Thermal and flow property-morphology relationship of sugarcane bagasse fiber-filled polyamide 6 blends

The structure-property relationship of sugarcane bagasse fiber-filled polyamide 6 blends at different blend compositions has been investigated. Blends were prepared in the composition of wt % PA6/wt % bagasse as follows: 98/2, 95/5, and 90/10 for three fiber length ranges (<100, <250, and <500 mum) using a twin-screw extruder. Thermal properties were evaluated by measuring the glass transition temperature T-g, enthalpy of fusion DeltaH(f), crystallinity X-c and thermogravimetry, TG. Results showed that T-g of the composites changed with change in fiber loading and length. The X-c as well as DeltaH(f) of the blends reduced to almost half its value for the neat PA6. The thermogravimetric curves TG showed that the thermal stability of the composites was lower than that of the neat PA6. Rheological properties were studied as a function of fiber loading, fiber length, shear rate, and temperature. The viscosity of composites increased with increasing fiber loading and length at low shear rates but decreased below that of neat PA6 at high shear rates. It was also found to be temperature sensitive, and influenced by fiber lengths particularly at higher temperatures. The morphology of the blends was studied using a Leica laser scanning confocal microscopy at two different regions: at the wall, and the core. The micrographs of the blends showed that fibers present in the form of bundles were found at the wall of the extrudates and increased in volume with increase in both length and concentration, at the same temperature and shear stress. In the core region, there is laminar flow, presenting striation morphology, with the omnipresent bundles of fibers dispersed in the matrix. At higher shear rates, the bundles were pushed to the wall. (C) 2004 Wiley Periodicals, Inc.