Effect of an In-Situ Nucleating Agent on the Polymorphs and Mechanical Properties of Isotactic Polypropylene

The influence of glutaric acid (GA)/cadmium hydroxide [Cd(OH)(2)] mixtures on the crystallization and properties of isotactic polypropylene (iPP) was investigated by means of differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), polarized light microscopy, and mechanical tests. It was found that the beta-crystalline form was produced in the samples containing 0.15 wt% GA and more than 0.17 wt% Cd(OH)(2). The content of beta-crystalline form was maximum, i.e. K-DSC = 65.4% and K-WAXD = 71.4%, when the sample was doped with GA (0.15 wt%)/Cd (OH)(2) (0.20 wt%) (the molar ratio of GA: Cd(OH)(2) was 1:1.2). It was also found that GA/Cd(OH)(2) mixtures not only induced the b-crystalline form but also made spherulites smaller. The results of mechanical tests showed that the toughness of iPP was greatly improved by bicomponent nucleator, while the stiffness decreased a little. Fourier transform infrared spectroscopy analysis indicated that an in-situ chemical reaction occurred between GA and Cd(OH)(2) during melt blending, yielding an effective beta nucleator (cadmium glutarate).