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

Abstract

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 β-crystalline form was produced in the samples containing 0.15 wt% GA and more than 0.17 wt% Cd(OH)2. The content of β-crystalline form was maximum, i.e. KDSC = 65.4% and KWAXD = 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 β-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 β nucleator (cadmium glutarate).