Enhancing the cooling properties of low-density polyethylene films by combining near-infrared reflective additives

In the last years, the rising temperature caused by global warming brought the research to find new efficient solutions to lower the temperature of buildings and reduce the consumption of electrical energy for air conditioning. In this work, we propose the combined use of organic and inorganic near-infrared (NIR) reflective additives in low-density polyethylene (PE) films as an accessible plastic coating with enhanced cooling features. Two 'cool' pigments, the inorganic Sicopal (R) Black (Si Black) and the organic Paliogen (R) Black (Pa Black), were investigated for black-tinted coatings, while TiO2 (TI) and glass bubbles (GB) were tested for opaque white coatings. The additive's size and concentration influence the composite processing, and their ultimate optical properties were determined in terms of total solar reflectance (TSR) and cooling effect under solar radiation. TI and GB dispersed in PE showed the highest TSR, whereas the organic Pa Black confirmed its superior reflective features with respect to the traditional carbon black (CB). Moreover, a significant increase in the TSR occurred when TI or GB was added to the black pigments (12.7% and 13.6%, respectively). TSR increasing led to a cooler black-tinted PE film under solar irradiation. When using reflective pigments, a cooling effect of about 10 degrees C was measured with respect to the traditional CB.