Curaua Fibers Research Articles

Natural Curaua Fiber-Reinforced Composites in Multilayered Ballistic Armor

The performance of a novel multilayered armor in which the commonly used plies of aramid fabric layer were replaced by an equal thickness layer of distinct curaua fiber-reinforced composites with epoxy or polyester matrices was assessed. The investigated armor, in addition to its polymeric layer (aramid fabric or curaua composite), was also composed of a front Al2O3 ceramic tile and backed by an aluminum alloy sheet. Ballistic impact tests were performed with actual 7.62 caliber ammunitions. Indentation in a clay witness, simulating human body behind the back layer, attested the efficacy of the curaua-reinforced composite as an armor component. The conventional aramid fabric display a similar indentation as the curaua/polyester composite but was less efficient (deeper indentation) than the curaua/epoxy composite. This advantage is shown to be significant, especially in favor of the lighter and cheaper epoxy composite reinforced with 30 vol pct of curaua fiber, as possible substitute for aramid fabric in multilayered ballistic armor for individual protection. Scanning electron microscopy revealed the mechanism associated with the curaua composite ballistic performance.

Biocomposites based on poly(butylene succinate) and curaua: Mechanical and morphological properties

Biocomposites based on poly(butylene succinate) (PBS) and curaua fibers have been produced by compression molding, and investigated as a function of fiber length and amount. Mechanical tests, water uptake and morphology studies were carried out in order to assess the composite features according to the characteristics of the reinforcing agents. It turns out that the impact and flexural strengths increase with fiber content. Moreover, the fiber length, varying from 1 to 4 cm for the composite reinforced with 20 wt% of fiber, influences impact strength, which is higher for shorter than for longer fibers. However, flexural strength is not greatly influenced by the length of the fibers. Water uptake studies reveal a higher sensitivity of the material to fiber content rather than fiber size. Biocomposites, which are characterized by enhanced mechanical properties as compared to PBS, can have different applications, for example in rigid packaging or interior car parts.

Oil‐spill cleanup: The influence of acetylated curaua fibers on the oil‐removal capability of magnetic composites

ABSTRACTA magnetic resin based on cardanol, furfural, and curaua fibers was prepared and characterized. The material could be used in oil‐spill cleanup processes, because of its aromatic/aliphatic balance. The resin was prepared through bulk polycondensation of cardanol and furfural in the presence of curaua fibers and maghemite nanoparticles. Hydrophobicity of the curaua fibers was improved by acetylation, increasing the oil‐absorbing capability of the composites. The obtained magnetic composites were studied by Fourier‐transform infrared spectroscopy, X‐ray diffraction, and thermogravimetric analysis. Degree of cure, magnetic force, and oil‐removal capability tests were also performed. The results show that the composites possess an elevated cure degree in addition to a considerable magnetic force. The materials exhibit a good oil removal capability in the presence of a magnetic field, which is improved by the use of acetylated curaua. In the best case, the composite filled with maghemite and curaua can remove 12 parts of oil from water. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41732.

Curaua Fibers/Epoxy Laminates with Improved Mechanical Properties: Effects of Fiber Treatment Conditions

SummaryThe use of lignocellulosic fibers as reinforcement in polymer composites has increased worldwide recently. Vegetal fibers have low cost and they are commonly available in Brazil. The curaua fibers in particular are of great importance for the development of the Amazon region. The mechanical behavior of the composites reinforced with fibers depends on the effectiveness of the transfer of the applied load by the matrix to the fibers, which is determined by the magnitude of the interfacial bonding between fiber/matrix phases. In this paper, curaua fibers were treated with 0.25–2% (w/v) NaOH solution under tensile loading to improve fiber‐matrix adhesion in curaua fibers/epoxy laminates. Composites with 40 vol.% curaua fibers were obtained. Maximum improvement in the composite properties was observed for those containing curaua fibers treated with 0.5% NaOH under tensile loading. Composites with good bending properties were obtained by using a simple, low cost and environmental friendly method for curaua treatment. This method employed low concentration of chemical solutions, which are neutralized during the process, and no need of heating.

