Thermal and hygrometric performances, and mold growth resistance, of novel bio-stitched insulating fiberboards made from date and Washingtonia palm surface fibers

Abstract

This paper evaluates the performance of a novel bio-stitched, lightweight insulating fiberboards made from Phoenix dactylifera L. and Washingtonia filifera palm fiber waste. These materials are binder-free, rendering them fully biodegradable. In this study, measurements are made of water sorption and its impact on density and thermal conductivity. Both materials exhibited insulating properties, with thermal conductivity values ranging from 0.043 to 0.063 W.m⁻¹.K⁻¹ depending on density. The bio-stitched fiberboards achieved their lowest thermal conductivity at an optimum density of 85–105 kg.m⁻³. The results indicate also that the thermal conductivity and density of bio-stitched fiberboards increase significantly with volumetric water content. However, even at saturation, they retain competitive thermal insulation properties. The residual fibers used were subjected to different natural weathering durations. Three types of fiber were therefore evaluated: one fresh, one moderately weathered and the other extremely weathered, in an attempt to compare the hygrothermal properties of the elaborated fiberboards as a function of fiber conditioning. It was found that Washingtonia palm surface fiberboards have higher water absorption compared to weathered date palm surface fiberboards. In addition, mold growth was evaluated by exposing the fiberboards to severe relative humidity conditions, i.e., 74 % RH, 77 % RH, 86 % RH, and 94 % RH at 29ºC. It was observed that the proliferation of mold was slow, particularly on weathered fiberboards, while it remained moderate on the surface of fresh Washingtonia palm surface fiberboards.