Knit lines in reaction injection moldings

Abstract Knit lines in reaction injection molding (RIM) are formed when a fluid flow front passes through the mold cavity and must pass around objects in its path. Factors were ordered in importance of their effects on the deterioration in mechanical strength associated with knit lines. In order of decreasing importance, reactant temperature, mold temperature, and relative location (from the product) of the knit line sample were found to affect the knit line strength.