Curaua leaf fiber (Ananas comosusvar.erectifolius) reinforcing poly(lactic acid) biocomposites: Formulation and performance

Formulations of poly(lactic acid) (PLA) reinforced by curaua leaf fibers were prepared and characterized. This biocomposite has material characteristics such as biodegradability and renewability. This work aimed to develop a PLA/curaua leaf fiber composite as a sustainable biodegradable polymer composite. The PLA and composites were thermally, mechanically, and morphologically evaluated. The critical fiber length was studied to check its influence on the mechanical properties. Predictions of the Young's modulus were done to compare with the experimental data, having a reasonable agreement. The Young's modulus increased above 70%, and the impact strength increased 20% compared with the pure PLA. Thermal analysis showed that formulations with up to 20% by weight of fibers were more thermally stable. The fiber modified the crystallinity of the PLA matrix. The best overall balance of properties was attained in composites containing 15% curaua fiber. POLYM. COMPOS., 36:1520–1530, 2015. © 2014 Society of Plastics Engineers

Biodegradable composites: Morphological, chemical, thermal, and mechanical properties of composites of poly(hydroxybutyrate‐co‐hydroxyvalerate) with curaua fibers after exposure to simulated soil

ABSTRACTComposites produced from biodegradable polymeric matrixes reinforced with vegetable fibers have attractive mechanical properties and are environmentally friendly. This work is directed to the biodegradation of a composite made of a poly(hydroxybutyrate‐co‐hydroxyvalerate) matrix reinforced with curaua fibers (with and without alkaline treatment) in simulated soil. The composites were developed by extrusion and injection and were later buried in simulated soil according to the ASTM G160‐03 method. Scanning electron microscopy showed evidence of microbial attack on the samples surfaces. Infrared spectra showed that the composites biodegradation was mainly caused by erosion of the surface layer resulting from microorganisms activity. Thermogravimetric analysis pointed out reduced thermal stability of the samples, and results of differential scanning calorimetry showed that the degree of crystallinity increases and then decreases progressively throughout the degradation period, indicating that enzymatic degradation primarily occurs in the amorphous phase material and thereafter in the crystalline phase. For curaua composite fibers, reductions in tensile strength and elastic modulus are more significant, indicating that the presence of fibers promotes biodegradation of the curaua fiber. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40712.

Selective Reinforcement of High-Impact Polypropylene with Functionalized Fillers

The objective of this work was to prepare composites based on high-impact polypropylene with different functionalized fillers in a mini-extruder, promoting the reaction of the filler surface with the polymer matrix. We evaluated the effect of these fillers on the mechanical and morphological properties of the materials by dynamic mechanical analysis, scanning electron microscopy, and by measuring the amount of hexane extractable after processing. The adhesion between the fillers and hiPP was improved. Moreover, the addition of fillers increased the degradation temperature of hiPP. There was an increase of stiffness and damping factor for samples containing halloysite and curaua fibers.

Analysis of curaua/glass hybrid interlayer laminates

This study compares the mechanical properties of curaua, glass and hybrid curaua/glass laminates evaluated experimentally with those obtained theoretically using commercial software for composites. Hybrids laminates were produced varying the fiber layer stacking sequence with the aim of optimizing the combination of vegetable and synthetic fibers. Composites were compression molded using eight layers of glass and/or curaua fiber mats and mechanically tested as per ASTM standards. The combination of curaua and glass fibers produced a material with intermediate properties and, depending on the type of mechanical loading and the stacking sequence, some hybrids showed properties close to the pure glass fiber composites. Furthermore, hybrid composites with glass layers closer to the surfaces showed the best overall results.

