Influence of Crystallization on Intercalation, Morphology, and Mechanical Properties of Polypropylene/Clay Nanocomposites

TLDR

PP/Clay nanocomposites were prepared by melt extrusion of maleic anhydride‑modified polypropylene with organophilic clay. Higher crystallization temperatures increased intercalation of PP‑MA chains between clay galleries, while higher clay content reduced intercalation; clay acted as a nucleating agent, decreasing spherulite size and causing segregation at spherulite boundaries, with extensive intercalation occurring at high Tc due to prolonged solidification, and intercalation strongly depended on melt residence time, ultimately enhancing the dynamic storage modulus in the 70–130 °C range.

Abstract

Intercalated nanocomposites of polypropylene (PP)/clay (PPCNs) were prepared by a melt extrusion process using maleic anhydride modified PP (PP-MA) and organophilic clay. The extent of intercalation of PP-MA chains in the space between silicate galleries increased with crystallization temperature Tc and decreased as clay content increased. As compared to matrix PP-MA, the dispersed clay particles in the PP-MA matrix acted as a nucleating agent and lowered the spherulite dimension with increasing clay content as revealed by light scattering experiments and polarizing optical microscopy. The PPCN crystallized at high Tc showed that a certain extent of segregation of the dispersed clay particles takes place around the boundary of the spherulites (interspherulite). Extensive intercalation occurred during crystallization, especially at high Tc due to the long time for full solidification of the melt. The degree of intercalation of PP-MA chains in the silicate galleries strongly depends on the time in the molten state. The effect of the intercalation through organophilic interaction on the dynamic storage modulus of the PPCNs crystallized in the temperature range of 70−130 °C has been emphasized.