Composite materials based on rice straw and natural rubber for thermal insulation applications

Thermal properties of composites fabricated with coalescence of two low thermal conducting materials, rice straw and natural latex were investigated. Composites constituting various weight content of oven-dried blended rice straw mixed with a constant volume of natural latex were fabricated with a surface area of 31 cm² and their thermal properties were compared by pressurizing under a force of 5 tons. Hot Disk Thermal Constants Analyzer Transient Plane Source (TPS) 500S was used to measure the thermal properties such as thermal conductivity, volumetric specific heat capacity, and thermal diffusivity of the aforementioned composites. The lowest thermal conductivity was achieved for both the unpressurized and pressurized composites with 25% of the rice straw’s weight content, which was recorded as 0.0636 and 0.1526 Wm-1K^-1 respectively. High Specific heat capacity and less thermal diffusivity were also seen in the pressurized samples with 25% of rice straw, whereas this behaviour was the opposite in the unpressurized sample. The effect of the applied pressure on the thermal properties of the composite is also studied and it was observed that the thermal conductivity increases up to 8 tons on 31 cm² in the composite with increasing pressure and then decreases while it continues to increase in the sample made of rice straw alone. Since high specific heat and low thermal diffusivity are the desired features of a thermally insulating material other than the low thermal conductivity, this economical and eco-friendly composite pressurized up to a certain limit could be used by further processing with preservatives toward efficient energy management as a good material for thermal insulation of building applications.