Research On New Catalytic Systems Of St-g-PLA Copolymer And Composite Film Of It

Biodegradable polymer materials are one of reasearch hotspots in polymermaterial field, so the study on lactic acid grafting starch copolymer has beenreceived much attention in recent years. The starch modified with lactic acid, whichis biodegradable and renewable resources, and prepared composite materials have acertain practical significance and potential applicable prospect.In this work, the in-stiu copolymerization of starch graft with lactic acidcatalyzed with general chemical reagents has been studied, the structure and propertyof starch/lactic acid graft copolymer（St-g-PLA） are characterized by modern analysistechnology means, and the performances of composite films of St-g-PLA copolymerare also studied simply. And the detailed studies are showed as follows:Systematical studies have been made on the in-stiu graft copolymerization ofstarch and lactic acid catalyzed with common chemical reagents （such as NaOH,ZnO and SnCl₂） by one-step, and the structure of St-g-PLA copolymer ischaracterized by IR、NMR、XRD、SEM as well as other test analysis method. Theexperimental results show NaOH, ZnO and SnCl₂all can catalyze the graftcopolymerization of starch with lactic acid to prepare St-g-PLA graft copolymersuccessfully, while the quantitative measurement of the grafting degree of starchshows the catalytic effect of NaOH is more effective than ZnO and SnCl₂with thestarch grafting degree up to33.60％under the current condition. The thermalresistance of St-g-PLA copolymer has little declined compared with cornstarch, andthe glass transition temperature decreased with the increasement of the starchgrafting degree. And the solubility property of St-g-PLA copolymer has beenimproved to starch in ordinary organic solvents such as ethanol, but insolubility inwater.To study the application feasibility of St-g-PLA copolymer, a pilot reaearch ismade on the film technology and performance of the St-g-PLA copolymer. Thecomposite film was made of St-g-PLA and PVA mainly, and the effects ofSt-g-PLA/PVA composite film of the ratio of raw materials、kinds and dosage of cross-linking agent and plasticizer and film technological conditions are discussed,then tensile strength, elongation at break and other properties are testedquantificationally. Results show St-g-PLA/PVA composite film can be prepared withglutaraldehyde as cross-linking agent and glycerol as plasticizer, and the tensilestrength of St-g-PLA/PVA film can reach19.96MPa as well as breaking elongationrate up to208.35％and water absorption at70.59％with3:5as the mass ratiobetween St-g-PLA and PVA,1.5％as amount of glutaraldehyde,10％as amount ofglycerol at85℃for25min, whose comprehensive properties are superior to St/PVAfilm obviously. While the research result of thermal performance showedSt-g-PLA/PVA film has better heat resistance than St/PVA and PVA films. The filmshows potential application prospect owing to its good environment degradationperformance.