Lab-scale structural insulated panels with lignin-incorporated rigid polyurethane foams as core

Abstract

Lab-scale structural insulated panels (SIPs), using lignin-incorporated rigid polyurethane (RPU) foams as the thermal insulation core, were fabricated and characterized. The RPU foams incorporating surface-modified lignin were sandwiched between two oriented strand board (OSB) sheets to produce lignin-incorporated SIPs with nominal dimensions of 350 × 350 × 46 mm3. In comparison to the reference RPU foam without lignin, the lignin-incorporated RPU foams exhibited progressively higher thermal stabilities coinciding with lignin amount, but similar thermal conductivity (˜24.5 mW·m−1 K−1) and water absorption (˜0.018 g/cm3). The bonding, shear, and flexural strength of lignin-incorporated SIPs were 150–210 kPa, 110–150 kPa, and 3–4 MPa, respectively, which were similar to that of reference (no lignin control) SIP. Lignin-incorporated RPU foams and SIPs with 5%–15% lignin addition amount exhibit better performance than the reference RPU foam and SIP. We attribute overall enhancements in thermal and mechanical properties of the lignin-incorporated RPU foams, and the corresponding SIPs, to the surface-modified lignin, serving as a reactive crosslinker with ample chemical interaction to polyisocyanates during the formation of RPU foams.