Bio-Based Composite from Sunflower Stalks for Building Wall Panels

Burning sunflower stalks after harvesting could pose a significant environmental risk due to particulate matter 2.5 pollution. The use of low-cost recycled materials in building products is on trend. In this study, two distinct methods, hot oven, and hot compression, were used to form a bio-composite from sunflower stalks and bark, using natural latex as a binder. The physical, mechanical, thermal, and acoustic properties of the bio-composite were determined. The test box was used to evaluate the thermal performance of bio-composites. The bio-composites had a density of 515.67–864.24 kg/m3, similar to flat-pressed particleboards (400–900 kg/m3). The moisture content varied from 6.01 to 14.20%, with only the 1:5 and 1:6 sunflower stalk bio-composite by hot compression having a moisture content higher than 13%. Thickness swelling ranged from 5.63% to 12.03%. All composites had a fire resistance of less than 33 mm/min. As natural latex increases, the water absorption of sunflower stalks decreases while at the same time increasing fire resistance. The thermal conductivity coefficient ranged between 0.117 and 0.161 W/mK. The noise reduction coefficient (NRC) of 1:4 sunflower stalks in a hot oven and 1:6 sunflower bark in a hot compression were 0.233 and 0.241, respectively. The hot-compressed 1:6 sunflower bark bio-composite exhibited a room temperature profile that was similar to that of the MDF board. The hot compression method revealed better results in density, water absorption, flexural strength, and flexural modulus than the hot oven method.