Nonisothermal Crystallization, Melting Behaviors, and Mechanical Properties of Isotactic Polypropylene Nucleated with a Liquid Crystalline Polymer

The nonisothermal crystallization and melting behaviors of isotactic polypropylene (iPP) nucleated by a main chain liquid crystalline polyester (poly(4,4'-bis(6-hydroxyhexyloxy)biphenyl phenylsuccinate), PBDPS) as a beta-nucleating agent have been investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WARD), and polarizing optical microscopy (POM). The effect of PBDPS on the mechanical properties of iPP was also studied. The results showed that nonisothermal crystallization kinetics of pure iPP and iPP/PBDPS blends can be described by the Jeziorny and Mo methods. PBDPS can induce both alpha and beta crystals for iPP, with beta-nucleation playing the more prominent role. The relative content of the beta-crystal (k(beta)) increased as the PBDPS content increased and the cooling rate decreased. The k(beta) value reached 75%, even with a fast cooling rate of 40 degrees C/min. The elongation at break, flexural modulus, impact strength, and heat temperature (HDT) are improved by introducing PBDPS, while the tensile strength remains approximately the same.