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SYNOPSISThe presence of wall slip during the flow of polymeric melts has significant ramifications on the melts' processability. In this study, the effects of materials of construction and surface roughness on the wall slip behavior of a linear low density polyethylene were investigated, using capillary flow. Capillaries, constructed from copper, stainless steel, aluminum, and glass, were used. The inner surface roughness of the capillaries were characterized by the employment of a profilometer and scanning electron microscopy. The roughness profiles of copper capillaries were also altered by the employment of chemical etching. Using Mooney's analysis, the wall slip velocity values were determined to be in the range of 0.09 to 1.34 mm/s. The wall slip velocity values were the highest for stainless steel and were negligible for aluminum. The relative work of adhesion values of polyethylene were the smallest for stainless steel and copper and the highest for glass. Overall, the wall slip velocity values increased with decreasing surface roughness of the capillaries and with decreasing work of adhesion.

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SUMMARYThe effect of zinc borate (ZnB), borophosphate (BPO 4 ), and organoclay were studied to improve the flame retardancy of polyamide-6 composites containing organic phosphinates. The flame retardancy of polyamide-6 composites was investigated using limiting oxygen index (LOI), Underwriters Laboratories (UL-94) standard, thermogravimetric analysis, Fourier transform infrared spectroscopy, and mass loss calorimeter. The addition of 15 wt% aluminum phosphinate (AlPi) increased the LOI value from 22.5 to 29.5, and V0 rating was obtained from UL-94 test. The addition of organoclay, ZnB, and borophosphate does not change the predominant gas phase mechanism of AlPi during LOI and UL-94 tests. The addition of organoclay increased the condensed phase mechanism of AlPi physically by the protective effect of layered silicate, whereas the addition of ZnB increased the condensed phase mechanism of AlPi chemically by the formation of boron aluminum phosphate species deducted from mass loss calorimeter studies.

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