Reactive Processing of Polymers: A) Reactive Processing of Engineering Thermoplastics; B) Reaction Injection Molding of Polyurethanes

Abstract As a class of materials, engineering thermoplastics have enjoyed phenomenal growth in sales. The capital investment required to develop and introduce a new engineering thermoplastic has, however, increased dramatically. In response to these competitive pressures, engineering resin producers have increasingly focused their R&D efforts towards improving the performance of existing resins. One approach is to move chemistry from reaction vessels into processing equipment. This strategy is often referred to as reactive processing. Successful development of new engineering polymer grades by reactive processing calls for a multidisciplinary approach, with expertise required in chemistry, polymer science, polymer engineering, computer modeling and statistical process control. The first part of this paper will give a survey of the research work at Bayer Corporation on the synthesis of block copolymers, compatibilized blends and impact modifiers. Polyurethanes are inherently reactive processing polymers. They are usually processed as liquids, for example, for the manufacture of polyurethane foams and elastomers. The two-component polyurethane coatings fit also into this scheme. Polymerization takes place in the foam machine, in the molds, and on the painted substrate. The Reaction Injection Molding (RIM) technology exemplifies in a unique way the reactive processing of polyurethanes. RIM combines the processing of liquids and the forming of thermoset parts in a process which can match the cycle times of the injection molding of thermoplastics. The second part of this paper will give a survey of the RIM process, the chemistry of RIM polyurethane/polyurea materials, and examples of their applications.