Thermal insulation materials based on eucalyptus bark fibres

Abstract

The civil construction industry significantly contributes to global energy consumption, prompting a shift towards sustainable practices to mitigate environmental impacts throughout the building lifecycle. Traditional thermal insulation materials, such as polyurethane foam and mineral wool, are cost-effective but fail to meet environmental safety standards. In this context, plant-based materials have emerged as an eco-friendly alternative for thermal insulation, with agroforestry waste offering a sustainable raw material source. This waste is abundant and often improperly disposed of, thus utilizing it can reduce the environmental footprint of the agroforestry sector. This study focuses on developing thermal insulation plates using eucalyptus bark fibres, with some samples incorporating wheat straw. Various methods were employed: sodium silicate as a binder in some samples, while others used a binder-free method involving pulping bark in lye, and some included carbonised eucalyptus bark. The primary goal was to evaluate properties like thermal conductivity and moisture sorption. The electron microscope analysis provided insights into the microstructure of the fibres, explaining their insulation mechanisms. The thermal conductivity of the plates ranged from 0.036 to 0.059 W/(m·K) at a density of 80–220 kg/m3, influenced by the preparation processes (mechanical grinding, lye pulping, carbonization) and binder use. Eucalyptus bark fibre samples demonstrated low moisture sorption for plant-based materials, with 9.4–14.5 % at 60 % relative humidity and 21.6–38.5 % at 97 % relative humidity. Additionally, the samples showed high resistance to fungal growth when wet, suggesting good durability for thermal insulation applications. Overall, the study's results indicate that eucalyptus bark fibres hold significant promise as a sustainable raw material for producing thermal insulation, offering an environmentally friendly alternative to traditional materials while enhancing the durability and effectiveness of insulation in construction.