Enhancing cold crystallization of poly(L-lactide) by a montmorillonitic substrate favoring nucleation

A montmorillonite (MMT) with nucleating surface (NMMT) supported by chemically calcium phenylphosphonic acid (PPCa), an effective nucleant for poly(L-lactide) (PLLA), was prepared through the chemical reaction between phenylphosphonic acid (PPOA) and calcium ion on the surface of MMT. Then, NMMT was introduced into PLLA via simple melt blending. The overall isothermal cold crystallization rates of PLLA were faster in the blends than in neat PLLA, indicative of the nucleating effect of the NMMT in the blends. The crystal structure of PLLA and its blends remained unchanged despite the addition of NMMT in the blends. For the nonisothermal cold crystallization, the crystallization process of PLLA was accelerated by increasing both heating rate and the NMMT contents. The Avrami equation and the combined Ozawa-Avrami model could describe it successfully. Moreover, the activation energy for nonisothermal cold crystallization of neat PLLA and its blends based on Friedman equation was estimated. (C) 2014 Elsevier B.V. All rights reserved.