Non-isothermal crystallization kinetics of iPP/sPP blends

Non-isothermal crystallization and subsequent melting behaviour of iPP/sPP blends of various compositions were investigated by differential scanning calorimetry (DSC). Results revealed that sPP crystallizes at a slower rate than iPP. This effect is attenuated when the cooling rate is increased up to 20 °C/min and 25 °C/min. DSC scans showed that stability of primary crystallites of sPP and perfection of iPP crystallites were both increased by decreasing cooling rate. Effective activation energy (image) of sPP, calculated using Friedman iso-conversional method, was found to be lower in iPP/sPP blend than in neat sPP whereas image of iPP is not modified. Results were analysed through Avrami, Ozawa and Mo models. They both showed a decrease of crystal growth dimensionality for both iPP and sPP in iPP/sPP blends compared with neat iPP and sPP. The kinetic parameters U and Kg were determined by the Hoffman–Lauritzen theory.