Blends of preirradiated polypropylene powder and syndiotactic 1,2polybutadiene: Isothermal and nonisothermal crystallisation kinetics

Purpose The purpose of this paper is to study the isothermal and nonisothermal crystallisation kinetics of pure polypropylene (PP), 1 kGy preirradiated PP and 1 kGy preirradiated PP/syndiotactic 1,2polybutadiene (s1,2 PB) (90/10) blends by differential scanning calorimetry. Design/methodology/approach The Avrami equation, modified Avrami equation, Ozawa equation and the treatment by combining the Avrami and Ozawa equation were used to analyse the isothermal and nonisothermal crystallisation of various samples. Findings The s1,2 PB acted as a heterogeneous nucleation agent during the crystallisation of the PP/s1,2 PB blends and accelerated the crystallisation rate. The Avrami exponent n of the blends implied that the isothermal crystallisation kinetics of the blends followed a threedimensional growth via heterogeneous nucleation. The modified Avrami equation was limited to describe the nonisothermal crystallisation process of pure PP and 1 kGy preirradiated PP, but it was successful for the blends. The treatment by combining the Avrami and Ozawa equation described appropriately the nonisothermal crystallisation process and obtained the kinetic parameter F(T) with specific physical meaning. The crystallisation activation energy for isothermal crystallisation and nonisothermal crystallisation of the blends was reduced due to the s1,2 PB acting as a heterogeneous nucleating agent during the crystallisation of the blends and accelerating the crystallisation rate. Research limitations/implications The Avrami equation, modified Avrami equation, Ozawa equation and the treatment by combining the Avrami and Ozawa equation were compared for analysis of the isothermal and nonisothermal crystallisation of samples. The crystallisation activation energy for isothermal crystallisation and nonisothermal crystallisation was also calculated according to the Arrhenius and the Kissinger method. Practical implications The fundamental research on the crystallisation properties of PP/s1,2PB blends is essential to understand the mutual effects of two components on their crystallisation mechanisms, facilitating to improve the mechanical properties of the final materials. Originality/value The isothermal and nonisothermal crystallisation behaviours of PP/s1,2 PB blends, especially preirradiated PP/s1,2 PB blends, have not been studied systematically yet, though PP/s1,2 PB blends were promising materials in terms of both PP toughening and the application of s1,2 PB thermal plastic elastomer.