Effect of incorporation of lignin as bio-polyol on the performance of rigid lightweight wood–polyurethane composite foams

Abstract

Density reduction has become a topical issue in wood composite materials for application in building and furniture. In this study, lightweight wood-polyurethane (W-PU) composite foams with the addition of 30 wt% wood particles were prepared. Industrial kraft lignin was used as bio-polyol to substitute partial petroleum-based diethylene glycol (DEG) to synthesize rigid W-PU foams. The effect of varying lignin contents (5, 10, 15 and 20 wt% based on DEG mass) on the reactivity, morphology, density, compressive properties, water absorption and thermal stability of the foams was evaluated. Fourier transform infrared (FTIR) analysis confirmed the formation of characteristic urethane linkages in all the foam samples. With the incorporation of lignin, the foam cellular shape became irregular with formation of large cells. W-PU foams exhibited poor cellular structures with a larger number of open cells. The density of W-PU foams increased from 47 to 96 kg/m 3 as the lignin content increased from 0 to 20%. Although the foam reactivity was decreased by the incorporation of lignin, both the compressive strength and modulus were increased upon the incorporation of lignin. Furthermore, the specific compressive strength and modulus of W-PU foams increased by 55% and 48% with lignin content increasing from 0 to 20%, and the 20-day water absorption decreased by 38%. Thermal gravimetric analysis showed that the incorporation of lignin did not significantly affect the thermal degradation behaviour of foam, but it rather increased the mass of char residue. This study provides a promising method for value-added utilization of technical lignin in W-PU lightweight composites.

Highly Insulative PEG-Grafted Cellulose Polyurethane Foams—From Synthesis to Application Properties

“…Leszczyńska et al [ 51 ] showed that composites with nut shell were characterized by increased structure anisotropy and higher contents of the irregularly shaped pores than those of the reference sample. Lu et al [ 52 ] investigated PUR samples with up to a 20 wt% volume of wood or lignin. The usage of each filler resulted in the formation of poorer cellular structures, with large numbers of open cells, affecting the final properties of the composite.…”

Preparation of Polyurethane Adhesives from Crude and Purified Liquefied Wood Sawdust

“…This might be due to the intensified decomposition of urethane bonds and decomposition of soft segments, i.e., polyols [ 85 ]. The formulations with high NCO:OH molar ratios showed T max3 at a temperature over 450 °C, which referred to the degradation of hard segments, such as pMDI and aromatic lignin moieties [ 86 ]. The thermal stability of cured PU adhesives was improved considerably by increasing the NCO:OH molar ratio in both CLW- or PLW-based formulations.…”

An Efficient Catalyst Derived from Carboxylated Lignin-Anchored Iron Nanoparticle Compounds for Carbon Monoxide Hydrogenation Application

“…The intensities of FT-IR peaks corresponding to C-O stretch (1150 cm –1 , H units), C-O stretch (1263 cm –1 , G units), and syringyl C-O stretch (1360 cm –1 ) are significantly stronger than those of the original lignin. 39 , 40 Furthermore, the strong peak around 1718 cm –1 indicated a band of carboxyl stretching vibrations, 41 indicating that modified lignin contains carboxyl functional groups.…”