Environmental performance of kenaf-fiber reinforced polyurethane: a life cycle assessment approach

Outstanding mechanical, thermal and environmental properties of kenaf, as well as successful applications of kenaf-based boards in structural insulated panels (SIPs), inspired the authors to investigate the incorporation of kenaf core in the polyurethane insulation core of SIPs to create environmentally friendly building material. Three composites made of rigid polyurethane (PU) reinforced with 5, 10 and 15 percent kenaf core were prepared and analyzed. The three composites and pure rigid polyurethane were then used as insulation cores of SIPs with the same kenaf-based structural boards. A life cycle assessment (LCA) was conducted to determine the environmental profiles of the four SIPs in 10 and 50° Celsius. It is shown that although kenaf has much less environmental impact than PU, increasing the amount of kenaf core in PU composites does not necessarily result in less environmental impact. In fact with the current practice of making the composites, kenaf core does not replace the PU; instead, it mostly fills the void space, which is initially filled with air and, hence, the kenaf core decreases the porosity of PU composites and increases the density without improving thermal resistance. Structural adequacy of the samples was also examined based on the ASTM C393-00 “three point flexural test”. Results show that the more the kenaf loading, the less porous the composites and hence the higher shear resistance. These findings suggest that fabrication methods are critical to maintain optimal thermal and structural characteristics of composites without scarifying their environmental performance.