Published May 2003
Sustainability of a healthy global environment has become one of many priorities for the automotive industry today, and weight reduction is an important factor if the challenges of lower exhaust emissions, fuel efficiency, materials recyclability, and use of alternative automotive power and material sources are to met. Use of lighter materials in automotive body materials has long been a changing and ongoing effort. Polyurethanes have much to offer in all respects because a wide range of automotive components of varying physical properties can be produced from a single line of materials.
For example, one possibility is the further development of conventional polyurethane systems to produce automotive body panels for doors, trunks, hoods, and roofs for lightweight cars of the future more efficiently. Another possibility is to incorporate the use of biopolymers and/or natural fiber reinforcement materials in new polyurethane systems formulations with the ultimate goal of developing a biodegradable composite to improve recyclability. The status of both of these efforts is reviewed herein, as an update of this subject contained in our last "Polyurethanes" PEP Report 10C, issued in 1991.
It has been a long-standing goal for plastics engineers to produce these types of parts from reinforced polyurethane materials. However, these parts must be light weight, have good mechanical strength, improved elastic recovery, and scratch resistance, as well as good mold flow and surface smoothness.
With the latest technology, polyurethane materials can match steel panels. Apart from surmounting such hurdles as strength, stiffness, and Class A finish, polyurethane panels made with modified conventional system formulations have now largely conquered the cost problem. These new developments in polyurethane reinforced reaction injection molding (RRIM) may offer an attractive alternative to steel or polyester SMC for automotive body panels. Our conceptual estimates show that with the use of improved conventional systems formulations, the production cost of a typical automotive body panel produced by RRIM has been reduced from 412.03¢/lb to 344.98¢/lb. In addition, product properties including strength stiffness, heat resistance, and finish have been improved.