Development and performance evaluation of cool black surface on thermoplastic polyolefins via incorporation of non-near infrared absorptive pigments

Absorption of the near-infrared (NIR) region of solar irradiance spectrum of the sunlight causes increase of the temperature of black inner parts of vehicles. The surface temperature of these parts can be decreased by reflecting or transmitting the NIR region of sunlight. This study intends to decrease the temperature of black surfaces that are exposed to sunlight and create cool black surfaces by preventing the absorption of the NIR region of the solar irradiance spectrum. Incorporation of cool black pigments having NIR reflective or NIR transparent properties into thermoplastic olefins (TPOs) was studied. A series of compounds were generated containing only NIR reflective pigment (REF), only NIR transparent pigment (TRANS) and the mixture of these two pigments in specific loading levels. The surface temperature of black TPO compounds were compared to the TPO compounds containing conventional pigments. Results showed that an optimum TPO compound having cool black surface was obtained with the sample MIX-5 (2% REF + 0.4% TRANS) which demonstrated 28.2% cooling compared to samples with carbon black, 9.04 MPa tensile strength, 1200% elongation at break and mold shrinkage values of 0.61% and 0.11% at directions parallel and perpendicular to flow respectively.