Development and performance evaluation of wood-pulp/glass fibre hybrid composites as core materials for vacuum insulation panels

Abstract

Thermal insulation is regarded as one of the key technologies to combat ever-increasing energy consumption. An efficient method to develop innovative and cost-effective core materials for vacuum insulation panels (VIPs) is proposed. The materials are natural and sustainable wood pulp fibre doped with various amounts of glass fibre as a reinforcing phase to create a hybrid multi-level network composite core material through the conventional wet papermaking process. The basic characteristics of both wood pulp fibre and glass fibre are studied, and the effect of glass fibre on the textural properties and thermal insulation performance of the composite core materials of the VIPs is investigated. The results showed that all core materials achieved an uniform dispersion of fibres, and the axes of the fibres were randomly in the three-dimensional (3D) network structure. Upon increasing the glass fibre content, the thermal conductivity of the VIPs gradually decreased due to structural changes in the core materials. Both the pore diameter and porosity increased with the glass fibre content. The thermal insulation of the developed VIP was comparable to those of most commercial VIP products. Thermal conductivities of 6.48 and 4.69 mW/(m∙K) were obtained for the VIP with 100% wood pulp fibre and wood-pulp/glass fibre composites (50% mass ratio), respectively. Furthermore, after 365 days of storage, the composite core material with 50% glass fibre maintained a thermal conductivity of 7.42 mW/(m·K) without a getter or desiccant. Even in the accelerated aging condition after 28 days, the increase in the thermal conductivity was less than 5.00 mW/(m·K).