Moisture diffusion and its impact on uniaxial tensile response of biobased composites

Biobased composites made from biopolymers and plant-based fibers are being evaluated for construction applications as replacements for wood or petroleum-based composites and plastics. The biobased composites studied here have been demonstrated to rapidly biodegrade in anaerobic conditions to methane thereby reducing construction-related landfill waste and producing a useful end product, namely fuel for energy or a feedstock to grow more biopolymer. To be a useful in construction, susceptibility to moisture and eventual moisture resistance is necessary. Diffusion properties and mechanical properties are characterized in various moisture and temperature conditions for hemp/cellulose acetate and hemp/poly(β-hydroxybutyrate) composites. The composites were observed to follow Fick’s 2nd law of diffusion. The tensile moduli of elasticity were found to decrease with full moisture saturation while the ductility increased and the ultimate strength did not change significantly. Measured diffusion coefficients are compared to petroleum-based and other biobased composites.