Crystallization Behavior Research Of PLA/Sisal Composites

Transcrystallization behavior of PLA on sisal fiber, the compatibility of PLA/CAB and the influence of CAB to the crystallization of PLA, and crystallization behavior and properties of PLA/sisal composites was studied in this paper.In transcrystallization behavior of PLA on sisal fiber, there was three kinds of sisal fibers, and they were U-sisal(untreated), A-sisal(Alkali-treated) and S-sisal(silane-treated) respectively. DSC was used to measure the Tg (glass transition temperature) and TmO (equilibrium melting point) of PLA. The polarizing microscope was used to measure the nucleation and growth rate of PLA on sisal fiber. Heterogeneous nucleation theory was used to calculate the interface energy difference function, which represents the nucleating ability. It was demonstrated by experiment results that the nucleating ability of A-sisal and S-sisal were not improved, compared with U-sisal.In the study of the compatibility of PLA/CAB, DSC was used to measure Tg of PLA/CAB, non-isothermal crystallization behavior and TmO of different components. The polarizing microscope was used to observe isothermal crystallization morphology of all components at selected temperatures and molten state, and thus the growth rate of spherulites were calculated at all crystallization temperatures. Results showed that PLA and CAB are incompatible and CAB hinders the nucleation of PLA remarkably.In the study of crystallization behavior and properties of PLA/sisal composites, DSC was used to measure melting and cold crystallization of all components. The heat stability of all five components was compared through TGA measurements. Universal tensile testing machine was used to measure the tensile properties of five samples of all five components. And then storage modulus and tanδof neat PLA and composites before and after annealing were measured through DMA. At last, the isothermal crystallization morphology of all components were observed by polarizing microscope. All results above showed conclusions as follows:the addition of U-sisal promoted the crystallization of composites more evidently than A-sisal and S-sisal and the modulus of composites were improved. After annealing, storage modulus and Young modulus were both decreased, compared with components not-annealed. It was confirmed that annealing did not improve mechanical properties of all components.