Lignin-Based Phenolic Foam Reinforced by Poplar Fiber and Isocyanate-Terminated Polyurethane Prepolymer

Abstract

Phenolic foams (PFs) are lightweight (<200 kg/m3), high-quality, and inexpensive thermal insulation materials whose heat and fire resistance are much better than those of foam plastics such as polyurethane and polystyrene. They are especially suitable for use as insulation in chemical, petroleum, construction, and other fields that are prone to fires. However, PFs have poor mechanical properties, poor abrasion resistance, and easy pulverization. In this paper, a polyurethane prepolymer was treated with an isocyanate, and then the isocyanate-terminated polyurethane prepolymer and poplar powder were used to prepare modified lignin-based phenolic foams (PUPFs), which improved the abrasion resistance and decreased the pulverization of the foam. The foam composites were comprehensively evaluated by characterizing their chemical structures, surface morphologies, mechanical properties, thermal conductivities, and flame-retardant properties. The pulverization ratio was reduced by 43.5%, and the thermal insulation performance and flame-retardancy (LOI) were improved. Compared with other methods to obtain lignin-based phenolic foam composites with anti-pulverization and flame-retardant properties, the hybrid reinforcement of foam composites with an isocyanate-terminated polyurethane prepolymer and poplar powder offers a novel strategy for an environmentally friendly alternative to the use of woody fibers.

Formaldehyde Free Renewable Thermosetting Foam Based on Biomass Tannin with a Lignin Additive

“…During the curing process of the mixture, bubbles were generated in the cured mixture, forming a stable network structure. The formation of foam can be divided into three basic processes: bubble nucleation, bubble growth, and foam curing [25,26]. The stage of bubble nucleation is the key step for formation of high quality foam.…”

“…Foams, such as polyurethane, polystyrene, phenolic, and polyethylene, have been widely used in building, packaging, automobile, and other fields due to their excellent thermal insulation, sound resistance and cushioning properties [1][2][3][4]. However, these foams are synthesized with non-renewable raw materials and contain toxic substances, which limit their future development.…”

Recent developments in lignin modification and its application in lignin‐based green composites: A review

“…Dispersing The devolatilization ratio was reduced by 43.5%, and the thermal insulation and flame-retardancy of the material were both improved [74] Abbreviations: PU, polyurethane.…”

Progress in Bio‐Based Phenolic Foams: Synthesis, Properties, and Applications

“…Chen et al [94] developed isocyanate-terminated polyurethane prepolymer and poplar powder-modified lignin-based phenolic foams to improve the compressive strength and reduce the pulverization of the foam. The compressive strength increased from 119.6 to 125.13 kPa and its pulverization rate declined from 7.7 % to 5.2 % with 5 % polyurethane modification.…”