An experimental evaluation of a new eco-friendly insulating material based on date palm fibers and polystyrene

The purpose of this study is to minimize the environmental impact and to reduce the cost of petroleum-derived polystyrene by the use of date palm leaves remnants in the production of poly- styrene/date palm fiber composite materials (PS-DPF). Moreover, this new material must have mechanical properties and thermal insulation comparable or superior to those of virgin polystyrene (VPS) or other insulating materials. Three types of fibers are used to make samples with fillers of 10%, 20%, and 30% (by weight), namely untreated fiber (UDPF), fiber treated by alkalinisation (ADPF), and fiber treated by benzoylation (BDPF). The melt-mixing method and hot compression molding were used for the production of the composites. Various morphological, mechanical, and thermophysical tests were carried out on the produced composites. From scanning electron mi- croscopy (SEM) micrographs, it was determined that the dispersion of filler and its interfacial in- teractions with the matrix were improved due to a reduction in the OH group present on the fibers, as validated by the Fourier transform infrared spectroscopy analysis (FTIR). X-ray diffraction (XRD) studies indicate that ADPF has the highest crystallinity index. The PS-DPF composites exhibited satisfactory tensile strength within the range of 14–27 MPa, flexural strength within the range of 31–44 MPa, and tensile and flexural modulus within the range of (2.9–5.9 GPa). The results revealed that alkaline and benzoylated treatment treatments increase the tensile and flexural strength while slightly decreasing the tensile and flexural modulus. Both chemical treatments demonstrated a similar impact on these attributes. Thermogravimetric analysis (TGA) results indicated that samples of PS filled with 30% untreated and treated fibers have the maximum thermal stability compared to VPS, with a slight advantage for the untreated sample when residues are taken into account. The thermal conductivity (λ) of the composites produced was low (0.118–0.141 W/m.K) at 18◦C, and its variation was incompatible with the bulk density (ρ), which varied from 860 to 980 kg/m3, and decreased with the incorporation of fibers. Moreover, replacing one-third of the composition of conventional building materials with a PS-DPF composite has shown promise for applications such as thermal insulation, with a reduction in thermal conductivity of up to 50%. The composite ma- terials created have revealed their potential application as thermal insulators, which encourages the frequent exploitation of waste in date-producing countries.