In this investigation, hemp fibers were-surface treated by ethylene polymerization grafting to determine the effect of high grafting level on the mechanical (tensile and impact) and dynamic mechanical properties of linear mediumdensity polyethylene (L) composites (20%wt.) produced via melt compounding.The results showed that, comparing the treated hemp composite (L20PH) with the untreated hemp composite (L20H), the modification reduced by 44% the modified fibers composite water absorption, while increasing the elongation and tensile strength by about 197% and 14%, respectively. Moreover, due to better interfacial interactions with the matrix and the flexibility imparted by the presence of both grafted and ungrafted polyethylene (PE) onto modified hemp fibers, the corresponding composite exhibited lower density and significantly high impact resistance (about 57%) compared to the untreated hemp composite. These results were confirmed by the composites creep strain as L20PH and L maximum strain (ε max ) was respectively 18% and 42% higher compared to that of L20H, showing that L20H has the high modulus followed by L20PH and then L. The significant improvement of the modified composite flexibility, impact resistance and the limited reduction of its modulus make this material not only suitable for building and construction applications, but also in the production of packaging and automotive parts.

This investigation proposes a natural fiber surface modification approach based on the use of a system of coupling agents (CAs) to improve the mechanical properties of polymer composites made of flax fibers and low‐density polyethylene. This system combines the coating of the NaOH treated (mercerized) flax fibers by a CA (Epolene C18 [M‐C18]) in a solution under moderated heat (70°C–80°C), followed by the addition of 1% or 3% wt. of another CA (Epolene E43 [M‐E43]) during the injection molding. The comparison between the solution modified and the neat and mercerized flax fibers using scanning electron micrograph (SEM), thermogravimetric analysis (TGA), and density underscored some differences ascribed to the presence of M‐C18 onto the modified fibers. The mechanical properties showed that the combination of solution modification and direct introduction during the injection‐molding step of 1% of M‐E43 was efficient as the corresponding composites exhibited an improvement of 9.1%, 15.9%, and 11.1% of his tensile, flexural, and impact strengths respectively compared to the neat fiber composite. Due to their good impact and flexural strengths, these composites can be suitable for automotive parts such as keyboard.