Crystallization and melting behavior of polyester/clay nanocomposites

Polyester/clay nanocomposites were prepared by melt compounding with different clay loadings. Comparing against neat polyester resins, the crystallization and multiple melting behavior of the nanocomposites was investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Nanoclay filler is an effective heterogeneous nucleating agent, as evidenced by a decrease and an increase in the crystallization temperature for both cold and melt crystallization of polyesters, respectively. The degree of crystallinity was found to increase with increasing clay content, due to heterogeneous nucleation effects by the addition of a nanofiller. For the annealed samples, multiple melting peaks were always observed for both neat polyester and its nanocomposites. The origins of the multiple melting behavior are discussed, based on the DSC and XRD results. Interestingly, an 'abnormal' high-temperature endothermic peak (T-m,T-3) at about 260 degreesC was observed when the nanocomposite samples were annealed at higher temperatures (eg greater than or equal to 240degreesC). The constrained polyester crystals formed within intercalated clay platelets due to confinement effects were probably responsible for this melting event at these higher temperatures. (C) 2004 Society of Chemical Industry.