Characterization and Crystallization Kinetics of in situ Prepared Poly(propylene terephthalate)/SiO 2 Nanocomposites

A series of poly(propylene terephthalate)/silica nanocomposites containing 0.5, 2, 3.5, and 5 wt.‐% SiO 2 were prepared by application of the in situ method. The nanocomposites with 3.5 and 5 wt.‐% SiO 2 showed an insoluble content because of branching or cross‐linking of the macromolecules, as a result of reaction with the surface hydroxyl groups of silica nanoparticles. Wide‐angle X‐ray diffraction (WAXD) patterns of the composites were identical with that of neat poly(propylene terephthalate) (PPT). Crystallization kinetics under both isothermal and non‐isothermal conditions was extensively studied. It was found that crystallization rates are enhanced in materials with low silica content, while they are depressed for those with 3.5 and 5 wt.‐% SiO 2 . Finally, the melting behavior of the samples was investigated. Branching or cross‐linking of the macromolecules due to bonding with silica nanoparticles resulted in reduced recrystallization on heating.