Effects of Pyrolysis Temperature on Pore Structure, Carbon Disorder, and Thermal Transport in Rice Husk Char/PVDF Films

Low-cost, sustainable thermal insulation materials are needed for energy-efficient thermal management. Here, porous rice husk char (RHC) was produced from agricultural waste by pyrolysis at 300, 500, and 700 °C. RHC/polyvinylidene fluoride (PVDF) composite films were then prepared by blade coating where feasible. We examined how pyrolysis temperature affected char structure, carbon disorder, film morphology, and thermal transport. RHC-300-16 did not form an intact self-supporting film under the processing conditions used. RHC-700-16 contained coarser agglomerates and larger visible voids than RHC-500-16. RHC-500-16 exhibited a higher BET specific surface area (3.1347 m2·g−1) and total pore volume (0.007716 cm3·g−1) than RHC-700-16 (1.9471 m2·g−1 and 0.003153 cm3·g−1, respectively), with average BJH pore diameters of 33.30 and 21.66 nm, respectively. RHC-500-16 had a room-temperature thermal conductivity of 0.059 W·m−1·K−1. In a qualitative 100 °C heating-stage test, RHC-500-16 exhibited a lower surface temperature than a thickness-matched paper control. The measured thermal conductivity was associated with the combined effects of pore characteristics, film morphology, interparticle contacts, and carbon structure. These results link pyrolysis temperature to char structure and composite-film thermal conductivity in biomass-derived insulation films.