Preparation And Properties Of Hydrophobic Modified Polysaccharide/protein/PVA Composite Plastics

Plastics play an important role in modern human life and food packaging.However,the slow degradation of traditional plastics has brought great pressure to the environment,so research on biodegradable plastics has emerged.Pure polyvinyl alcohol plastic has poor mechanical properties and low degradation rate,which limits its application.While biomacromolecules have the advantage of being degradable but their hydrophilicity is greater.Therefore,biological macromolecules were hydrophobically modified and then blended with polyvinyl alcohol and protein to further expand the application of degradable plastics.In this paper,potato starch,mung bean starch,chitosan and konjac glucomannan were synthesized by octenyl succinic acid esterification,acetic anhydride esterification,crosslinking and deacetylation,respectively,and then mixed with soybean protein,zein and polyvinyl alcohol.The ratio of polysaccharide to protein was 0:4、1: 3,1: 1、3: 1 and 4: 0,and the substitution ratio of polysaccharide protein to polyvinyl alcohol was 25%,50% and75%.The structural,physicochemical and functional characteristics of composite plastics with different proportions were compared and studied,and further explore the contribution of modified polysaccharides,proteins and polyvinyl alcohol to physical,chemical and functional characteristics of composite plastics,then explore the interaction mechanism of the internal structure of composite plastics.The main conclusions are as follows:(1)Compared with pure PVA plastic,the composite plastic has a small amount of incompatible particles floating outside the continuous components.When the ratio of OSA starch to gladin was 1: 1,and the ratio of replacing polyvinyl alcohol was 25%,the surface components of the composite plastic had the best compatibility.When the replacement rate increased to 75%,the composite plastics had the lowest water absorption.When the replacement of PVA reaches 50%,the mechanical properties of the composite plastic were the best.In addition,the biodegradation rate of plastic was improved by adding OSA starch and glutenin.(2)The surface of the composite plastic prepared from acetic anhydride esterified mung bean starch,gliadin and PVA has a uniform and flat morphological structure,and the roughness value is lower than that of pure PVA plastic.The composite plastics was lower than that of pure PVA plastics.When the replacement rate increased to 75%,the composite plastics had the lowest water absorption.When the overall replacement rate of acetic anhydride esterified starch and gliadin was 50%,the tensile strength of composite plastics reached the maximum.The biodegradation rate of plastics can be significantly improved by adding acetic anhydride esterified mung bean starch and gladin.(3)When the ratio of crosslinked chitosan to soybean protein was 1: 1 and 1: 3,and the substitution rate of PVA was 50% and 75%,the surface of composite plastic was smooth.The water absorption and water vapor transmission rate of the composite plastic were all lower than that of pure PVA plastic,and the water absorption rate of composite plastics gradually decreased with the increase of the replacement rate of cross-linked chitosan and soybean protein.As the ratio of cross-linked chitosan to soy protein increased,the tensile strength of the composite plastic gradually increased,while the elastic modulus gradually decreased.By adding crosslinked chitosan and soybean protein to the plastic,the biodegradation rate of the plastic can be increased.There were many holes and cracks on the surface of the composite plastics after burial,and mixed plastic degraded rapidly in the first three weeks,and then the degradation rate slowed down.(4)The surface of the composite plastic prepared from konjac glucomannan,zein and PVA had phase separation.When the ratio of deacetylated konjac glucomannan to zein was9:1,the compatibility of the three components was the best.The composite plastic formed by the deacetylation of konjac glucomannan has lower L* and higher a*,b*,c* and ΔE values than the original konjac glucomannan composite plastic.Compared with pure PVA plastics,composite plastics have lower water absorption,water vapor transmission coefficient and tensile strength,as well as higher elastic modulus and thermal properties.By adding konjac glucomannan and zein to the plastic,the biodegradability of the plastic can be improved.The composite plastic prepared by hydrophobically modified polysaccharide,protein and PVA had a smooth and flat surface,and had a significant improvement effect in physicochemical and functional properties.As a food packaging material,the composite plastic had lower water sensitivity,higher thermal characteristics,and significantly improved biodegradability.As biodegradable materials,polysaccharides,proteins and polyvinyl alcohol could provide more choices and possibilities for food packaging materials due to their unique physicochemical and functional properties.This study will provide basic data and theoretical basis for the preparation and research of biodegradable food packaging materials in the future.