Study On Preparation And Characterization Of Biodegradable PLA-Based Nanocomposites

The exploration and application of degradable polymer have become one of the most effective solutions for petroleum-based plastic waste problem. Thereinto, poly(lactic acid)(PLA) have many merits such as excellent biodegradability, processability, simple manufacture flow and have become the main product among degradable polymers. Aimed at the problems of the application of PLA such as: low toughing(belongting to brittle fracture), dispropotion between strength and toughing, PLA with high molecular weight difficult to biodegrade and so on, this paper is concentrated on the modification of PLA and the prepatation of PLA-based nano-composite,whose properties not only reach to the balance of strength and toughing, but also statisfy the utilization demand from the view of mechanical properties. Moreover, the sysmatic research is performed on the effect of components of PLA-based nano-composite on its mechanical properties, microstructure and biodegradability.PLA/modified organo-montmorillonite (PLA/OMMT) nanocomposite is prepared through melt-intercalation on the single-screw extrusion machine. La-OMMT is obtained through exterior treatment by rare earth oxide(La2O3), which improve the compatibility and interfacial binding between OMMT and PLA. PLA/La-OMMT nanocomposite is attained through melt-intercalation, and then is plastisized by plastisizer. The effect of the content of OMMT, the effect of the type of OMMT, the effect of the weight ratio of La2O3 and OMMT, the effect of the content of La-OMMT, the content of plastisizer and the type of plastisizer on the mechanical properties of PLA-based nanocomposite are investigated. The results conclude the suitable type of OMMT and plastisizer, moreover, their optimal content in PLA-based nanocomposite.The microstructure of PLA-based nanocomposite is studied through SEM,XRD and TEM, which provide direct intuitionistic interpretation for mechanical properties of PLA-based nanocomposite. Besides, the mechanism of enhancing strength and toughing of PLA-based nanocomposite is discussed. The results indicate that La-OMMT, which is mainly exfoliated in nanocomposite, play a role in enhancing strength, meanwhile, PEG improve the toughing of nanocomposite. The integration of strength and toughing broaden the field of the application of PLA.The biodegradable behavior and biodegradable mechanism of PLA-based nanocomposite with good mechanical properties are studied in this paper. Under the biodegradation of the microbe from activated sludge and soil cultivated liquor,respectively, the change of Weight loss, viscosity molecular weight of PLA-based nanocomposite versus time are studied, and the configuration before and after biodegradation are observed through SEM. Furthermore, the effect of the addition of nanoparticle La-OMMT and hydrophilic PEG on biodegradability of PLA-based nanocomposite are discussed, which show that this two component quiken the biodegradation of PLA-based nanocomposites.