Effect of Process Variables on Mechanical Properties of Injection Molded HDPE

HDPE (HIGH DENSITY POLYETHYLENE) was moulded with 3 different material temperatures and 5 different injection pressures. The mechanical properties like impact strength, tensile strength and flexural strength were determined. The Izod impact strength (notched) was improved when the injection pressure and melt temperatures were increased. The tensile strength was slightly decreased. The flexural strength was increased slightly. The effect of injection pressure was determined by extrapolating from first two levels to other levels (3,4,5) by using simultaneous equation method at constant temperature. Similarly using first three levels, the values were computed by Lagrange method of extrapolation to 4 and 5 levels of injection pressure at each temperature levels of moulding. The effect of cooling time was also determined. The values are in good agreement with simultaneous equation method. Slightly higher values are obtained in Lagrange method.