Epitaxial Crystallization Behavior Research Of Poly(L-Lactic Acid)/Poly(?-Caprolactone) On Oriented Polyethylene Substrate

Epitaxial crystallization is an effective means to control the micro structures of polymer materials. Epitaxial crystallization behavior of pure polymer has been studied by many material researchers. On the other hand, blending is a very convenient way to develop new materials, which can combine excellent properties of every component. We have studied Poly(L-lactic acid)/Poly(?-caprolactone) blends'properties and epitaxial crystallization on the highly oriented polyethylene substrate, as well as the mutual influence of the components when the blends are crystallizing induced by PE films.1. PLLA/PCL blends are immiscible. PCL's thermal stability is better than PLLA and two-step thermal degradation is observed by TGA. With the study of 6:4,5:5,4:6 of blend samples, PLLA component turns into the continuous phase from the dispersed phase, which means phase inversion occurs. PLLA/PCL blends are characterized by XRD and we have found PLLA component in the blends always generates a form crystal at 120? regardless of melt crystallization or cold crystallization.2. PE film is homemade and used to introduce PLLA/PCL blends' Epitaxial crystallization. PLLA and PCL are highly oriented on the PE substrate and PE film show strong heterogeneous nucleation ability for PLLA and PCL. Epitaxial crystallization of PCL on PE film takes place with its molecular chains parallel to the PE molecular chains. Epitaxial cold crystallization of PLLA occurs with its lamellae oriented in two directions. The angle is measured as approximately 55°. While most molecular chains of PLLA are vertical to the molecular chains of PE.3. Further research showed that small amounts of PCL components inhibit the epitaxial cold crystallization of PLLA components significantly. Increasing content of PCL leads to the more pronounced inhibition. When the PCL content is more than 30%, the epitaxial cold crystallization of PLLA can not take place. However the existence of PLLA components can not significantly affect the epitaxial crystallization of PCL. When the PLLA content is more than 50%, the epitaxial crystallization of PCL can still occur on oriented PE substrate.