Bio-Polyethylene Composites Based on Sugar Cane and Curauá Fiber: An Experimental Study.

For the purpose of renewable materials applications, Curauá fiber treated with 5% sodium hydroxide was added to high-density biopolyethylene, using an entirely Brazilian raw material of sugarcane ethanol. Polyethylene grafted with maleic anhydride was used as a compatibilizer. With the addition of curauá fiber, the crystallinity was reduced, possibly due to interactions in the crystalline matrix. A positive thermal resistance effect was observed for the maximum degradation temperatures of the biocomposites. When curauá fiber was added (5% by weight), the morphology showed interfacial adhesion, greater energy storage and damping capacity. Although curauá fiber additions did not affect the yield strength of high-density bio polyethylene, its fracture toughness improved. With the addition of curauá fiber (5% by weight), the fracture strain was greatly reduced to about 52%, the impact strength was also reduced, suggesting a reinforcing effect. Concomitantly, the modulus and the maximum bending stress, as well as the Shore D hardness of the curauá fiber biocomposites (at 3 and 5% by weight), were improved. Two important aspects of product viability were achieved. First, there was no change in processability and, second, with the addition of small amounts of curauá fiber, there was a gain in the specific properties of the biopolymer. The resulting synergies can help ensure more sustainable and environmentally friendly manufacturing of automotive products.

Dynamic and Ballistic Performance of Graphene Oxide Functionalized Curaua Fiber-Reinforced Epoxy Nanocomposites.

Graphene oxide (GO) functionalized curaua fiber (CF) has been shown to improve the mechanical properties and ballistic performance of epoxy matrix (EM) nanocomposites with 30 vol% fiber. However, the possibility of further improvement in the property and performance of nanocomposites with a greater percentage of GO functionalized CF is still a challenging endeavor. In the present work, a novel epoxy composite reinforced with 40 vol% CF coated with 0.1 wt% GO (40GOCF/EM), was subjected to Izod and ballistic impact tests as well as corresponding fractographic analysis in comparison with a GO-free composite (40CF/EM). One important achievement of this work was to determine the characteristics of the GO by means of FE-SEM and TEM. A zeta potential of -21.46 mV disclosed a relatively low stability of the applied GO, which was attributed to more multilayered structures rather than mono- or few-layer flakes. FE-SEM images revealed GO deposition, with thickness around 30 nm, onto the CF. Izod impact-absorbed energy of 813 J/m for the 40GOCF/EM was not only higher than that of 620 J/m for the 40CF/EM but also higher than other values reported for fiber composites in the literature. The GO-functionalized nanocomposite was more optimized for ballistic application against a 7.62 mm projectile, with a lower depth of penetration (24.80 mm) as compared with the 30 vol% GO-functionalized CF/epoxy nanocomposite previously reported (27.43 mm). Fractographic analysis identified five main events in the ballistic-tested 40GOCF/EM composed of multilayered armor: CF rupture, epoxy matrix rupture, CF/matrix delamination, CF fibril split, and capture of ceramic fragments by the CF. Microcracks were associated with the morphological aspects of the CF surface. A brief cost-effective analysis confirmed that 40GOCF/EM may be one of the most promising materials for personal multilayered ballistic armor.

Mechanical Properties of Hybrid PVA-Natural Curaua Fiber Composites.

This work presents the experimental study of hybrid cement-based composites with polyvinyl alcohol fiber (PVA) and alkali-treated, short, natural curaua fiber. The objective of this research is to develop composites reinforced with PVA and curaua fiber to present strain-hardening behavior with average crack width control. To achieve this objective, three groups of composites were investigated. The first group had only PVA fiber in volumes of 0.5, 1, and 2%. The composite with 2% PVA fiber was the only one with strain-hardening and crack width control. The second group had 0.5% PVA fiber and volume fractions of 2, 2.5, and 3% curaua fiber, and presented only deflection-hardening behavior. The third group had 1% PVA and volumes of 1, 1.5, and 2% curaua fiber, and presented strain-hardening behavior. Based on the results, the hybrid combination of 1% PVA and 1.5% curaua was the optimal mixture as it presented strain-hardening behavior and crack width control, with a lower volume of synthetic PVA fiber. Additionally, compressive strength and mix workability were calculated for the investigated composites for comparison.

Bio-Based Rigid Polyurethane Foam Composites Reinforced with Bleached Curauá Fiber.

This study aims to evaluate the influence of using a bleached Curauá fiber (CF) as filler in a novel rigid polyurethane foam (RPUF) composite. The influence of 0.1, 0.5 and 1 wt.% of the reinforcements on the processing characteristics, cellular structure, mechanical, dynamic-mechanical, thermal, and flame behaviors were assessed and discussed for RPUF freely expanded. The results showed that the use of 0.5 wt.% of CF resulted in RPUF with smoother cell structure with low differences on the processing times and viscosity for the filled pre-polyol. These morphological features were responsible for the gains in mechanical properties, in both parallel and perpendicular rise directions, and better viscoelastic characteristics. Despite the gains, higher thermal conductivity and lower flammability were reported for the developed RPUF composites, related to the high content of cellulose and hemicellulose on the bleached CF chemical composition. This work shows the possibility of using a Brazilian vegetable fiber, with low exploration for the manufacturing of composite materials with improved properties. The developed RPUF presents high applicability as enhanced cores for the manufacturing of structural sandwich panels, mainly used in civil, aircraft, and marine industries.

Dynamic Mechanical Behavior of Graphene Oxide Functionalized Curaua Fiber-Reinforced Epoxy Composites: A Brief Report.

The coating of natural fiber by graphene oxide (GO) has, over, this past decade, attracted increasing attention as an effective way to improve the adhesion to polymer matrices and enhance the composite properties. In particular, the GO-functionalized 30 vol% curaua fiber (Ananas Erectifolius) reinforcing epoxy composite was found to display superior tensile and thermogravimetric properties as well as higher fiber/matrix interfacial shear strength. In this brief report, dynamic mechanical analysis (DMA) was conducted in up to 50 vol% GO-functionalized curaua fiber reinforced epoxy matrix (EM) composites. The objective was not only to extend the amount incorporated but also for the first time investigate the composite viscoelastic behavior. The GO functionalization of curaua fibers (GOCF) improved the DMA storage (E') and loss (E″) modulus compared to the non-functionalized fiber composites. Values at 30 °C of both E' (13.44 GPa) and E″ (0.67 GPa) for 50 vol% GO-functionalized curaua fiber reinforced epoxy matrix composites (50GOCF/EM) were substantially higher than those of 20 GOCF/EM with E' (7.08 GPa) and E″ (0.22 GPa) as well as non-functionalized 50CF/EM with E' (11.04 GPa) and E″ (0.45 GPa). All these results are above the neat epoxy previously reported values of E' (3.86 GPa) and E″ (0.09 GPa). As for the tangent delta, the parameters associated with damping factor and glass transition temperature were not found to be significantly changed by GO functionalization, but decreased with respect to the neat epoxy due to chain mobility restriction.