Abstract
Phenolic foam composites (PFs) are of substantial interest due to their uniform closed-cell structure, low thermal conductivity, and good thermal insulation performance. However, their disadvantages of a high pulverization rate and poor mechanical properties restrict their application in building exterior insulation. Therefore, the toughening of these composites is necessary. In this paper, poplar fiber was treated with an acetylation reagent, and the acetylated fiber was used to prepare modified phenolic foams (FTPFs); this successfully solved the phenomenon of the destruction of the foam structure due to the agglomeration of poplar fiber in the resin substrate. The foam composites were comprehensively evaluated via the characterization of their chemical structures, surface morphologies, mechanical properties, thermal conductivities, and flame retardant properties. It was found that the compressive strength and compressive modulus of FTPF-5% respectively increased by 28.5% and 37.9% as compared with those of PF. The pulverization ratio was reduced by 32.3%, and the thermal insulation performance and flame retardant performance (LOI) were improved. Compared with other toughening methods for phenolic foam composites, the phenolic foam composites modified with surface-compatibilized poplar fiber offer a novel strategy for the value-added utilization of woody fiber, and improve the toughness and industrial viability of phenolic foam.
Highlights
Energy resources are the material basis of human survival and development, and the key to sustainable economic development
In the FTPFs, the cell density decreased with the increase of fiber content, the degree of reduction was less than that in the fiber-reinforced phenolic foam (FPF); this was due to the weakening of fiber agglomeration after acetylation modification, and the fibers had better compatibility with the resin substrate
The most outstanding and thermal flame retardant properties of phenolic resin foams, it was found that the prepared performance of the FTPFs was the foam with an acetylated fiber addition amount of 5% (FTPF-5%)
Summary
Energy resources are the material basis of human survival and development, and the key to sustainable economic development. Phenolic foam (PF), an excellent fire insulation composite, has reached the standard of Class B1 flame-retardant foam without modification [4] It has a uniform closed pore structure, low thermal conductivity, and good thermal insulation performance, and is better than PS and PU. The addition of short fibers as a reinforcing material for phenolic foam can reduce its brittleness and improve its shear strength [19]. Acetic anhydride has been used to react with the hydroxyl groups on the surface of fiber, and acetyl groups are grafted onto the surface to form an esterification layer to reduce the polarity of the fiber This is conducive to the better fusion of fibers between resins, and could avoid the large holes between foam caused by fiber agglomeration. Acetylated modified plant fibers are expected to improve the mechanical properties and reduce the fragility of phenolic foam. The chemical structures, morphological characteristics, mechanical properties, and thermal properties of PF and wood fiber-reinforced phenolic foam (FPF) were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), pore morphology analysis, mechanical properties, thermal conductivity testing, and flame retardant performance analysis (LOI)
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