Modified PLLA: effect of BPADD on properties

Abstract

Poly(l-lactic acid) (PLLA) modified by a new organic nucleating agent, N,N′-dodecanedioic bis(piperonylic acid) dihydrazide (BPADD), was fabricated, and its crystallization, melting behavior, thermal stability, fluidity and mechanical properties were investigated. The melt-crystallization behavior proved that BPADD could bring about a fast nucleation rate to promote the crystallization of PLLA; 2 wt% BPADD exhibited the best crystallization accelerating effect due to having the highest crystallization onset temperature and the highest melt-crystallization temperature. However, PLLA/3% BPADD had the largest melt-crystallization enthalpy. In addition, the frontier orbital energy indicated that the nucleation effect of BPADD on PLLA might be attributed to intermolecular interaction. The melt crystallization also depended on two critical factors, the cooling rate and final melting temperature. An increase in BPADD content led to greater inhibition of crystal growth during cold crystallization. The differences in the melting behavior of PLLA/BPADD samples reflected the previous crystallization process, the heating rate and BPADD content. BPADD was harmful to maintaining the thermal stability of PLLA; however, the intermolecular interaction could prevent the decomposition onset temperature from continuously decreasing. The usage of BPADD resulted in better fluidity and higher tensile strength; the tensile modulus and elongation at break were associated with BPADD content.