Acceleration mechanism in critical nucleation of polymers by epitaxy of nucleating agent

Abstract

Effect of epitaxy of nucleating agent (NA) on nucleation of polymers was investigated based on kinetic study. Nucleation rate (I) of polymers is given by I = I0 exp(-ΔG/kTc) (1), where I0 is prefactor, ΔG is free energy for forming critical nucleus, k is Boltzmann constant and Tc is crystallization temperature. We reported in the previous paper that decreasing the size of NA is important for increasing I 0, i.e., I. In this study we focus on ΔG dependence of I. In the case of heterogeneous nucleation, ΔG is a function of interfacial free energy between NA and nucleus (Δσ). Δσ/σ varies between 0 and 1 where σ is lateral surface free energy of nucleus. Δσ/σ of isotactic polypropylene (iPP) mixed with three NAs were between 0.13 and 0.23, which were evaluated by the fit of eq 1 to the experimental data of I. I increased by 38 orders of magnitude for ΔT = 30 K with decreasing Δσ/σ from 1 to 0. In the case of NA, I increased by 60 times for δT = 30K with decreasing Δσ/σ from 0.23 to 0.13. I significantly depends on Act. Therefore we concluded that ΔG(Δσ) is essentially important for acceleration of nucleation. ©2009 The Society of Polymer Science, Japan.