Form-stable bitumen/paraffin-wax/polymer binders for energy-efficient building applications

Abstract

Novel form-stable bitumen/paraffin-wax/polymer binders were successfully manufactured to be applied as energy-efficient building materials with advanced thermal energy storage and thermoregulation features. These roofing materials are composed of bitumen (B), styrene butadiene styrene copolymer (SBS), and paraffin wax (PW) as phase change material (PCM) for thermal energy storage applications. Systems with a fixed weight ratio B/SBS = 7.33 and PW concentration ranging from 0 to 70 wt% were prepared. Then, thermal stability, microstructure, rheological properties, technological and leakproof performance tests were performed on these binders to assess the optimal compositions. After that, a comprehensive thermal energy storage characterization was conducted on the selected prototypes and, finally, the temperature regulation performance was studied by using simulated solar irradiation. All materials show excellent thermal stability no matter PW concentration used, whereas the rheological properties improve as PW content in blends increases. However, softening temperature requirements, specified by ASTM D8051, limited PW concentration to 30 wt%. Interestingly, no liquid PW leakage from bituminous matrix was found for such a concentration, which has a high heat storage capacity (ca. 60 J/g) and suitable thermal properties (e.g. thermal conductivity and specific heat capacity). As a result, material exhibits a complex solar and thermal behaviour that yields a Latent Heat Thermoregulation Index (LHTI) value greater than for other efficient energy building materials.