Effect of Brown-Rotted Spruce as Lignin-Enriched Filler on the Properties of Reinforced Polyurethane Foam

The study investigated the effect of lignocellulosic biomass filler decayed by brown-rot fungi on the preparation and properties of polyurethane (PU) foam. The properties of brown-rotted spruce were characterized by microstructure, chemical composition, and hydroxyl value to examine the possibility of preparing polyurethane foam using brown-rotted spruce as filler. Brown-rotted spruce was a homogeneous material, mainly composed of lignin (80.36%) with a high content (284.5 mg KOH/g) of hydroxyl groups in structure that could participate in a chain reaction with isocyanate groups on the foaming process. In the study, PU foams were prepared successfully with the addition of brown-rotted spruce as filler in different concentrations (1–10 wt%). The results showed that the addition of brown-rotted spruce improved the physical properties (low density, low thermal conductivity, high water absorption) of PU foam. These properties showed a significant dependence on filler amount. The density decreased from 89.64 kg m −3 to 60.22 kg m −3 as the filler amount increased. Scanning electron microscope showed the cellular structure of PU foam was affected by the filler amount. PU foam with low addition amount (5 wt%) had homogeneous shapes and smaller cell shapes, resulting in the highest compressive strength (0.42 Mpa). Utilizing brown-rotted wood as a lignin-enriched filler is a simple and feasible way to improve the properties of PU foam. Graphical Abstract