On filtration and heat insulation properties of foam formed cellulose based materials

Abstract

Novel biodegradable, low-density porous materials based on wood fibres are produced in foam laid media called foam-paper. Applications of foam-paper are studied in sub-micron aerosol filtration and heat insulation. The effect of foam air-content and fibre type on the variation of final product properties is determined. In the first study, the effect of fibre morphology and crowding number are investigated on the major filtration parameters such as pressure-drop, air-permeability and filtration-efficiency. The results show that increasing fibre specific surface and crowding number and decreasing pulp freeness leads to increasing both filtration efficiency and pressure-drop of foam-papers. Different combinations of additives and two methods of drying are applied in order to optimize filtration characteristics. The best filtration properties are obtained using air-dried samples with 10% and 30% weight ratio of Northern Bleached Softwood Kraft (NBSK) valley beaten fibres and freeze-dried Nanofibrillated Lyocell Fibres at high air-contents. In the second study, variations of thermal conductivity of standard foam-papers with respect to foam air-content are investigated. The results of foam-papers at higher air-contents are comparable with the results of commercial heat insulators.