Effect of D-isomer content on Strain Induced Crystallization Behaviour of Poly(Lactic) Acid Polymer under High Speed Uniaxial Drawing

Abstract Stereo regularity in polymer materials is known that can gives significant effect on the development of semi crystalline structure via a strain induced crystallization. The content of d -isomer plays an important role in the stereo regularity of Poly (lactic acid) polymer (PLA). This study is about the effect of d -isomer contents of 2%, 4% and 12% under uniaxial drawing with the speed of 6 s-1 at temperature 80  ° C on the crystallization behaviour of Poly(lactic acid). The evolution of PLA samples crystallization were studied based on WAXD patterns data recorded within time resolved stretching experiment at synchrotron radiation. This study found that the crystallization began after drawing has ceased completely for all samples regardless the content of d -isomer. The uniaxial drawing only gives affects on the increment of polymer molecular orientation prior to the onset of crystallization. The crystallization occurred after deformation and it was influenced by the polymer molecular orientation, where, the crystallization rates and degree of crystallinity is low when d -isomer content is high. PLA random copolymer with 12% d -isomer have crystallized at draw ratio 6.0, while compared with the PLA random copolymer containing 2% and 4% d -isomer have crystallized at draw ratio around 3.0. The rate of crystallization for 12% d -isomer was just 0.28 s-1 when compared with around 4.0 s-1 for PLA samples with 2% and 4% d -isomer contents respectively. The PLA random co-polymer studied in this work have been crystallized into α’ crystal structure with some degrees of crystallinity. The degree of crystallinity is inversely correlated and the size of crystallite is directly correlated with the d -isomer content.