Abstract
In recent decades, the unique characteristics of natural fibers have promoted their use as reinforcement in polymeric composites. This is verified in several industrial sectors, from packaging to automotive and civil construction. Among the natural fibers, the raffia fiber extracted from the palm tree Raphia vinifera and introduced in the Amazon region a long time ago; started to be considered for the production of polymeric composites only in recent years. For the first time, the effect of raffia fiber length and its alkali treatment on the mechanical properties of a polymer composite was disclosed. Tensile tests were performed in composites with raffia fibers randomly dispersed into terephthalate-based unsaturated polyester resin. The results showed an increase in the Young’s moduli, confirmed by ANOVA, for the composite with both untreated and alkali-treated fibers in comparison to the plain polyester, which characterizes a stiffening effect. The composites with alkali treated fibers exhibited similar tensile strength values for all lengths; however, their strengths are lower than those for the untreated condition due to a weak raffia fiber/polyester matrix adhesion. Therefore, this work fills the current knowledge gap on raffia fiber incorporation in polyester matrix and valorizes this abundant Brazilian resource, providing additional information towards the use of raffia fiber in polymer composites.
Highlights
The alkali treatment is the most commonly used to partially remove the lignin, hemicellulose, wax, and oils covering the external surface of natural fibers, enhancing the matrix–fiber interface and, the composites mechanical properties [10]
In this work, polyester composites with raffia fibers (Raphia vinifera), randomly dispersed, were produced and the effect of both the fiber alkali treatment and fiber length on the mechanical properties were for the first time evaluated
The untreated fibers exhibited average widths and thicknesses of 1.450 ± 0.032 mm and 93.513 ± 4.191 μm, respectively. These fibers showed a dimensional increase of 2% in width (1.487 ± 0.028 mm), and 3.5% in thickness (96.267 ± 3.709 μm), which could be attributed to the volumetric expansion that the fiber suffered during the chemical treatment
Summary
The use of renewable and biodegradable materials has advanced remarkably in recent years. The alkali treatment is the most commonly used to partially remove the lignin, hemicellulose, wax, and oils covering the external surface of natural fibers, enhancing the matrix–fiber interface and, the composites mechanical properties [10] This effect was observed by Mazzanti et al [43] for hemp-PLA composites, in which an increase of ~16% in Young’s modulus was exhibited by the addition of 6 wt% alkali-treated hemp fiber in comparison to the untreated fiber composite. In this work, polyester composites with raffia fibers (Raphia vinifera), randomly dispersed, were produced and the effect of both the fiber alkali treatment and fiber length on the mechanical properties were for the first time evaluated. Based on the only previous tensile results of raffia polymer composites performed so far [32,33], which still cast doubts on a possible reinforcement effect, the present work conducted a statistical analysis by ANOVA and the Tukey test to elucidate this question
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