The present work is a comparative study of the impact of different Alfa fiber modifications on fiber properties, as well as on polylactic acid (PLA) composites behaviors. A specific process that combines successively mechanical, chemical, and enzymatic treatments (xylanase and pectinase) was employed to optimize the performances of Alfa fibers. The treatments reduced the levels of lignin, hemicellulose, and pectin in the fibers. This reduction was associated with a rise of defibrillation degree, an increase of cellulose content and an enhancement of thermal stability, as shown with SEM observations, biochemical composition determination, FTIR measurements and thermo‐gravimetric analyzer results. Bio‐composites were fabricated using a twin‐screw extruder and an injection‐molding machine with a fiber load of 20%. Tensile, flexural and water absorption tests revealed an improvement of mechanical strengths and water resistance for the treated fibers composites, with the enzyme treatment being the most efficient. SEM analysis showed a better impregnation and distribution of enzyme treated fibers within the matrix. An improvement of the thermal properties of composites filled with Alfa treated fibers was noticed when compared with untreated fibers composites. The data indicated that the technology of enzymes can be used as a powerful and eco‐friendly approach to treat natural fibers and to increase their potential of reinforcement.

Poor interfacial adhesion between vegetable fibers and bio-based thermoplastics is recognized as a serious drawback for biocomposite materials. To be applicable for a large-scale production, one should consider appropriate methods of natural fiber handling. This study presented poly(lactic acid) (PLA) reinforced with Alfa short fibers and four types of fiber treatment were selected. The effect of these treatments on the tensile properties and the morphology of biocomposites was studied. Composite samples were produced using a twin-screw extruder and an injection molding machine with a fiber percentage of 20 wt %. Prior to composite manufacture, Alfa fibers were subjected to mechanical, chemical and enzymatic modifications. The comparison of enzyme treated fibers and NaOH treated fibers was investigated by means of biochemical and morphological analyses. It was observed that enzymes decompose lignin, pectin and hemicelluloses from the fiber bundles interface leading to the reduction of technical fiber diameter and length. The elimination of these hydrophilic components resulted also in an increase of the water resistance of treated fibers. A bigger fiber-matrix interface area was thus created, which facilitated fiber-matrix adhesion and enhanced mechanical characteristics of the composites. SEM micrographs showed homogeneous distribution of treated fibers in the polymer matrix. Tensile strength of PLA biocomposites filled with pectinase treated fibers was increased by 27% over untreated samples. The data proved that enzymatic treatment can be used as an effective and ecofriendly strategy of fiber modification for natural fiber-reinforced composite production. These materials can be used in several domains such as construction, automotive applications and packaging industries.