Preparation And Properties Of Polyvinyl Alcohol-Based Antibacterial And Water-Resistant Film

Polyvinyl alcohol(PVA)is one of the few biodegradable synthetic resins,but because the structure contains a large number of hydroxyl groups that are easily soluble in water,it is necessary to improve the water resistance of PVA-based materials when they are used in humid environments.In addition,the demand for antimicrobial films has surged in the food packaging field,and it is especially important to select safe and compatible natural antimicrobial agents and inorganic nanobacterial agents.In this thesis,PVA was studied to prepare modified PVA films by chemical cross-linking with cinnamaldehyde(CIN)or vanillin(Van),blending with κ-carrageenan(KC)polymer,and filling with zinc oxide nanoparticles(ZnONPs)in a formulation using solution casting method.The study was divided into three parts:(1)Under the condition of p H=2 in the presence of citric acid(CA),PVA/CIN/CA films with CIN contents of 12.5%、25.0%、37.5% were prepared,and the best mechanical properties of PVA/CIN films were obtained when the CIN addition was 25.0%Accordingly,PVA/CIN/HCL films with CIN content of 1.0% and PVA/Van/CA films with Van content of 25.0% were prepared under hydrochloric acid(HCL)environment as a comparison.By infrared analysis(FTIR),thermogravimetric analysis(TGA),and X-ray diffraction(XRD)analysis,it was determined that hydroxyl aldehyde condensation reaction occurred between CIN,Van,and PVA under both CA and HCL acidic conditions;the hydroxyl aldehyde condensation reaction improved the water resistance of PVA films as demonstrated by moisture absorption,water vapor transmission coefficient,and water contact angle tests;meanwhile,by inhibition circle test,the films with CIN added In addition,the films with CIN,Van,and CIN-Van showed antibacterial properties through the inhibition circle test.(2)Prepared PVA/KC blended films with KC contents of 2.5%,5.0%,7.5%,10.0%,and 12.5%,and the best mechanical properties of PVA/KC blended films were obtained when the KC addition was 7.5%.Accordingly,PVA/KC cross-linked films were prepared by adding 25.0% Van as cross-linker in the presence of CA at p H=2.By FTIR analysis,TGA analysis,and XRD analysis,it was determined that only hydrogen bonding linkage was present in the PVA/KC cross-linked films,and hydroxyl aldol condensation reaction involving Van was present in the PVA/KC cross-linked films.The water resistance of both the blended and cross-linked films after blending was improved by moisture absorption,water vapor transmission coefficient,and water contact angle tests.The PVA/KC blended film did not have antimicrobial properties by the inhibition circle test,while the PVA/KC cross-linked film had antimicrobial properties.(3)Pure PVA films,PVA/CIN cross-linked films with a CIN content of 25.0%,PVA/Van cross-linked films with a Van content of 25.0%,PVA/KC co-blended films with a KC addition of 7.5%,and PVA/KC/Van cross-linked films with a Van content of 25.0%were each added with 5.0% of ZnONPs were prepared for the PVA/ZnONPs composite films and compared with each PVA film without the addition of ZnONPs.Microscopic analysis showed that the addition of ZnONPs did not produce chemical reactions;the mechanical properties and water resistance properties did not change much,but the antibacterial properties were further improved.This study modified PVA by CIN and Van cross-linking,KC co-blending,and ZnONPs filling,all of which effectively improved the mechanical properties and water resistance of PVA films,while CIN and Van as natural antimicrobial agents,non-toxic and non-hazardous inorganic antimicrobial ZnONPs also gave PVA films good antimicrobial properties,providing a theoretical basis for the application of PVA films,especially in the food packaging This provides a theoretical basis for the application of PVA films,especially in the field of food packaging.