Non-isothermal crystallization kinetics of thermoplastic vulcanizate based on polypropylene/ polybutadiene rubber in the presence of polybutadiene modified with acrylic acid as compatibilzer

Non-isothermal crystallization kinetics of Polypropylene (PP) melt as a continuous phase of thermoplastic elastomers (TPEs) based on polypropylene / polybutadiene rubber (TPE1: PBR/PP) and polybutadiene rubber / acrylated-polybutadiene compatibizer / polypropylene (TPE2: PBR/ Ac-PBR /PP) as well as their the corresponding thermoplastic vulcanizate(TPV) samples (TPV1 and TPV2) were investigated using Ozawa's kinetic model. The results of the DSC data and the Ozawa model show that the Ac-PBR compatibilizer, increases the onset and the final temperature of crystallization and make the crystallization region narrower. Dynamic vulcanization also results in shifting the onset and the final crystallization temperatures to lower values. The temperature (Tc) and the half-time for crystallization (t_(1/2)) of all blends decrease with increasing cooling rate. The crystallization rate constant and the ozawa model exponent (m) for four different temperatures (110, 115, 120 and 130 C °) were obtained by linear regression method. The exponent of ozawa model changes with increasing degree of molten/crystal conversion. While the “m” value for the pure PP varies from (1.4 at 110℃) to (3 at 120 ℃), these values for TPE1 range from (1.7 at 110℃) to (3.3 at 120℃) and for TPE2 are higher and varies from (1.1 at 110℃) to (4 at 125℃). The maximum value of the crystallization rate constant (KC ) for all blends occurs at approximately 50% relative crystallinity; the highest crystallization rate constants obtains for TPE2.