Effects of Malonic Acid Treatment on Crystal Structure, Melting Behavior, Morphology, and Mechanical Properties of Isotactic Poly(propylene)/Wollastonite Composites

Wollastonite is treated with a new surface modifier (malonic acid). The influence of malonic acid treatment on the crystallization and mechanical properties of polypropylene (PP)/wollastonite composites has been studied. The results of differential scanning calorimetry, wide angle X-ray diffractometry, and polarized light microscopy prove that malonic acid-treated wollastonite increases the relative content of beta-crystal form of PR The scanning electron microscopy shows that malonic acid-treated wollastonite has better compatibility with PP matrix than the untreated wollastonite. Higher beta-phase contents, smaller spherulite sizes, and better compatibility with PP matrix of the composites containing malonic acid-treated wollastonite result in improved impact strength and tensile strength, but lower flexural modulus. The results of Fourier transform infrared spectroscopy show that malonic acid reacts with the Ca2+ of wollastonite to form the calcium malonate, which acts as an effective beta-nucleating agent. POLYM. COMPOS., 31:966-973, 2010. (C) 2009 Society of Plastics Engineers