SPE Library

This briefing on trends in automotive plastics will delineate the differences in plastics application areas between North American and overseas markets. The key themes addressed include: • Although mass savings are widely thought to be a key driver in metal replacement by plastics, increasingly automakers are more interested in the contribution of plastics to styling, occupant safety and comfort, and functionality. • Plastics are increasingly specified for their design freedom. They make possible the consolidation of parts and consolidation of functions, minimizing manufacturing costs while maximizing function and value. • Competition among automotive plastics is relentless and intensifying, resulting in improved forecasted growth for some plastics at the expense of others. • Plastics application trends will be compared between North America and overseas in four sectors: Interiors, Exteriors, Under the Hood, and Chassis and Powertrain. • Greater attention is being given to polymer composites in the U. S. for exterior body panels and some structural applications, with minimal interest in other countries. • Finally, more progress is being made in the recycling of plastic manufacturing scrap than in the recycling of plastic parts/materials from scrap vehicles. This is so because manufacturers have control over process scrap, which improves recyclability and the value of recycled materials. The use of plastics in vehicles is steadily increasing. This trend is expected to continue. On average, current vehicles use about 113 Kg (250 Lbs) of plastics and that amount is estimated to grow to 137 kg (300 Lbs) per vehicle in the next ten years. Historically, vehicle weight savings has been a primary driver in replacing metals with plastics on vehicles. However, today styling, end-use functionality, and better manufacturing economics through parts consolidation are the key factors in choosing plastics to replace other materials in vehicle applications. In addition, fut

This paper shows how air or nitrogen can be used to impart vibration and/or pressure pulses to a melt. Air is already used to blow preforms and parisons [1] inside of molds, and to core out hollow articles in the process of Gas Assist Injection Molding [2]. The methods of gas assist molding have demonstrated their great usefulness in injection molding not only to hollow parts out but also to induce an excellent surface finish. Melt vibration techniques have also been reviewed [3,4] and show great potential to reduce viscosity during filling and impart optical and mechanical benefits, i.e. stiffness, strength and clarity, without resorting to processing aids such as thinning or nucleating agents. The present paper explores the processing of injection molded plastics under gas vibration. Vibrated gas can be used for several purposes. 1. Gas can be inserted and vibrated in the mold prior to melt injection to modify the filling process mechanism, fuse knit lines, heal sink lines and other defects due to flow imperfections. 2. Compressed Vibrated Gas can act like a pressurized vibrated gas spring, which helps induce orientation benefits in the short shot during filling completion. 3. Vibrated air pressure, localized in specifically designed air-runners distributed around the runners and inside the mold, helps fill and pack the mold, core out hollow parts and balance flow in multi-cavity molds. 4. Vibrated Gas can also be used to tag parts for recognition during recycling or later inspection. The paper reviews hardware and controls requirements to apply this novel technique to injection molding.