Toward sustainable insulation materials: Properties of hemp fiber-based composites

Abstract

Hemp-based insulators panels were developed by blending alkalinized hemp fibers with 30 wt% low-melting sheath-core polyester fibers using a carding process, followed by compression molding into a five-layer sandwich-structured insulator. The mechanical, structural, and thermal properties of the hemp/polyester composite fabric were systematically investigated through tensile testing, scanning electron microscopy (SEM), X-ray diffraction (XRD), water absorption, and thermal conductivity measurements. The hemp composite fabric exhibited a maximum tensile strength of 732.9 cN/cm 2 after thermal bonding at 140 °C for 30 min, while the highest elongation at break (85.6%) occurred at 140 °C for 10 min. The tensile strength of the insulation panels also increased with prolonged heating at 140 °C. XRD indicated a partial transformation from cellulose I to cellulose II following alkali treatment and thermal processing whereas SEM revealed thermally bonded regions formed by the low-melting polyester fibers within the nonwoven structure. The lowest thermal conductivity (0.018 W/m·K) and a corresponding to a thermal resistivity (R-value) of 1.11 K·m/W were obtained for the thermal bonding processed at 130 °C for 30 min. Water absorption increased after polyester incorporation, which was attributed to the porous architecture of the thermally bonded nonwoven composite and the partial exposure of hydrophilic hemp fibers. These findings demonstrate that hemp-polyester composites have considerable potential as lightweight, sustainable thermal insulation materials for energy-efficient building applications.