Ricerc@Sapienza

The Achilles heel of thermoplastic natural fibre composites is their limited durability. The
environmental degradation of the mechanical properties of hemp and hemp/basalt hybridreinforced
high-density polyethylene (HDPE) composites has been investigated with a special focus
on the effects of water ageing and accelerated ageing, including hygrothermal and UV radiation.
Modification of the matrix was carried out using a maleic anhydride high-density polyethylene
copolymer (MAPE) as a compatibilizer. Hybridization of hemp fibres with basalt fibres and the
incorporation of MAPE were found to significantly decrease the water uptake (up to 75%) and
increase the retention of mechanical properties after accelerated ageing. Secondary crystallization
phenomena occurring in the composites, as confirmed by differential scanning calorimetry (DSC)
analysis, were able to counteract the severe combined effects of hygrothermal stress and UV
radiation, with the exception of hemp-fibre composites where permanent damage to the fibres
occurred, with 2% and 20% reduction in tensile strength and modulus, respectively, for a 30 wt %
hemp fibre-reinforced HDPE.