Crystallization Behavior And Mechanical Properties Of Poly(L-lactide)/Poly(Ethylene Adipate) Blends

Poly(L-lactide) (PLLA) has attracted much more attention because of its biodegradability, biocompatibility as well as its higher strength and modulus.At present, PLLA has been widely used in bio-medicine and packaging areas.However, its inherent brittleness and slow crystallization rate restrict its further application. In this work, we prepared a series of PLLA and poly(ethylene adipate) (PEA) blends by a solution casting method, in order to enhance the toughness and crystallization of PLLA.Firstly, the effect of PEA contents on miscibility, crystallization behavior and mechanical properties of PLLA/PEA blends was investigated, and the molecular weight of PEA was 1K. The miscibility results showed that there were only one glass transition temperature (Tg) in PLLA/PEA-1K blends,which were lower than that of neat PLLA, indicating that PLLA and PEA-1K were misicible. The results of nonisothermal crystallization showed that with the increase of PEA-1K content, the crystallization enthalpy of PLLA was increased, indicating that PEA-1K enhanced the nonisothermal crystallization of PLLA. Similar to the nonisothermal crystallization process, PEA-1K increased the isothermal crystallization rates of PLLA as well. Besides, the strain at break of PLLA/PEA-1K was increased with the increase of PEA contents.Secondly, we investigated the effect of molecular weights of PEAs on miscibility, crystallization behavior and mechanical properties of PLLA/PEA blends. Acorrding to Tg, PLLA/PEA-1K and PLLA/PEA-4K blends were miscible, while PLLA/PEA-8K blends were immiscible. The nonisothermal crystallization showed that all of the PEAs enchanced the nonisothermal crystallization behavior of PLLA by increasing the nonisothermal crystallization enthalpy, but the nonisothermal crystallization enthalpy of PLLA decreased with the increase of molecular weights of PEA. The results of isothermal melt crystallization showed that the crystallization rates of PLLA were increased by PEA-1K and PEA-4K, while decreased by PEA-8K because of its immiscibility with PLLA. But the crystallization mechanism of the PLLA/PEA blends all remained unchanged. Besides, the strain at break of PLLA/PEA blends were increased first and then decreased with the increase of molecular weights of PEA, but all higher than that of neat PLLA.The main work of this paper was to investigate the effects of both the contents and molecular wights of PEAs on mechanical properties and crystallization behaviors of PLLA. The results showed that by regulating the contents and molecular weights of PEA, both the mechanical properties and crystallization behaviors of PLLA can be optimized, so that the application of PLLA can be further widened.