Preaparation And Properties Of Starch/Poly(Lactic Acid) Composites

Poly(Lactic Acid)(PLA)is a kind of high performance biodegradable material. In comparision with other biodegradable materials, it has many advantages such as high strength, thermoplastic, hydrphobicity, good fabricability, biodegrability, availability from renewable resources and bioenvioronmental compatibility. But PLLA is too expensive, so the application of PLLA is usually limited in the biomedical area. Starch/Poly(Lactic Acid) composite , 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 composites can not only economize petroleum resources,but also develop a new nonfood use of starch。However,native starch is hard to be melted,so, generally,starch granule is hard to be melted and mixed homogeneously with Poly(Lactic Acid) in blends。That could lead to poor poor mechanical properties and limit the starch content of the blends。The blends of starch and poly(lactic acid) with different ratios were prepared in the rheometer , and their morphology mechanical properties were characteried. Results show that starch performed as fillers in the PLA continuous matrix phase wilh two phase separated according to SEM,and with the increase of starch content, mechanical properties decrease sharply.In order to imporve the compatbiliity between stacrh and PLA, different methods were tried to affect starch phase or interface. We made starch into crosslinked starch, it was find that strength of the blend increased with increasing starch crosslinking. Starch was plasticized by glycerol,then blended with PLA. Blends shows beter tensile strength,flexural strength and impact strenth, when the mass ratio of glycerin was 8%, composites had the best strength, breaking elongation was increased with the increase of glycerin. Free-radical-initiated grafting of maleic anhydride (MA) onto a polylactide(PLA) backbone was performed by reactive extrusion. The maleation of PLA proved to be very efficient in promoting strong interfacial adhesion with corn native starch in composites as obtained by melt blending, when the mass ratio of tert butylperoxy benzoate was 0.0625%, composites had the best strength. We added rubber to improve the tenacity of composites, it was find that when 5%(wt.) of rubber was filled into the blend, breaking elongation can improve 300%.