Surface modification of abaca fibers by permanganate and alkaline treatment via factorial design

Natural fibers are utilized as alternative for synthetic fibers in various fiber-reinforced composites, and abaca fibers are the most commonly used for their strength and abundance. However, natural fibers can form a weak interfacial bonding with the polymer matrix due to their hydrophilic properties. In this study, the permanganate (KMNO₄) and alkaline (NaOH) chemical treatment were used to modify abaca fibers. The effects of varying concentrations and soaking time to the fiber-matrix bonding were investigated. Fibers treated with permanganate only produced the highest tensile strength, with an increase of as much as 26.37%. Moreover, the same treatment resulted to the lowest moisture regain due to the gum removal, and effectively getting rid of polar groups in the treated fibers. Surface texture of the treated fibers had a rougher surface, which can possibly contribute to better mechanical interlocking of the fiber and matrix. However, excess gum removal at high concentrations resulted to fiber damage and lower mechanical strength as observed in the treatment combination of sodium hydroxide and permanganate at the longest soaking time.