Characterization of Curaua Fibers by Infrared Spectroscopy

Natural fibers obtained from plants are being investigated as possible engineering materials with application in polymer composite reinforcement. For instance, the lignocellulosic fibers extracted from the leaves of the curaua plant (Ananas erectifolius) display a reinforcement potential owing to their relatively high strength. However, the curaua fiber has a poor adhesion with the polymeric matrix. In order to understand the curaua fiber interaction with a polymer matrix, the physical and chemical characteristics need to be evaluated. Among these characteristics, the Fourier transform infrared spectroscopy (FTIR) provides relevant information about the functional molecular groups and their possible interaction. Therefore, the objective of the present work was to analyze the FTIR of curaua fibers by means of transmittance spectrum obtained in the FTIR method with a 60o angle. The results showed peaks corresponding to specific molecular interaction that are discussed and compared to other results.

Efeito do tratamento alcalino de fibras de curauá sobre as propriedades de compósitos de matriz biodegradável

This study investigate the influence of alkaline treatment applied to Curaua fibers, at concentrations of 1, 5 and 10% (w/v) NaOH, on the properties of the composite of PHBV matrix with 20 wt % Curaua fiber. The composites were molded by extrusion and injection and their morphological, thermal and mechanical properties were evaluated. The results showed that alkali treatment caused modifications in the structure of the Curaua fibers by the removal of hemicellulose and lignin, as evidenced by the absence of the typical bands of these compounds in FTIR analysis. It was found an increase of 30% in flexural strength and 12% in impact resistance for the composites with fibers treated in 5% NaOH solution, in relation to composites with fibers without treatment. These results indicate that the alkaline treatment promoted an improvement in the adhesion of the fibers to the matrix, which significantly improved the mechanical properties of the composites. However, concentrations of NaOH solution different from 5% may have a deleterious effect on the mechanical properties of the fibers and composites.

Influência da Espessura nas Propriedades Mecânicas de Compósitos Híbridos Interlaminares de Curauá / Vidro / Poliéster

O interesse do uso de fibras vegetais (ex. juta, sisal e curaua) para aplicacoes mais nobres, como em reforco de materiais compositos polimericos, vem aumentando com o passar dos anos devido a aspectos diversos e, em especial, a legislacao ambiental e a conscientizacao sobre o ciclo de vida dos produtos. Diante deste contexto, o objetivo deste trabalho e obter materiais compositos hibridos interlaminares curaua/vidro/poliester insaturado por moldagem por compressao a quente e analisar a dependencia das suas propriedades mecânicas com a espessura. A resistencia short beam da amostra mais espessa diminuiu devido ao seu maior teor de vazios. Alem disso, a amostra mais delgada apresentou menor dureza, e resistencia ao impacto, a tracao e ao cisalhamento Iosipescu, atribuido em parte a sua menor fracao volumetrica de fibras. De modo geral, o laminado considerado mais adequado foi aquele formado por oito camadas, sendo quatro de fibra de vidro e quatro de curaua, desde que esforcos fletores nao sejam criticos.

Comparison between coconut and curaua fibers chemically treated for compatibility with PP matrixes

Green coconut husk and curaua fibers were submitted to different chemical treatments—acid or alkaline followed by reaction with a silane compound—to improve compatibility between fiber and polypropylene (PP) matrix, in order to obtain composites with better properties than those of pure PP matrix for use as engineering materials. Fiber samples were analyzed before and after treatments to study the effects on thermal stability and morphology. The results showed that the crystallinity index and heat resistance significantly increased when the alkaline treatment followed by silane reaction was applied to both fibers. In this case, the crystallinity index increased from 53% in the coconut fiber in natura to 67% in the treated fiber. Regarding curaua fiber, the increase was from 61% to 81%. The degradation onset temperature of coconut fiber increased from 255℃ to 272℃ and of curaua fiber from 275℃ to 314℃. The treated fibers were mixed with a commercial PP matrix in a twin-screw mini-extruder at 180℃. The composites were analyzed by SEM to observe the compatibility between cellulose fibers and PP matrix.

