Study On The Application Of Lignophenols In Composite Films And Water-absorbent Resin

With the continuous development of technology and the continuous improvement of human's cultural quality,environment and resource issues have been hot issues for scholars.Under the current situation,the development and utilization of renewable resources has become the focus of research.Lignin,as the second most abundant renewable biopolymer in nature,its application was limited by its complex and irregular structure.It is usually used as waste combustion for energy in pulping and papering process.In this paper,in order to comprehensive application of lignin,lignophenols,owned more active groups and more regular structure,were prepared by phase separation system.Then lignophenols were used to synthesized composite films and water-absorbent resins.And the effects of lignophenols on the properties of composite films and water-absorbent resins were studied.The contents and results are as follows.On the one hand,lignophenols were mixed with biodegradable plastics by solvent blending to cast thin composite films.Bamboo lignophenols,including lignocresol,lignocatechol,lignoresorcinol and lignopyrogallol,were blended with polyhydroxybutyrate?PHB?in chloroform at 90 °C by physical blending method to cast thin biocomposite films and their mechanical and thermal properties were tested and discussed.The results showed that the overall performance of the composite film was the best when the lignocresol content was 3 wt%.Under the same process conditions,compared with other lignophenols,lignoresorcinol was most favorable filler for the lignophenol-PHB composite films.Since polypropylene?PP?fiber possessed good strengthening and toughening features and was often filled into reinforced concrete to improve its mechanical performance,it was added to lignocresol-PHB composite films,and the effects of PP fiber and lignocresol on mechanical and thermal properties of composite films were studied.Otherwise,the crystallinities and degradation properties of composite films were also measured.The results show that PP fiber had little effect on the mechanical properties of the composite film,but the thermal stability of the composite film was decreased.And PP fiber was difficult to degrade,while the addition of lignocresol had no effect on the degradation of PHB.Poplar lignophenols,including lignocresol,lignocatechol,lignoresorcinol and lignopyrogallol,were blended with polylactic acid?PLA?in chloroform at 90 °C by physical blending method to cast thin biocomposite films.The effect of lignocresol content and lignophenols species on the mechanical and thermal properties of composite films were tested and discussed.The results showed that adding lignocresol into PLA-based films had a negative effect on mechanical properties of composite films.When lignocresol content was 15 wt%,the thermal stability was the best.Under the same conditions,compared to other lignophenols,lignocatechol-PLA composite films showed the best properties.In order to improve the compatibility between lignocresol and PLA,lignocresol was modified by grafting with methacryloyl chloride.The grafted products were characterized by1H-NMR,fourier transform infrared spectroscopy?FTIR?,ultraviolet spectrophotometry?UV?,and gel permeation chromatograph?GPC?analysis.And then the modified lignocresol was were blended with PLA in chloroform at 90 °C by physical blending method to cast thin biocomposite films.The effect of modified lignocresol content on the mechanical and thermal properties of composite films were tested and discussed.Otherwise,the crystallinities of PLA-based films were tested by X-ray diffraction?XRD?analysis.The results showed that when the modified products were grafted by methacryloyl chloride for four times,the the content of phenolic hydroxyl of modified products stabilized.GPC analysis showed that the molecular weight of the modified products significantly increased,while the characteristic absorption peak of modified lignocresol were also found on FTIR and 1H-NMR spectra.These data proved the success of grafting.And the composite films showed best properties when the adding content of modified product wass 10 wt%.On the other hand,lignin including alkali lignin?AL?,lignosulfonate?LS?,lignocresol?LC?,lignoresorcinol?LR?and lignopyrogallol?LP?were grafted by acrylic acid?AA?to synthesized water-absorbent resin under aqueous solution with potassium persulfate?KPS?as initiator and N'N-methylene-bis-acrylamide?MBA?as crosslinking agent.The optimum process of lignosulfonate-grafted-polyacrylic acid resin?LS-PAA?were discussed by using the single-factor method.The results showed that when monomer concentration was 30%,the dosage of lignosulfonate was 2.67 wt%?to AA,the same below?,dosage of crosslinking agent was 0.03 wt%,dosage of initiator was 0.43 wt%,neutralization degree was 65%,and the reaction temperature was 60 °C,water absorption capacity of lignosulfonate-grafted-polyacrylic acid resin?LS-PAA?was highest?1348 g/g?.Otherwise,the effects of lignin species on the properties of resins were discussed under the above conditions.The lignins were characterized by 2D-NMR and the resins were characterized by field emission scanning electron microscopy?FE-SEM?and BET specific surface area analysis.The swelling behaviors of the resins were fitted by the swelling kinetics model.The results indicated that water absorption capacity of resins varied with lignin species: LP-PAA resin?2137 g/g?> LS-PAA resin?1348 g/g?? LR-PAA resin?1344 g/g?> LC-PAA resin?1262g/g?>> AL-PAA resin?518 g/g?> polyacrylic acid resin?PAA??439 g/g?.The porosity and BET specific surface area showed a comparable trend.And the swelling behaviors of the resins were proved to according with Schott swelling kinetics model.Salt tolerance of LP-PAA resin were studied and the results were as follows: KCl > KNO₃ ? LiCl > K₂SO₄ > K₂CO₃ >CaCl₂ >FeCl₃.