Computer Analysis of RIM Moldability from the Density Distribution in Molded Products

Abstract

Under the worldwide campaign to “save resources and energy,” automobiles have been improved by reducing weight and increasing fuel efficiency. In Japan the use of urethane bumpers which meet these objectives has been steadily increasing. However, the manufacture of polypropylene bumpers as a substitute is also increasing, due to cheaper starting materials. The RIM urethane technology is very well suited to the production of parts that are large in size and complicated in shape. The problems with moldability arise when parts are made thinner, larger and when cycle time is reduced. These problems connected with moldability can be solved to some extent by optimization of the molding conditions, by better mold design and by selection of a better urethane system. However, the development of a new urethane system requires many experimental trials to optimize it because of the many variables involved, such as catalysts, isocyanates, polyols, blowing agents, temperature of starting materials, etc. At the present time there are only a few papers in literature discussing problems associated with the mold-ability of RIM systems. In this paper, computer techniques suitable for the optimization of physical properties and moldability of RIM systems will be discussed.