The Nucleated Poly(L-lactic acid): The Role of a Phenylacetic Hydrazide Derivative

The melt-crystallization, cold-crystallization, melting behaviors, thermal stability, and optical properties of poly(L-lactic acid) (PLLA) nucleated by a phenylacetic hydrazide derivative (DAPH) were investigated. The melt-crystallization confirmed DAPH’s heterogeneous nucleation role in improving PLLA’s poor crystallization capability, concurrently DAPH loading, cooling rate and final melting temperature were three key factors affecting PLLA’s melt-crystallization behaviors. The results from cold-crystallization indicated that the addition of DAPH could accelerate PLLA’s cold-crystallization via cold-crystallization peak’s shift toward the lower temperature side as DAPH loading increased. Through analysis of PLLA/DAPH’s multiple melting behaviors after melt-crystallization, it was found that DAPH loading, the previous melt-crystallization and heating rate determined PLLA/DAPH’s melting processes after melt-crystallization; and PLLA/DAPH’s melting processes after isothermal crystallization depended on the previous crystallization temperature. A drop in thermal decomposition temperature for 5 wt.% mass loss suggested that pure PLLA has better thermal stability compared with PLLA/DAPH. Additionally, the introduction of DAPH could not improve PLLA’s transparency, in contrast, the haze of PLLA was increased greatly owing to the existence of DAPH.