LONDON - New developments in polyurethanes technology could reduce the cost of vehicles and make them lighter and stronger, concluded a conference organized by the Association of German Engineers.
A new process - long-fiber injection molding - is showing great potential for the automotive industry, but recent improvements in conventional techniques could also offer significant advantages.
The long-fiber injection-molding process allows fibers of up to 100mm in length to be delivered into the production mold at the same time as the foam system.
By contrast, the conventional reinforced-reaction injection-molding technique can only use glass fibers of up to 0.3mm in length, which restricts the degree of reinforcement potential, and they have to be put into the mold before the foaming system can be introduced.
The result is that polyurethanes made by the long-fiber method are stronger and, claim some manufacturers, up to 30 percent cheaper to produce.
The system has already been used in the automotive industry. German plastics manufacturer KGV has produced floor and noise-control components for trucks.
The company did experience problems initially. There were difficulties with the glass-fiber cutting instrument and unacceptable variations in the quantity of the glass. Once these were resolved, though, an in-mold time of less than 160 seconds for a wall thickness of 7mm and an overall part weight of 6.7kg was possible.
The cost in terms of original equipment, spare parts and skilled personnel with experience in robotic production methods is relatively high. But once operational, it is still cheaper than conventional methods.
The reinforced-reaction injection molding production technique has suffered from the high costs of its labor and refinishing processes, but the introduction of new materials is cutting the expense and reducing the weight of the finished products.
'The market prospects for car fenders made of reinforced polyurethane are very good,' said Hans-Joachim Meiners of plastics manufacturer Bayer AG. He believes the material is particularly suitable for large, complex body parts. Bayer's new Bayflex 180 material, coupled with thin-wall molding technology, has allowed parts with a wall thickness of only 2.5mm to be produced.
A further benefit, especially for small series producers, is that the production method requires tools made of epoxy resin rather than the much more expensive steel tools.
The production of body parts using the reinforced-reaction injection-molding method is now an acceptable alternative to steel or the sheet-molded compound PVC.