Two Step Chemical Treatment on Flax Fibers for Enhanced Interfacial Adhesion and Moisture Repulsion

Due to their reversible and sustainable properties, natural fiber thermoplastic composites are gaining popularity. The widespread use of natural fibers as reinforcements in structural components is hindered by their moisture adsorption and poor mechanical properties. In this investigation, alkaline treated and untreated flax-based high-density polyethylene (HDPE) composites were manufactured and exposed to accelerated weathering tests in accordance with ASTM G154-23, to examine their moisture absorption behavior and rate of degradation. The tensile strength of alkaline-treated samples increased by 36 percent prior to accelerated ageing, but the elastic modulus and strain to failure remain unchanged. The post-ageing tests estimated a small increase in the fracture energy of the alkaline treated samples. However, no significant difference was obtained in elastic modulus, tensile strength and strain to failure. Further, the elastic modulus of both treated and untreated samples increased due to embrittlement, which shows the ineffectiveness of alkaline treatment on flax fibers under extreme weathering conditions.