Nonisothermal crystallization kinetics of isotactic polypropylene nucleated with a novel supported beta-nucleating agent

The introduction of beta-nucleating agent into isotactic polypropylene (iPP) is the most effective method to prepare beta-iPP. In this paper, iPP nucleated with a novel highly efficient supported beta-nucleating agent (NA100), calcium pimelate (CaHA) supported on the surface of nano-CaCO3, was prepared and its nonisothermal crystallization kinetic, melting characteristic, and crystallization activation energy are investigated and compared with those of pure iPP, nano-CaCO3 filled iPP, and beta-nucleating agent CaHA nucleated iPP. The results indicate that addition of nano-CaCO3 increases the crystallization temperature of iPP and has no influence on the crystal form of iPP. iPP and nano-CaCO3 filled iPP mainly crystallize in the form of a-crystal. Although NA100 and CaHA induce iPP to mainly form beta-crystal, NA100 nucleated iPP shows higher crystallization temperature, melting temperature, and beta-phase content than that nucleated with CaHA without supports. Nonisothermal crystallization kinetic is well described by the equations of Avrami and Mo, and the crystallization activation energy was calculated from Kissinger's method. It was found that the decreased crystallization activation energy is favorable to increase the crystallization rate and the content of beta-crystal. Although the content of CaHA in 5 wt% NA100 nucleated iPP was less than that in 0.1 wt% CaHA nucleated iPP, the former formed more beta-iPP than the latter, indicating that the beta-nucleating agent CaHA supported on the surface of nano-CaCO3 exhibits higher efficiency for preparation of beta-iPP than pure CaHA powder.