Preparation And Properties Of Biodegradable Polyvinyl Alcohol Composites

Biodegradable materials have excellent biocompatibility and physical-chemicalproperties. It has been extensively applied in the packaging, agriculture andbiomedical fields. Recently, because of the special requirements of water resistanceability, the development of films has a new research direction. Poly (vinyl alcohol)are hydrophilic and biodegradable polylmer which mainly exists the strongintermolecular hydrogen bonding, high crystallinity, difficult to thermoforming;However, its water absorption is related to its degree of hydrolysis, molecular weightand the modification while blending with other processing additives. The mainshortcomings of biodegradable film are hydrophilicity and poor mechanicalproperties.This thesis has done the reaseach on biodegradable materials to overcome themain shortcomings. At the same time, the influence of adding accessory ingredient,such as glycer in agent on the flims has been studied.This thesis by dialdehyde starch(DAS), poly (vinyl alcohol)(PVA), sodium carboxymethyl cellulose (CMC), chitosan(CS), palygorskites clay (PGS) as raw material, we preparation three types ofbiodegradable materials are DAS/PVA composites, PVA/CMC/PGS composites andPVA/CS/PGS composites. The structure and feature of the composites wascharacterized by Fourier transform infrared spectrogram (FTIR), scanning electronmicroscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA),mechanical tension, water resistance, biodegradability.(1) In this work, corn starch was oxidized under mild conditions using sodiumperiodate to prepare dialdehyde starch (DAS) with an acceptable average molecularweight. DAS-poly(vinyl alcohol)(PVA) full biodegradable composites reinforced withjute strands were obtained by flow casting method. The results showed that jutestrands could promote the compatibility of matrix PVA and DAS, because of thesurface hydroxyl groups of jute strands. Due to the water resistant of jute strands, thenewly prepared composite’s water absorbability could be reduced greatly,biodegradability also could be improved. The composites demonstrated lower waterabsorption, and better mechanical properties and biodegradability when the content ofPVA, plasticizer glycerol, jute strands was8%(w/w),30%(w/w) and6%(w/w)(for the quality of DAS) respectively. The highest tensile strength and elongation at breakreached28.7MPa and31.4%, respectively, and the highest water absorption wasabout16.8%. After30days of out door soil burial in summer, the weight loss wasalmost90%.(2) Poly(vinyl alcohol)/sodium carboxymethyl cellulose/palygorskites claynanocomposites were prepared by a solution mixing method. The effects of the massratio of sodium carboxymethyl cellulose to poly(vinyl alcohol), palygorskites content,the mass fraction of plasticizer, and the pH value of solution on the properties ofnanocomposite were investigated. The structure of the samples was characterized byX-ray diffraction, scanning electron microscope. The thermal property was measuredby thermogravimetric analysis.The results show that the compatibility of the blendfilms is good, and the comprehensive mechanical properties are improved comparedwith those of single component. The water resisting property and mechanical propertyof CMC/PVA/PGS blend film increased remarkably by adding the treated PGS. Thetensile strength was9.9MPa, elongation at break was320.9%, when the amount ofPGS was3%, crosslinking agent was6%, pH was5respectively. Under the RH=68%conditions, water absorption is10.5%.The results show that the mechanicalproperties of the PVA/CMC/PGS compared to the PVA/CMC composite materialcould be improved, the main reason is that one-dimensional nanofiber PGS is of verygood filling composite materials and the matrix combining closely, and realize thenanoscale disperse.(3) A type of hybrid membrane was prepared by using polyvinyl alcohol (PVA),chitosan (CS) and palygorskites (PGS). The comprehensive mechanical properties areimproved.The tensile strength was26.4MPa, elongation at break was335.3%, whenthe mass ratio of PVA to CS was9:1, the amount of PGS was3%(the total weight ofPVA and CS), the quality of plasticizer glycerin concentration was0.25wt%, aceticacid concentration was3%respectively. Through the X-ray diffraction(XRD) andscanning electron microscopy (SEM) microscopic structure analysis show that PVAand CS has a good compatibility, no obvious phase separation.When addindpalygorskites, it can be cooperated with the free hydroxyl of PVA and CS forminghydrogen bond, and formed the specific density homogeneous structure. The preparation of the composite material for the soil burial degradation,microbial degradation of the test, and the results show that: the compound membranehas good biological degradation properties. In biodegradable plastic industry,especially in the field of disposable packing material have broad applicationprospects.