Abstract
To overcome PLLA’s poor crystallization capability, using nucleating agent as crystallization improvement strategy was performed in this study. PPAPH as PLLA’s an organic nucleating agent was firstly synthesized, and then PLLA was blended with different PPAPH loading through melting blend method, the resulting influences of PPAPH on PLLA’s performances were investigated using the relevant testing instruments. Melt-crystallization revealed that PPAPH played important role in promoting PLLA’s crystallization through providing effective sites of heterogeneous nucleation, and effect of PPAPH loading on PLLA’s melt-crystallization was very poor, indicating that low PPAPH loading could cause PLLA to possess powerful crystallization capacity. In addition, the relative low final melting temperature was beneficial for PLLA/PPAPH’s crystallization. However, an increase of cooling rate during cooling stage weakened PLLA/PPAPH’s crystallization capacity. PLLA/PPAPH’s cold-crystallization suggested that PPAPH had an inhibition effect on cold-crystallization process to some extent. Melting behaviors depended on heating rate and previous crystallization including melt-crystallization at various cooling rates and isothermal crystallization at various crystallization temperatures. PPAPH enhanced PLLA’s fluidity, tensile modulus and tensile strength. Unfortunately, PLLA’s transmittance was seriously weakened as PPAPH loading increased, as well as the elongation at break continuously decreased.
Keywords: poly(L-lactide); phenylacetic hydrazide; heterogeneous nucleating agent; melt-crystallization; fluidity