High frequency radar transmittance in bumper and exterior trim parts molded from thermoplastic olefins (TPOs): Part I TPO base resin

Abstract

AbstractAn extensive investigation of the interaction of thermoplastic olefin (TPO) compounds with high frequency radar wave has been conducted to understand how TPO materials affect radar sensor efficiency, an important function for vehicle safety and especially the advancement of autonomous vehicles. In this article, the effect of major ingredients of a TPO on its dielectric properties was studied, and then a wide range of TPO compounds were evaluated for their radar transmittance or attenuation. It was demonstrated that the characteristics of polypropylene (PP) resin and rubber have little impact on the dielectric properties of a TPO, thus minimal influence on TPO's radar transparency, while increasing the talc loading in the compound increases the dielectric constant of the TPO. The TPO materials containing talc from 7% up to 34% were found to have dielectric constants ranging from 2.30 to 2.70 and nearly zero dielectric loss. Experiments confirmed that parts molded with these materials are transparent to high frequency radar wave at optimized thicknesses. Some pigments for coloring the materials also affect dielectric properties of TPOs, thus radar transmittance, with metal pigments showing the most impact. Finally, commercial TPO products are shown to have great batch to batch consistency in radar transmittance at a selected part thickness.