Different density rigid polyurethane foams (RPUF) filled with various expandable graphite loadings were fabricated by cast molding. The flame retardant properties of these composites were assessed by limiting oxygen index and horizontal and vertical burning tests. The results showed that the flame retardant efficiency got better with increase in the foam density at the fixed EG weight percent or with increase in the EG weight percent at the fixed foam density. After burning, the low density (0.065 g/cm 3 ) pure burned RPUF produced the highly collapsed and carbonized material, while the high density (0.510 g/cm 3 ) pure RPUF had little change in size and had reduced destruction of the material. Moreover, the scanning electronic microscope (SEM) observation showed that the higher density EG/RPUF composites had a more compact outer layer (burned layer) after burned, in which more wormlike materials composed of expanded graphite particles appeared. In addition, higher foam density led to less plastic deformation in the interface layer between the burned and the inside layers. These results indicated that a weight percent of a flame retardant additive that achieves satisfactory flame retardancy for a certain density foam cannot effectively be applied for another density foam.

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The crystalline morphologies of isothermally and nonisothermally crystallized poly(phenylene sulfide) (PPS) and its blend with polyamide 66 (PA66) were investigated by polarized optical microscopy with a hot stage. The spherulite superstructure of PPS was greatly affected by crystallizable PA66; a Maltese cross was not clear, and the impingement between spherulites disappeared. This could be ascribed to the formation of small crystals of PA66, which filled in the PPS lamellae. The nonisothermal crystallization behavior was also measured by differential scanning calorimetry. The presence of PA66 changed the nonisothermal crystallization process of PPS.The maximum crystallization temperature of the PPS phase in the blend was higher that that of neat PPS, and this indicated that PA66 acted as a nucleus for PPS. Also, the compatibilizer poly(ethylene-stat-methacrylate) (EMA) was added to modify the interfacial interplay of the PA66/ PPS blend system. The addition of EMA greatly influenced the nonisothermal crystallization process of the PPS phase in the blend system.

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The isothermal crystallization of poly(phenylene sulfide) (PPS) and its glass fiber (GF) reinforced composite has been investigated by differential scanning calorimetry (DSC) and polarized optical microscope (POM) equipped with a hot stage. During the isothermal crystallization process of PPS the Avrami exponent value decreases with time, indicating the change of crystallization mechanism and presence of mixed growth mechanism (bidimensional and three‐dimensional growth of crystals). The presence of GF greatly accelerates the bulk crystallization rate of PPS and changes the crystalline morphology of PPS from the spherulites to transcrystallization. And the reason for development of transcrystallization is considered to be relevant with the compatibility of the interface between GF and PPS. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers