Study On Preparation And Structure Characterization Of Organically Modified Montmorillonite And Poly (Lactic Acid)/Montmorillonite Nanocomposites

Polylactic acid(PLA) is a kind of linear-biodegradable aliphatic polyesters,which is synthesized artificially with lactic acid. Lactic acid are acquired through enzyme and lactobacillus action, whose original materials are starch from wheat,corn,cassava etc. PLA has an excellent performance of biodegradation and biocompatibility. The waste of PLA can finally be degraded into carbon dioxide and water under the function of microbe,light,water,acid and alkali in the nature. Then carbon dioxide and water turn into the raw material of starch due to the photosynthesis of sun, which never cause the pollution to environment. So the PLA is the completely natural-circular biodegradable polymer materials. The exploitation and studying of PLA have been drawing people s more attention in recent years, and the applications of PLA will be broader.First, the activated montmorillonite(MMT) was modified by toluene-2,4-diisocya-nate(TDI) and the TDI/MMT was prepared in this article. The effects of reaction conditions, such as reaction time,reaction temperature,TDI dosage and the activated condition of montmorillonite on the degree of TDI reaction were discussed by the method of single factor experiment. The optimum modified conditions as follows:reaction temperature 80℃,the mass ratio of montmorillonite to toluene-2,4-diisocyanate 1:0.3, and the degree of TDI reaction could reach 34.28%. Second, consulting the method of TDI modifying montmorillonite, MDI/MMT was also prepared. Besides, the modification product was characterized by IR,XRD and TG techniques. The results showed that:TDI reacted with the hydroxyl group of montmorillonite layers and the free-NCO group successfully remained on the surface of montmorillonite; the interlayer distance of modification product was increased further, consequently the organic montmorillonite(OMMT) was achieved. Finally, the PLA/OMMT nanocomposites were prepared through two steps in this experiment. Step 1, the lactide was obtained by using lactic acid as materials; Step 2, nanocomposites were got by ring-opening polymerization of lactide in the presence of TDI/MMT. The influence of quantity of TDI/MMT on property of nanocomposites was studied in this investigation, also, the structure and performance of nanocomposites were analyzed by IR,XRD and TG techniques. The results showed that:lactide was being ring-opening polymerization in the interlayer of MMT via in-situ polymerization; The heat was released by polymerization to overcome the coulomb force in the interlayer of MMT, which brought on the lactic to disperse in PLA averagely, they combined closely and PLA/OMMT nanocomposites were prepared. Comparing to the PLA, the decomposition temperature and thermalstability of nanocomposites were obviously improved.