Adhesion characteristics of plasma-treated flax fabrics and elastoplastic properties of their biocomposites

Recently, there has been growing interest in replacing synthetic fibers with natural fibers in polymer composites due to several advantages of natural fibers over synthetic ones, such as low cost, low density, sustainability, and biodegradability. However, a significant drawback of natural fibers is their high capillary water absorption, worsened by waxes and atmospheric pollutants, resulting in weak adhesion with polymer matrices. Surface treatments, including plasma treatments, have shown promise in improving this interfacial bonding. In this study, woven flax fabrics (FFs) were treated with two plasma techniques: atmospheric pressure plasma torch (APPT) and low-pressure plasma (LPP). The plasma effects on the fibers' surface, wettability, and surface energy were assessed through X-ray photoelectron spectroscopy and contact angle measurements, respectively. Subsequently, the treated fibers were utilized to fabricate biopolymer composites using polyamide1 (PA11), green low-density polyethylene (GPE), and polybutylene succinate (PBS) as matrices. The adhesion strength and elastoplastic behavior of the biocomposites were compared by peel-off test and plasticity index measurement. The results indicated that both treatments successfully improved the FFs' surface characteristics, resulting in increased wettability and surface energy. The higher peeling strengths and lower plasticity indices confirmed the improvement in the adhesion of treated FFs with the biopolymer matrices.