The crystallization behaviour of isotactic polybutene-1

Abstract

The crystallization behaviour of different commercial grades of isotactic polybutene-1 was investigated and an experimental set-up was designed for this research study. The experimental set-up constructed provides both fast-cooling of the sample and the recording of the growth of spherulites as a real time movie. The radial growth rate of the spherulites were observed to be higher for the grades with higher molecular weights. The results were found to fit to the Lauritzenn-Hoffman crystallization theory, and this theory is used to calculate the lateral surface free energy, σ, and fold surface free energy, σe. The lateral surface free energy was found to be 10.4 erg/cm2 for all the grades investigated. The fold surface free energy calculated to be between 15.5 to 17.4 erg/cm2 . The fold surface free energies and the crystallization rates do not exhibit any dependence on the molecular weight of the polymer. The polymer containing nucleating agents has the highest crystallization rate. It was observed that the likelihood of deviation from spherical shape is greater for the grades with lower molecular weights.