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ABSTRACT:Composites of natural rubber (NR) and short pineapple leaf fiber (PALF) were prepared on a laboratory two-roll mill. The influences of untreated fiber content and orientation on the processing and mechanical properties of the composites were investigated. The dependence of extent of orientation on fiber concentration was also established. Sodium hydroxide (NaOH) solutions (1, 3, 5, and 7% w/v) and benzoyl peroxide (BPO) (1, 3, and 5 wt % of fiber) were used to treat the surfaces of PALFs. FTIR and scanning electron microscope (SEM) observations were made of the treatments in terms of chemical composition and surface structure. The tensile strength and elongation at break of the composites were later studied. The fiber-matrix adhesion was also investigated using SEM technique. It was found that all surface modifications enhanced adhesion and tensile properties. The treatments with 5% NaOH and 1% BPO provided the best improvement of composite strength (28 and 57% respectively) when compared with that of untreated fiber. The PALF-NR composites also exhibited better resistance to aging than its gum vulcanizate, especially when combined with the treated fibers.

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An investigation has been made of the measurement of degree of swelling of vulcanizates and the estimation of υτ, the volume fraction of polymer in a vulcanizate swollen to equilibrium. Methods have been established for dealing with a volatile swelling liquid, allowing for small percentages of nonpolymer in the vulcanizates, testing for diffusion equilibrium and correcting for swelling increment. The resulting values of υτ are suitable for use as described in the preceding Part I.