Behavior of the Flexural Strength of Hemp/Polypropylene Composites: Evaluation of the Intrinsic Flexural Strength of Untreated Hemp Strands

VALLEJOS, MARÍA E.; AGUADO, ROBERTO J.; MORCILLO-MARTÍN, RAMÓN; MÉNDEZ, JOSÉ A.; VILASECA, FABIOLA; TARRÉS, QUIM; MUTJÉ, PERE

Polymers

MDPI AG

Año: 2023 vol. 15 p. 1 - 14

The growingdemand for plant fiber-reinforced composites offers new opportunities tocompete against glass fiber (GF)-reinforced composites, but their performancemust be assessed, revised, and improved as much as possible. This work reportson the production and the flexural strength of composites from polypropylene(PP) and hemp strands (20–50 wt.%), using maleic anhydride-grafted PP (MAPP) asa compatibilizer. A computational assessment of the reaction between celluloseand MAPP suggested the formation of only one ester bond per maleic anhydrideunit as the most stable product. We determined the most favorable MAPP dosageto be 0.06 g per gram of fiber. The maximum enhancement in flexural strengththat was attained with this proportion of MAPP was 148%, corresponding to themaximum fiber load. The modified rule of mixtures and the assumption of similarcoupling factors for tensile and flexural strength allowed us to estimate theintrinsic flexural strength of hemp strands as 953 ± 116 MPa. While falling shortof the values for sized GF (2415 MPa), the reinforcement efficiency parameterof the natural fibers (0.209) was found to be higher than that of GF (0.045).