Effect of Fiber Content on Sound Absorption, Thermal Conductivity, and Compression Strength of Straw Fiber-filled Rigid Polyurethane Foams

Abstract

Rigid polyurethane (PUR) foam is one of the most important insulating materials used today in the construction industry and is the main insulation material used in the global appliances industry. This study developed rice straw fiber-filled PUF (RPUF) and wheat straw fiber-filled PUF (WPUF) and explored the morphology, sound absorption properties, heat transfer, and compressive strength of the PUF composites. The results indicated that, with the higher fiber content, more open cells were observed in SEM images of the composites. The average sound absorption coefficients (ASAC) of both WPUF and RPUF were significantly increased when 5 per hundred polyols (php) by weight and 10 php fiber contents were added. When fiber contents of 15 php and 20 php were utilized, ASAC reduced due to the tortuosity of cells and large holes in the foam. The sound absorption coefficient (SAC) first increased, then decreased, and increased finally as the sound frequency increased from 100 to 2000 Hz for the two composites. The thermal conductivities of both WPUF and RPUF first decreased and then increased as the fiber content increased from 0 to 20 php. When 5 and 10 php straw contents was added, the thermal conductivities were reduced by 25% to 50% compared to that of the pure PU form (0 php), indicating that the improved thermal insulation ability was obtained. The composite compressive strength was reduced by 19% to 28% due to the fiber addition.

Waste Wood Particles from Primary Wood Processing as a Filler of Insulation PUR Foams

“…It should be noted that even with the maximum concentration of wood particles used in the tests (i.e., 20%), the value of the thermal conductivity coefficient was at a level comparable to that of pure PUR foam. Similar observations were made by Tao et al [34]. The authors noted a decrease in the value of the coefficient λ by as much as 50%, while higher amount of lignocellulosic fibers (up to 20 php) resulted in a gradual increase in thermal conductivity to a level exceeding that of pure PUR foam.…”

“…The wood particles were added to the foam at the concentrations of 0, 5, 10, 15 and 20% determined according to a weight ratio. The amount of filler was determined based on preliminary studies and a literature review on the manufacture of biocomposite PUR foams [6,17,34,35].…”

A novel hybrid polyurethane composites with ZnO particles and sheath palm residues: Synergistic effect

“…While lower contents showed a more homogeneous distribution, higher fiber levels (15 and 20 wt%) present larger agglomerates and particulates. Fibers addition formed more irregular cells, with smaller sizes and greater interconnectivity [13,26]. The cells' asymmetry results from the cell's irregular growth from the fibers, which act as nucleation points [27].…”

Alfa fiber-polyurethane composite as a thermal and acoustic insulation material for building applications

“…The results can be explained by the increase of the frictional resistance between the sound waves and the alfa fibers [58,59], composites leads to a great energy dispersal of the sound waves, a second factor is the irregular structure of the composite compared to the polyurethane matrix, the porosity of the fiber bundle and it distribution in composites increase the sound absorption capabilities. When the acoustic wave is incident onto the surface of porous structure of composites, considerable part of the acoustic energy can be converted into heat energy thus increase noise reduction efficiency [60]. The values of sound absorption coefficient vary between 0.05 and 0.35.…”