Effect of blowing agent concentration on rigid polyurethane foam and the properties of foam-core particleboard

Abstract

ABSTRACT In this research, a sandwich panel with particleboard as surface layers and rigid polyurethane (PU) foam as core layers (foam-core particleboard) was produced with a one-step in situ foaming process. The effects of hydrofluorocarbon concentration as the blowing agent (BA) on the foam features and physical and mechanical properties of the produced panels were investigated. Typical micrograph of the rigid PU foam showed well-defined closed cells of spherical and polyhedral shapes. It was shown that the number of fractured cells in the foam structure was increased with the addition of BA in the amount of more than 4.5%. The results showed that the bending strength and internal bond values significantly raised with increasing BA concentration up to 6%. Screw withdrawal resistance from the face and thickness swelling were not significantly changed while the BA concentration varied. Edge screw withdrawal resistance and water absorption were drastically decreased when the blowing agent concentration was raised in the whole studied range. ABBREVIATIONS: PU: polyurethane; OH: hydroxyl; PO: polyol; ISO: isocyanate; BA: blowing agent; PMDI: polymeric methylene diphenyl diisocyanate; BS: bending strength; IB: internal bond; SWR: screw withdrawal resistance; TS: thickness swelling; WA: water absorption