Preparation And Properties Of Polyvinyl Alcohol/soluble Starch Cling Film

Fully biodegradable materials are one of the current research hotspots for developing new composite materials in response to environmental problems,and also an effective way to achieve carbon peaking and carbon neutrality.Based on the excellent film-forming and biodegradable properties of polyvinyl alcohol and the cheap and renewable properties of starch,they have great potential for application in the field of film packaging.This thesis addresses the problems of insufficient mechanical properties,poor water resistance and low freshness of fully biodegradable polyvinyl alcohol/soluble starch cling film.Polyvinyl alcohol and soluble starch were used as substrates,d-sorbitol as a plasticizer,and citric acid as a cross-linking agent to produce a blended film with excellent mechanical properties;ethyl orthosilicate was added as the coupling agent and hydrochloric acid was used as a catalyst to silylate grafting of polyvinyl alcohol and microcrystalline cellulose to further improve the water-resistance of the film;fumed silica as carrier and glucose as reducing agent was also used to prepare the blended film.The silver-loaded silica was used as an antimicrobial agent to obtain a fully biodegradable cling film with high freshness retention.By characterizing the mechanical properties and structural morphology of the films,the effects of different additive contents,different microcrystalline cellulose grafting contents,and different silver-carrying silica contents on the water absorption,solubility,light transmittance,water vapor transmission rate,freshness,and degradability of the films were obtained.The results of the study showed that:(1)By testing the performance of the blended films,the optimal content of soluble starch addition was 10% to 30%,d-sorbitol addition was 10% to 20%,and citric acid addition was 5% to 15%;by orthogonal analysis,the ratio of polyvinyl alcohol to soluble starch was 82.83:17.17,d-sorbitol addition was 12.39%,and citric acid addition was 8.95%,The water vapor transmission rate of the prepared film did not meet the standard and the water resistance was poor.(2)Through the study of covalent bonding and crystallinity of the film,the best grafting effect was obtained when the ratio of microcrystalline cellulose to ethyl orthosilicate was 2:4;through the thermogravimetric analysis of the film,the thermal stability of the film was best when the content of microcrystalline cellulose was 2%;the water vapor transmission rate of the film grafted with 2%microcrystalline cellulose could be reduced by 27.37%,and the water absorption rate and solubility were reduced by 11.69% and 7.99%,respectively,which improved the water vapor transmission rate of the film.The water vapor transmission rate of the grafted 2% microcrystalline cellulose film was reduced by 27%,and the water absorption and solubility were reduced by 11.69% and 7.99%respectively,which improved the overall water resistance of the film and extended its performance as a cling film.(3)When the p H of the silver ammonia solution is 10,the highest silver loading of silver silica prepared is 6.9%,and the cling film with 0.05% silver-loading silica can improve the freshness of banana by 33.3% compared with polyethylene cling film,and the cling film can reach brittle degradation in about the twentieth week.It is a reliable whole biodegradable cling film.