New Thermoplastic Polyolefins are being developed targeting lower Coefficient of Linear Thermal Expansion (CLTE) properties to allow greater design flexibility for exterior automotive applications. These complex resins often contain reinforcements of various aspect ratios, in addition to multiple glass transition temperature rubbers, within a semi-crystalline Polypropylene resin matrix. A practical understanding of the material and test variables involved in the characterization of CLTE is a requirement for design engineers when assessing the dimensional stability of the resin for application feasibility. Characterization methods developed to quantify dimensional stability currently allow for flexibility in how the test procedure is executed, which can result in possible bias in measured data. This paper will review the test methods utilized to characterize the dimensional stability of Thermoplastic Polyolefin Resins, and their relationship to material variables.
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