Investigation of various hardwood and softwood fibres for the usage in wood-fibre insulation panels

The objective of this study was to investigate the mechanical and physical properties of wood-fibre insulation panels (WFIP) from fibres of various hardwood and softwood species, which were produced in a refiner by thermo-mechanical pulping. WFIP with a raw density of 100 kg m-3 for rigid panels and 50 kg m-3 for flexible mats were manufactured using a dry process with hot-steam (rigid panels) and hot-air (flexible mats). The rigid panels were bonded by polymeric diphenylmethane diisocyanate (pMDI, 5 wt% related to the weight of the dry fibre material), and the flexible mats were bonded with 7 wt% bi-component (Bico) fibres. The study showed that hardwood fibres can in principle be used to produce WFIP for both rigid panels and flexible mats. Investigation of the fibre structure and porosity of the WFIP by computed tomography (CT) on smaller samples revealed neither correlations between porosity and bulk density of the fibres, nor between porosity and thermal conductivity, nor between porosity and mechanical properties. The physical-mechanical properties, thermal conductivity and flammability were different for the various wood species studied. Overall, WFIP made from beech showed the best properties of the hardwoods and were comparable to those made of softwoods.