Environment Friendly, Renewable and Sustainable Natural Fiber‐Reinforced Polylactic Acid ( PLA ) Composites

ABSTRACT Polylactic acid (PLA)/plant fiber composites have attracted increasing interest as sustainable alternatives to petroleum‐based plastics due to their renewability, biodegradability, and environmental compatibility. However, the inherent polarity mismatch between hydrophilic plant fibers and the hydrophobic PLA matrix often results in weak interfacial adhesion, poor compatibility, and fiber agglomeration. This review provides an overview of recent developments in PLA composites reinforced with bast fibers (hemp, flax, ramie), bamboo fibers, and wood fibers. Particular attention is given to interfacial modification strategies—including alkali treatment, silane coupling, acetylation, aerogel, and bio‐inspired coatings—and their effects on interfacial bonding, mechanical strength, moisture resistance, UV stability, and flame retardancy. Studies have demonstrated that optimizing processing parameters such as fiber content (20–50 wt%), treatment concentration, reaction temperature, and melt‐blending conditions significantly improves interfacial compatibility and stress transfer efficiency. Recent research also highlights that synergistic modification approaches, such as combined alkali–silane treatment and nano‐filler incorporation, can effectively enhance mechanical performance while maintaining biodegradability. Overall, interfacial engineering and process optimization are identified as the key pathways to achieving high‐performance and eco‐sustainable PLA/plant fiber composites, paving the way for their broader application in packaging, automotive, and biomedical fields.