METAL INJECTION-MOLDING - EFFECTS OF THE VINYL-ACETATE CONTENT ON BINDER BEHAVIOR

Binder formulation is one of the key steps in the development of metal injection molding technology. The binder chosen for this study is a b lend consisting of ethylene-vinyl acetate co-polymer and beeswax. The preparation of the binder blends was carried out in the Haake Rheocord 90 mixer. The effects of the vinyl acetate content and the polymer/wa x ratio on the thermal and rheological properties of the binder were s tudied using a differential scanning calorimeter, a thermomechanical a nalyzer, and a controlled-stress rheometer. The results indicated that the melting (T-m) and softening (T-s) temperatures of the binder are reduced by the addition of increasing wax proportion. Higher vinyl ace tate content also resulted in a lower value of T-m and T-s. The viscos ity of the binder is inversely proportional to the wax content and the temperature. The results obtained from this study provide the necessa ry information for determining the operating window of binder mixtures suitable for injection molding. (C) 1997 Elsevier Science S.A.