The crystallization kinetics of polypropylene (PP) with or without sodium benzoate as a nucleating agent were investigated by means of DSC and polarized optical microscopy in isothermal and nonisothermal modes. A modified Avrami equation was applied to the kinetic analysis of isothermal crystallization. The addition of the nucleating agent up to its saturation concentration increased the crystallization temperature by 15 °C and shortened both the isothermal and nonisothermal crystallization half‐times. It was concluded that the sodium benzoate acted as a good nucleating agent for α‐form PP. By adding the nuclefier to PP, adequately controlled spherulites increased the mechanical properties including especially the Izod impact strength and shortened cycle time of PP. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1001–1016, 2001

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ABSTRACT:The effect of sodium benzoate on the isothermal crystallization behavior of isotactic polypropylene (iPP)/ethylene-propylene rubber(EPR) blends was investigated using differential scanning calorimetry. Dynamic mechanical and physical properties of the iPP/EPR blends nucleated with sodium benzoate were also measured. It was found that the crystallization behavior and physical properties such as heat deflection temperature (HDT), flexural modulus, and impact strength were strongly affected by the competition between the nucleating effect of EPR attributed to its partial compatibility with iPP and the simple addition of the amorphous component, as well as the nucleating effect of sodium benzoate. High impact strength was achieved by addition of EPR and sodium benzoate to iPP.