Nucleation effect of clay on crystallization of polypropylene under carbon dioxide

We investigated the crystallization growth of isotactic polypropylene (PP)/clay phase-separated microcomposites under carbon dioxide (CO2) by in situ observation with a specially designed high-pressure visualized cell. The number density of the spherulite was larger and the size of the spherulite filled in the whole space was smaller in the PP/clay microcomposites than those in the neat PP, indicating nucleation effect of clay on the crystallization of PP. The increase of the number density of the spherulite by addition of clay was much larger under CO2 than that under air at ambient pressure, suggesting that the nucleation effect of clay is enhanced under CO2. Microscopic observation and small angle X-ray scattering measurement revealed that lamellae grow from the surface of the clay tactoids, and the lamellae and lamellar stacks arrange irregularly due to the growth of lamellae from the irregular shaped clay in different directions. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers