how to increase and control fibers wetting and bonding . it is believed that repeating wetting and drying brings about irreversible changes in cellulose bonding potential . therefore , there is a need to understand more clearly the changes that take place in the rewetted cellulose fibers . these may open the possibility to increase recycling of cellulose based products ( e.g. paper and paperboards ) . moreover , new modified processes , involve various type of organosolv pulping approaches can also be required more detailed information on the effect of solvent systems on cell wall chemical constituents especially on cellulose . the objective of this study is to investigate the influence of various solvent formulations over repeating drying and wetting paper , composed only cellulose , in terms of evaluating chemical and physical properties . the experiments were conducted to ascertain the effect of various solvent formulations on liquid absorption , chemical and strength properties as well as capillary pore structure of papers . whatman filter paper , composed only from cellulose fibers , has completely free of all additives and fillers , was utilized as paper source under laboratory conditions . the whatman filter papers ( no : 1 ) and the chemicals with a purity of 9799 % , used in this study were purchased from yildiz kimya ltd ( ankara - turkey ) and utilized as received . the solvent treatments are designed to evaluate liquid sorption capacity through chemical modification and pore size distribution in paper network after continuously repeating drying and wetting cycles . four different solvents and their appropriate proportion mixtures were utilized in treatments : water ( h2o ) , ethanol ( etoh ) , methanol ( meoh ) , sodium hydroxide ( naoh ) . the constituents of solvent mixtures that paper samples treated at atmospheric conditions are presented in table 1 . five repeating wetting - drying stages were carried out to evaluate some chemical and physical paper properties . the sheets were soaked in the solvents at the atmospheric conditions for 8 hours . at the end of each wetting stage , the sorption properties of the samples were determined in conformity with tappi test method t 441 . but longer time was used to calculate liquid sorption as well as strength properties of samples . the tensile strength and stretch propertiesthis technique was based on the differences between the two type dyes ( direct blue i and fast orange 15 ) molecular size and affinity for cellulose . the dyes were purchased from pylam products co. , inc . , tepme , az , under the commercial names of pontamine fast sky blue 6bx and pontamine fast orange 6rn , respectively . the dyes were used as received , without further purification . the 1 g orange and blue dyewere dissolved in 100 ml distilled water then the dye solutions mixed in a ratio of 1:1 by volume . the small samples ( 1x1 cm ) were first soaked in dye solutions for 1 min and then 1 min in water . after that , they were put on a slide and dried at 75c , examined under a light microscope . direct blue i has a defined chemical structure with a molecular diameter of 1 nm . fast orange 15 dye is a condensation product of 5 - nitro - o - toluenesulfonic acid in aqueous alkali solution and its formula and structure are not well defined . however , it was proposed that the purified fast orange 15 dye has a molecular diameter in the range of 536 nm , which is much larger than the direct blue i molecular size . a shimadzu ir prestige - 21 series ir spectrophotometer was used to evaluate the chemical groups on the untreated and solvent treated papers . figure 1 shows liquid sorption properties of papers which are treated in water ( a ) , ( anhydrous ) ethanol ( b ) , ( anhydrous ) methanol ( c ) , 1 n sodium hydroxide ( d ) , up to five repeating drying and wetting stages . it can be revealed that the highest sorption occured with sample d ( 230.5 % in 1 cycle and 179.8 % in 5 cycle ) followed by sample a ( 182.3 % in 1 cycle and 170.6 % in 5 cycle ) , sample b ( 109.4 % in 1 cycle and 97.6 % in 5 cycle ) , and sample c ( 101.5 % in 1 cycle and 84.3 % in 5 cycle ) , respectively . this is not surprising because a number of researchers have already reported a definite correlation between chemical treatments and sorption properties for cellulosic materials . these reductions can be attributed to a change in the fiber polymer structure , such as hydrogen bonds cross - links or the elimination of h - bonding sites for liquids . because , all the liquids used in this study have hydrogen bonding ability and can penetrate into the paper network structure , followed by substitution of - oh for cellulose to cellulose hydrogen bonds . moreover , the closure of larger pores which do not reopen upon rewetting can be affects of high surface tension forces . this subsequent strain - hardening mechanism and forces may be welded the pores and resist against liquid penetration some degree . these are in good agreement with the results reported by wistara ( 1999 ) that dried fibers with higher initial swelling capacity have lower capability to reswell . however , 1 n sodium hydroxide treated sample ( d ) has considerably higher absorption value than others . after 5 repeating wetting - drying cycle , the sample d shows approximately 6 % higher absorption from sample a , 85 % from sample b and 114 % from sample c , respectively ( figure 1 ) . it can be attributed to reorientation of microfibrils and a better alignment of cellulose chains in sheet network structure that promote additional h - bonding sites for liquid . das and chakraborty ( 2006 ) was found that during alkali treatment , a lattice transformation from cellulose - i to cellulose - ii took place and