DETERMINATION OF THE INTERRELATIONSHIPS BETWEEN PROCESSING CONDITIONSAND PROPERTIES OF AN INJECTION-MOLDED SILICONE RING USING AN EXPERIMENTAL-DESIGN

The effects of injection-molding parameters on the mechanical-physical properties of a liquid silicone rubber (LSR) injection-molded ring we re studied through an experimental design. The effects of the changeov er point (volume or pressure driven), runner (hot or cold), hold press ure, mold temperature and injection flow rate variations were evaluate d based upon the responses related to both material properties (ultima te elongation and tensile stress in a tensile test, swelling in hexane , hardness, density) and ring properties (cross sectional diameter, we ight, volume). It was determined that ring density is not dependent on the parameters studied. The mold temperature appeared to be a very in fluential parameter, especially concerning material characteristics: i t affects the swelling ratio, hardness, and ultimate properties, but w eight and volume are only affected when the cold runner is used. The h old pressure has an effect on both the weight and volume of the ring. The type of changeover used (volume or pressure) has no effect when a cold runner is used, but affects the weight, volume, and ultimate prop erties of the ring, when a hot runner is used. The injection flow rate did not affect the observed characteristics.