Blends of low-density polyethylene (LDPE) with Polystarch N were prepared by extrusion. Tensile properties, thermal behavior, and natural weathering of these blends were investigated as a function of blend composition. The addition of Polystarch N to the matrix decreased the tensile properties and the degree of crystallinity of LDPE when the proportion of Polystarch N increased in the blend, as revealed by differential scanning calorimetric studies. Scanning electron microscope analysis of the blends retrieved after being exposed to natural weathering showed that natural degradation increased with increase in the amount of Polystarch N in the LDPE and is ascribed to higher extent of chain scission as revealed by Fourier transform infrared spectroscopy analysis.
SYNOPSISVariation of dynamic mechanical properties like storage modulus (E') and loss tangent (tan 6 ) with temperature show the presence of two transitions in the carboxylated nitrile rubber (XNBR) molded in the presence of zinc oxide (ZnO). The low-temperature transition is due to the glass-rubber transition (T,) of XNBR, and the high-temperature transition is due to formation of ionic clusters. Incorporation of reinforcing silica filler makes the hightemperature transition more prominent and high filler loading causes a shift of the transition temperature to the higher side. It is believed that the rubber-filler interaction in the cluster region causes striking changes in the variation of E and tan 6 with a double-strain amplitude (DSA).
Processability, curing characteristics and vulcanizate properties of EPDM compounds containing ground waste EPDM (W-EPDM) have been studied. Ground waste was prepared from factory scraps, using a mechanical grinder with silicon carbide abrasive wheel rotating at 2950 rpm. The particle size shows a range between 2 and 50 μm, with an average size of 10 μm. Particle surface seems to be rough and convoluted and mild oxidation during the abrasion enhances the aggregation of particles. Mooney scorch time and the maximum rheometric torque of the EPDM compound decrease gradually with increasing W-EPDM content. Migration of curatives between the virgin rubber and waste rubber phases is believed to be the reason for the variation in the curing behavior. The processability of the EPDM compound shows improvement on addition of W-EPDM (that is, both die swell and extrudate distortion are less). The vulcanizate properties of the W-EPDM-filled EPDM compounds reveal the reinforcing nature of the ultrafine W-EPDM particles. Comparison of W-EPDM with an inert filler like precipitated CaCO3 in an EPDM compound reveals the potential of W-EPDM as a cheap filler in EPDM compounds. It is also found that W-EPDM can be incorporated into the window seal compound formulation and the drop in properties even at 100 phr of W-EPDM is within acceptable limit, thus providing a scope for on-site recycling of EPDM.
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