A two-stage analysis for the role of fiber size in terms of length distribution on the performance under accelerated weathering tests of oil palm empty fruit bunch fiber-reinforced vinyl acrylic composites

The performance of natural fiber-reinforced polymer composites (NFRPCs) can be markedly affected by fiber length, to the extent that a sole mean value and standard deviation fail to accurately represent its overall dispersion. Hence, measuring the variability of fiber length is crucial to comprehend its influence on the properties of the resulting composites. Unfortunately, few studies have been conducted on this topic. This work consisted of two research stages: the first related to the effect of both fiber length distribution and processing temperature on the properties of oil palm empty fruit bunch (OPEFB) fiber-reinforced vinyl acrylic composites, while the second stage analyzed the influence of the fiber length distribution on the material performance under accelerated weathering tests. Broadly, composites were characterized by tensile mechanical testing, optical microscopy and SEM, FTIR spectroscopy, TGA, and microbiological analysis. The key results showed that processing the material at temperatures surpassing 75°C did not lead to a homogenous phase between the components, rendering it unworthy of consideration. Furthermore, composites containing the longest OPEFB fibers exhibited the lowest elongation-at-break values. Regarding the incidence of aging treatments, pronounced effects were observed in those composites exposed to UV radiation and salt fog. In detail, the elongation at break decreased by up to 34%, while the tensile strength increased by up to 1 MPa, and Young's modulus rose by up to 17%. Finally, two fungal genera, Fusarium sp. and Rhizophydium sp., were identified on the OPEFB fibers; nevertheless, no fungal growth was observed on the composites. Highlights: Natural reinforcement/filler size measured as fiber length distribution. Effect of fiber length distribution on composite performance. Composite performance after accelerated weathering tests.