sodium hydroxide introduces considerable changes in crystallinity and orientation angle within cellulose structure . these can be affects less crystalline region in cellulose hence further h - bonding place for liquids . the marked effect of sodium hydroxide addition to ethanol ( b ) in terms of sorption of paper ( e , f , and g ) is clearly evident in figure 2 . the highest absorption was obtained with sample f ( etoh - naoh 1:3 by vol ) after 1 wetting - drying cycle ( 185.7 % ) and further treatments decresing affects on liquid sorption of papers but they are still considerably higher than only etoh and lower amount naoh including systems . sample f showed approximately 4070 % higher liquid absorption compare to sample b ( 109.4 % ) at similar wetting - drying stages ( figure 2 ) . it seemed as if the increase of the liquid absorption was closely related to naoh content in etoh system and inversely related to wetting - drying stage . the sorption properties of papers at proportional mixture of methanol and sodium hydroxide reaction conditions are shown in figure 3 . similar to ethanol - alkali system , the highest absorption of 162.3 % was also found with sample i ( meoh - naoh 1:3 by vol ) but after 5 wetting - drying stage . one may also observe that extended drying - wetting usually affects 210 % increased liquid absorption properties for sample i. however , it can be realized that the liquid absorption was positively correlated with sodium hydroxide content in methanol system . these comparisons between the treatments and the measured results reveal that the sodium hydroxide response of cellulose can be predicted quite well by proportional mixture with ethanol ( figure 2 ) and methanol ( figure 3 ) . it was reported by rowell that the interaction between cellulosics and organic liquids was mainly influenced by the solvent ph , the molar size , and the hydrogen bonding capacity of the liquid . however , the variable sorption properties of sheets that treated with mixtures of ethanol and methanol with alkali , at similar conditions clearly reveals that the liquid absorption into paper sheet structure closely related to nature of the liquid ( ph ) and its surface tension as revealed in figures 13 . moreover , it has already proposed that swelling and sorption properties of papers in alkali conditions were higher than acidic conditions . this is probably related to fibril openings , which is influences the swelling capacity of cellulose , is an important factor to improve absorption potential of the fibers . watanabe and his group speculated that approximately 37 wt % of adsorbed water was responsible for the stabilization of the h - bond network at the cellulose - water surface . but , all the solvent systems used in this study have hydrogen bonding potential and they can penetrate into the web structure , followed by substitution of - oh for cellulose to cellulose hydrogen bonds . hence , inter and intrachain h - bonds of cellulose can be formed by solvent molecules during absorption . tensile strength of papers have usually used as an indication of the treatment affects on the paper strength derived from factors such as fiber strength , and bonding . the comparative tensile strengths of ten different solvent ( a - j ) treated papers with comparison to control that have strength of 37.3 n / mm are shown in figure 4 . all treatment conditions apparently bring about an effect of decreased strength for papers . after 1 wetting - drying stage , the highest strength loss was observed with sample a ( 16.8 n / mm , 54.9 % ) followed by sample b ( 18.0 n / mm , 51.3 % ) , sample f ( 18.6 n / mm , 50 % ) , respectively . however , the lowest strength found with sample b and d ( 13.0 n / mm , 65 % ) after 5 repeating wetting - drying stage . it is apparent that the treatment conditions were too severe , thus the strength properties of the papers sharply decreased . moreover , the addition of alkali to both ethanol and methanol ( e - j ) seems to have less affect on strength loss on papers . the porous structure of the sheets has a major influence on the penetration of a liquid into network . when paper contact with liquids , they tend to move from large cavities into smaller ones according to their different capillary pressures . it was proposed by atalla that the dehydration process of cellulose promote molecular mobility could result in enhancing levels of molecular organization . however , this molecular organization limits the capacity of fibers to respond to stress in an elastic mode without failure . the strength results found for cellulose paper in this study consisted with this information . when evaluating the tensile strength , also the stretch of paper at break ( elongation % ) should be considered . it is indicative of the ability of paper to conform to a desired property under nonuniform tensile stress . the comparative stretch ( as reported , elongation at break % ) of samples ( a - j ) are shown in figure 5 . it appears that repeated wetting - drying some level affects stretch in either increase and of decrease depends on solvent type and treatment stage . this is somewhat surprising , considering that the strength properties are considerably decreased with all treatments conditions . after 1 wetting - drying stage , the highest stretch improvement was found with sample g ( 26.8 % ) followed by with sample a ( 13.2 % ) , and marginally similar stretch improvements with samples b , c , h , i and j ( 48 % ) , in that order . however , after 5 wetting - drying stage , some papers shows considerably higher stretch than untreated and and / or lower treated samples . the highest stretch , hence , improvement was observed with sample e ( 59.5 % ) followed by sample i ( 49.8 % ) , sample j ( 28.7 % ) , sample h ( 21 % ) , respectively . moreover , samples b , c , d and f show approximately 1827 % stretch loss compare to control . the strength developments as well as physical behavior of papers are very complicated and depend on many factors such as structure of cellulose especially on crystalline region , and h - bonding of randomly laid network elements . but in brief , it is apparent that the strength properties of sheets considerably decrease with liquid treatments especially in acidic environment ( b and c ) but the addition of alkali ( naoh ) to both ethanol and methanol solvents seems to have less effect on strength loss , even some level improvement on stretch of papers realized in various conditions . simons stain is a practical technique for evaluating the pore structure of cellulose fibers , especially in recycling and pulping processes . when a mixture of two dyes ( direct blue i and fast orange 15 ) is applied to fibers , the blue and / or orange dye can absorbs to fibers with depending pore size . for fibers with a various pore size distribution range , the color of the stained fiber can depend on the ratio of surface area accessible to both dyes . the chemical structures of both dyes are shown in figure 6 . table 2 shows a summary of the paper samples obtained from various conditions and their staining properties under light microscope . it is realized that papers obtained from different conditions showed variable intensities of blue and orange stain . however , this rating does not reflect any quantitative measurements and that the comparison should to be made only within each experimental set . after 1 wetting - drying stage , except sample b , other single solvent treated samples ( a , c , d ) shows intensive light blue - orange color . moreover , paper samples that treated with proportional mixtures of etoh , meoh and naoh ( e - j ) have various level intermediate orange to dark orange color . this is clear evidence that alkali addition to acidic condition effects on increase pore size of fibers . because direct blue i has a smaller molecular size ( approx . 1 nm ) and a weaker affinity for cellulose compared to direct orange 15 , which has a larger molecular size ( 536 nm ) and a stronger affinity . but after 5 wetting - drying stage , most of the samples stained dark blue to light blue - orange color with the exception of sample f ( etoh - naoh , 1:3 by vol ) which the fibers stains intermediate orange and slightly dark orange . this is clear evidence that increasing alkali concentration in acidic solvents may be effects restoration of fiber pore size and effects less damaging with continuous drying and wetting . it has already stated above that , direct orange 15 molecules can preferentially be adsorbed on the fiber surface where the pore size is appropriate ( e.g. 5 nm ) for accessing direct orange 15 molecules . for the small capillary pores ( e.g. 5 nm ) , where the direct orange 15 molecules are not accessible , the direct blue i molecules can be adsorbed . therefore , the ratio of adsorbed direct orange 15 to adsorbed direct blue i is anticipated to serve as an indicator of the pore structure , specifically , the pore size population distribution of the paper . simons stain results are usually correlated with strength and sorption properties of papers ( figures 15 ) . the ftir spectra of various level solvent treated paper samples were obtained in range of 4004000 cm . however , the characteristic spectrum of cellulose structure concentrate in the range of 8002000 cm and the major peaks in this range had been identified . the comparative ftir spectra of various solvent treated papers after 5 repeating drying - wetting stage are shown in figure 7 ( a g ) . all spectra exhibit multi - modal absorption in the 6001000 cm region due to oh groups in cellulose . the out - of - plane c - h vibration was assigned at 750 cm . the band at 9001150 cm is attributed to c - c out of the plane stretching , c - c - o stretching at 1060 cm ; c - o - c symmetric stretching 1150 cm ( figure 7a ) . however , the spectra of solvent treated samples ( figure 7d f ) , exhibit the more absorption in the 8001200 cm region relative to the untreated cellulose , where a more complex in - plane oh vibration is dominant . however , the less intense ch2ch2 - vibrations ( 14501700 cm ) and c - c and c - o - c peak areas ( figure 7c , d , g ) indicates the generation of new surface chemistry which is related to the solvent induced / dried chain modification . young ( 1994 ) and weise and paulapuro ( 1996 ) found that drying affects lowering distance between microfibrils and cross - links in cellulose structure . the result found with ftir evaluation of cellulose sheets that treated with various solvents and continuously wetted - dried cycles , support this information . on the basis of ftir measurementsit was concluded that some modification had taken place during solvent diffusion and solvent induced chain modification occurred in cellulose structure . a number of solvent treatment conditions were utilized for evaluating cellulose paper in terms of liquid absorption , strength as well as sheet network structure of papers . it can be revealed that repeating drying and wetting usually affects on decreasing liquid absorption and strength of cellulose papers . these can be attributed to a change in the fiber polymer structure especially elimination of h - bonding sites for liquids . however , liquid absorption was significantly improved by alkali addition to both meoh and etoh solvent systems . ftir measurements indicated some modification had taken place during solvent diffusion and solvent induced chain modification occurred in cellulose structure .
output:
