Preparation And Characterization Of The Grafted Copolymer Of Acrylic-Starch/PLA Blends

Starch/Poly-Lactic-Acid(PLA) Compsite,as a kind of new totally biodegradable plastic with a bright foreground,take a balance between the high performance of Poly-Lactic-Acid and the inexpensive of starch.This compesite can not only economize petroleum resources,but also develope a new nonfood use of starch.In this study,Poly-Lactic-Acid(PLA) was synthesized by direct polycondensation,then the molecular weight of PLA was further enhanced by the way of solid-phase homopolymerization;Starch-g-poly(Crylic acid) was prepared by the the method of grafting;then the grafted copolymer of acrylic-starch/PLA blends were produced by graft copoly merization-blending.The changes of the mechanical properties,thermal performance,hydrophilicity as well as the degradation of performance of starch -g-p/Poly-Lactic-Acid(PLA) composite was studied by the tensile strength test,infrared spectroscopy,X ray diffraction,DSC and SEM analysis.The results were that:1.The result of single factor test and orthogonal test showed that the optimum conditions of direct synthesis of poly-lactic-acid were as follow:reaction temperature 170℃,reaction time 11h,the quantity of SnCl₂ added 0.5%,the amount of toluenesulfamides acid was 0.3%;At this time the molecular weight of PLA was 11,655;Yield of PLA was about 88.06%.2.The ultimate molecular weight was about 21,100 after the way of solid-phase homopolymerization.The results of infrared testing and degradation of performance test showed that the sample was poly-lactic-acid which had best performance of degradation;the final product yield of PLA can be 80.09%.3.the optimised synthetic conditions of grafting acrylic acid(AA) onto corn starch result from the orthogonal experiment were that St/AA=1/1,reaction time is 1.5 hours and the reaction temperature is 80℃,the amount of CAN is 11mmol/L. At that time,grafting ratio,grafting efficiency,monomer conversion ratio is 167.4%, 94.71%and 98.90%in respective.It was found that crystallinity decreased while water absorption increased after the starch is grafted with crylic acid.The result of fourier transform infrared spectroscopy(FTIR) check showed that acrylic acid have grafted into the base of starch successfully.4.The best blending conditions of Starch-g-poly(Crylic acid)/PLA were that the adding amount of modified starch was 30%,blending temperature was 80℃,the best blending solvent was DMSO.Compared with the pure starch/PLA blends,it was found that the tensile strength test and the hydrophilic of the Grafted copolymer of Starch-g-poly(Crylic acid)/PLA blends increased while crystallinity decreased,the SEM pictures showed that the compatibility of strach and PLA greatly increased while the starch grafted with acrylic,and the speed of degradation decreased slightly.