Walikukun fiber as lightweight polymer reinforcement: physical, chemical, mechanical, thermal, and morphological properties

Natural fibers are increasingly being used as an alternative material to replace synthetic fiber. One of the abundant natural fibers used as an alternative is Walikukun fiber (WF). WF was treated at varied alkali concentrations (KOH). The single fiber strength revealed that the 6% KOH variation produced the highest tensile strength of 454.75 MPa. WF has a high crystallinity index and reached 89.95% with 6% alkali treatment. The result showed that there was a higher cellulose content in the fiber treated with alkali KOH than in the untreated fiber. The FTIR analysis showed that the KOH treatment broke down the lignin part in the characteristic band and increased I-2 cellulose, which made the WF cellulose content higher. The increase in cellulose improved the fiber density, signifying that adding KOH refined the fiber's density. After KOH treatment, the fiber's diameter became smaller and its thickness was reduced. The fiber's crystallinity index indicated improvement in binding lignin and hemicellulose in WF. Thermal testing proved that KOH concentrations positively strengthened the fiber's thermal resistance. The optimal KOH concentration for polymer composites is 6%, which enhances fiber parameters, crystallization index, tensile strength, and thermal stability, making it suitable for reinforcement.