The Processing and Performance of High Temperature Polymers for Automotive Fluid Handling Applications

Abstract

One of the main focuses on automotive engine design in the last number of years has been a move towards engine compactness in an effort to increase cabin space. This has lead to a dramatic increase in temperature around the engine compartment from around 120dC to 200dC. This exceeds the maximum service temperature of many of the polymer materials currently used in fluid delivery systems. Already some of these components are now of necessity being replaced with metals. These metallic systems although heat resistant, are heavier, difficult to form and prone to fatigue failure. This present work investigates the melt degradation properties at elevated temperatures and the effect of immersion in standard automotive fluids (an extension of SAE J2027) on the mechanical performance of a range of polymers that are potential candidate materials for use in such “under bonnet” high temperature applications. The materials that were investigated included nylons, polypropyleneoxide/polyamide blends (PPO/PA), and polyetherimide (PEI). The rheological characteristics of nylon 4.6, PPO/PA and PEI were investigated and the results showed significant decrease in shear viscosity at dwell times in excess of three minutes for nylon 4.6, and PPO/PA. Injection moulded samples of the nylon 4.6, impact modified nylon 4.6, nylon 12, PPO/PA and PEI were immersed in the standard automotive test fluids, Fuel C, zinc chloride solution and aggressive water. Subsequent mechanical analysis of the various specimens showed only slight decrease in the tensile modulus of the nylon 4.6 after immersion in Fuel C, however significant weight gain and deterioration in tensile modulus were recorded after immersion in aggressive water. Dynamic Mechanical Thermal Analysis on the nylon 4.6 showed only slight decrease in storage modulus (Log E') and Tg, after immersion in Fuel C. However a significant decrease in Tg, by up to 80dC was recorded for samples immersed in aggressive water.