Lignin-Based Rigid Polyurethane Foam Reinforced with Pulp Fiber: Synthesis and Characterization

Abstract

Petroleum-based polyol was replaced with different amounts of lignin (8.33−37.19% w/w) to prepare lignin-based rigid polyurethane foam (LRPF). The LRPF containing 37.19% lignin was further reinforced with different weight ratios (1, 2, and 5 wt %) of pulp fiber. The resulting foams were evaluated by their chemical structure, cellular structure, density, compressive strength, and thermal property. Fourier transform infrared (FT-IR) and 13 C CP/MAS NMR spectra indicated that typical urethane linkages in LRPF were formed. Scanning electron microscope (SEM) results showed that the cell shape is significantly affected by the lignin and pulp fiber contents, which resulted in inhomogeneous, irregular, and large cell shapes and further decreased the densities of the LRPF. Mechanical results suggested that the compressive strength of the LRPF decreased with the increase in lignin content, but the additional pulp fiber had no significant effect on the compressive strength. Thermogravimetric analysis results demonstrated that the introduction of lignin led to high "carbon residue", but the introduction of pulp fiber would slightly improve the thermal stability of the LRPF.

Characterization of Biobased Polyurethane Foams Employing Lignin Fractionated from Microwave Liquefied Switchgrass

“…The result revealed that the addition of 15% lignin into the PU matrix had a significant effect on the foam cellular structures. The alteration in the cell structure may be due to the fact that high lignin content affected the cell nucleation process in the preparation of PU foams [30]. Similar results were also found by Pan and Saddler [17], who reported that the increase of ethanol organosolv lignin ratio in petroleum-based polyol resulted in particularly large cells (bubbles).…”

“…However, lignin was not reinforcement filler in the foam in the report of Xue et al [30], who argued that lignin was not completely miscible with the polyol, and the uneven mixture of lignin and polyol resulted in irregular cellular structure and thus weakened the mechanical properties. According to other researches [33,34], the addition of 2 wt% and 1.5 wt% cellulose and wood flour into foams increased the compressive strength by 21% and 30%, respectively.…”

Biopolyols obtained via microwave-assisted liquefaction of lignin: structure, rheological, physical and thermal properties

“…Due to the incorporation of bio-based polyol, the cellular shape became more inhomogeneous and less regular. This was probably because the biopolyol with lignin did not disperse well in the PU foam (Xue et al 2014). Table 5 shows other parameters describing the cellular structure of the analyzed materials that have been calculated on the basis of microscopic images in Fig.…”

Bio polyetherurethane composites with high content of natural ingredients: hydroxylated soybean oil based polyol, bio glycol and microcrystalline cellulose

“…they are a sustainable material commonly present in nature, characterized by low relative density, high strength and rigidity, and relatively low cost Alamri et al 2012;Datta and Glowinska 2011;Kiziltas et al 2011;Magnus et al 2007;Avérous and Le Digabel 2006). Moreover, from among wood-derived raw materials, lignin can be used in the production of polyurethanes as liquid polyol component instead of commercial polyols (Xue et al 2014;Li et al 2012). The methods for obtaining polyester polyols by using lignin originating from hard and soft wood, and recycled paper have been described in the published literature.…”