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The presence of a foreign substance on or within a polymer often affects the mechanical, chemical and thermal properties of the material. The change in strength and rigidity of a polymer resulting from the plasticizing action of a sorbed chemical or due to the withdrawal of an added plasticizer by the leaching operation can seriously affect the useful life of the material. In the real engineering world, incompatible chemicals and lubricants get onto various plastic components unexpectedly through design, manufacturing processes, customers services and repairs. This paper presents a number of case-studies which illustrate how undesirable chemicals found on plastic parts can affect product performance and cause damage to the parts.

As automotive manufacturers continue to increase their use of thermoplastics for interior and exterior components, there is a likelihood of squeaks due to material contacts. To address this issue, Ford's Body Chassis NVH Squeak and Rattle Prevention Engineering Department has developed a tester that can measure friction, and any accompanying audible sound, as a function of sliding velocity, normal load, surface roughness, and environmental factors. The Ford team has been using the tester to address manufacturing plant issues and to develop a database of polymeric material pairings that will be used as a guide for current and future designs to eliminate potential noise concerns. Based upon the database, along with a physical property analysis of the various plastic (viscoelastic) materials used in the interior, we are in the process of developing an analytical model which will be a tool to predict frictional behavior.