Material behaviourNucleation effect of layered metal phosphonate on crystallization of isotactic polypropylene

The effect of layered metal phosphonate, zinc phenylphosphonate (PPZn), on the crystallization behavior of isotactic polypropylene (iPP) was investigated by differential scanning calorimetry. PPZn shows excellent nucleating effect on iPP. The nucleation efficiency of the composites reaches 32% even at very low loading of 0.02 wt% PPZn. For 0.1 wt% PPZn, the crystallization half-time of the composite decreases from 19.42 to 1.87 min at 134 °C, compared with pure iPP. The isothermal crystallization data were further analyzed by the Avrami model. The values of the Avrami exponent of the composites are comparable to that of pure iPP, indicating that the presence of PPZn does not change the crystallization mechanism of the matrix. The presence of PPZn increases significantly the nuclei density of iPP but has no discernible effect on its crystalline structure, evidenced by polarized optical microscopy and wide angle X-ray diffraction measurements.