The Effect of Montmorillonite Modification on Crystallization Behaviour of Polypropylene/Montmorillonite Composites

This paper reports the preparation of organic montmorillonite (OMMT) modified by octadecylamine and polypropylene/montmorillonite (PP/MMT) composites produced by the method of melt compounding. The effect of MMT modification degree on the crystallization behaviour of PP was emphasized by X-ray diffraction (XRD), polarizing optical microscopy and differential scanning calorimetry (DSC). Interlayer d-spacings of 3.02 nm, 1.27 nm and 2.59 nm were detected for MMT modified by octadecylamine, Titivate coupling agent and commercial OMMT, respectively. The spherulite size and the crystallinity of the composite decreased and the number of spherulites increased with the interlayer spacing of OMMT. The values of t 1/2 and F(T) for PP crystallisation decreased with the interlayer spacing at a given cooling rate or a given relative crystallinity degree, indicating that MMT with a larger gallery height could accelerate the crystallization rate of PP more efficiently. Moreover, the composites containing OMMT modified by octadecylamine exhibited better mechanical properties in comparison to those incorporating OMMT modified by Titivate coupling agent and commercial OMMT, indicating that primary amine was one of the best potential surfactants for MMT modification. It was concluded that full modification of OMMT by octadecylamine was more beneficial to the crystallization of PP and hence caused a positive effect on the mechanical properties of the composites.