Study On Preparation And Properties Of Composites From Poly (Lactic Acid) And Cellulose Nanocrystals Containing Different Groups

Poly(lactic acid)(PLA)due to the advantages of wide sources of the raw materials,nontoxicity and good biocompatibility has been favored by the researchers,but the low crystallization rate and low crystallinity of PLA limit its application.Cellulose nanocrystals(CNC)have attracted a great deal of interest in the nanocomposites field due to their appealing intrinsic properties including nanoscale dimensions,high surface area,unique morphology,low density,and mechanical strength,as well as the fact that they are readily available,renewable and biodegradable.Different kinds of CNC are produced by acid hydrolysis,oxidizers and Surface acetylation.Then the mechanical properties,thermodynamic behavior and crystallization behavior of the composites are explored.The crystallization properties of the composites are further studied by adding CNC in the PLA/PBS system.The results showes that,with the addition of 3 wt% CNC,the crystallinity degree of nanocomposites are increased to 47.5% and the tensile strength of the PLA/CNC nanocomposites are enhanced by 10%.The spherulitic morphology study reveales that CNC act as an efficient nucleating agent for the crystallization of PLA,as the spherulites size become significantly smaller with the addition of CNC and the crystallization rate is increased.The crystallization behaviors of miscible poly(butylene succinate)/ Poly(lactic acid)(PBS/PLA)and its blend composites with cellulose nanocrystals(CNC)during non-isothermal and isothermal processes are investigated.The results showes that CNC act as heterogeneous nucleation agents and further improve the nucleation ability of PBS and PLA respectively.However,crystallization peak of PLA around 116? disappears in PBS/PLA/CNC ternary composites,which means the crystallization of PLA is largely restricted.A reasonable explanation about the restricted crystallization of PLA is studied from the viewpoint of interfacial interactions between polymer components and CNC,in which a preferential affinity of CNC to PBS is found.