Mechanical behavior and correlation between dynamic fragility and dynamic mechanical properties of curaua fiber composites

In this study, the mechanical properties and physical–chemical characteristics of curaua composites were evaluated using tensile and short beam testing and dynamic mechanical analysis. Curaua/polyester composites with different pretreatment (washing and drying), fiber length (10–50 mm) and fiber volume fraction (%Vf) (11, 22, and 38 vol%) were studied. The results show that the composites produced using 50 mm long washed/dried fibers and %Vf of 38 vol% achieved better mechanical properties, such as tensile strength and modulus and short beam strength. Fragility index “m” of the composites increased upon curaua incorporation, which may be attributed to a reduction in polyester chemical interactions (due to fiber dwelling of the polyester network). The energy required in initiating the cooperative motion at the “ideal” glass transition temperature and the cooperative rearrangement regions (CRR) also increased upon curaua incorporation, since CRR is considered the subsystem of the sample and for higher fiber content the greater the molecular heterogeneity. Finally, the Angell fragility concept was successfully applied to polymer composite systems. POLYM. COMPOS., 35:1078–1086, 2014. © 2013 Society of Plastics Engineers

Crystallinity, oxidation states and morphology of polyaniline coated curauá fibers in polyamide-6 composites

Abstract Polyaniline (PAni) is one of the most studied conductive polymers due to its ability to exist in various redox states. The possibility of depositing PAni on vegetable fibers and incorporating this in polymeric matrices, such as polyamide-6, enables production of antistatic reinforced materials. In this work, polyaniline was deposited on fiber surfaces on a pilot plant scale and the composites were prepared by extrusion. The microstructures of the polyaniline coated curaua fibers and polyamide-6 were characterized by X-ray diffraction (XRD) measurements and the crystallinity degree of the polyamide-6 was evaluated by differential scanning calorimetry and XRD. Atomic force and electron scanning microscopies were employed to observe the distribution and morphology of the PAni nanoparticles. The oxidation states of PAni were determined by X-ray photoelectron spectroscopy. The results showed that polyaniline supported on the fibers presents amorphous domains and nanometer scale sizes.

Hybridization effect on the mechanical properties of curaua/glass fiber composites

The aim of this paper was to evaluate the effect of hybridizing glass and curaua fibers on the mechanical properties of their composites. These composites were produced by hot compression molding, with distinct overall fiber volume fraction, being either pure curaua fiber, pure glass fiber or hybrid. The mechanical characterization was performed by tensile, flexural, short beam, Iosipescu and also nondestructive testing. From the obtained results, it was observed that the tensile strength and modulus increased with glass fiber incorporation and for higher overall fiber volume fraction (%Vf). The short beam strength increased up to %Vf of 30vol.%, evidencing a maximum in terms of overall fiber/matrix interface and composite quality. Hybridization has been successfully applied to vegetable/synthetic fiber reinforced polyester composites in a way that the various properties responded satisfactorily to the incorporation of a third component.

Antistatic-reinforced biocomposites of polyamide-6 and polyaniline-coated curauá fibers prepared on a pilot plant scale

Curaua fibers were used with success as a reinforcing agent in polyamide-6, however, for several applications, an antistatic dissipation property is also desirable and the incorporation of an intrinsically conducting polymer is a suitable way to promote this. The novelty of this work is the simultaneous introduction of these two properties, antistatic and reinforcement, using one filler, obtained by depositing polyaniline on the surface of short curaua fibers. Nearly 5–30 wt% of these modified fibers were dispersed by extrusion in polyamide-6, the composites were injection molded and characterized by electrical, mechanical, morphological, and rheological properties. The tensile strength of the polyamide-6 composites reinforced with 5 and 30 wt% of polyaniline coated curaua fibers, was 56% higher and 23% lower than the values obtained for pure polyamide-6, respectively. Also, the composite reinforced with 5 wt% of fibers, when processed with lower shearing rates, showed conductivity in the range of antistatic materials, 4 μS cm−1. Scanning electronic microscopy and infrared spectroscopy showed an improvement in interfacial adhesion in PA-6/CF-PAni composites. The composite prepared with 5 wt% of polyaniline coated curaua fibers gave the best balance between the electrical and the mechanical properties. Extrusion and injection molding methods used here are suitable for continuous large scale production. POLYM. COMPOS., 34:1081–1090, 2013. © 2013 Society of Plastics Engineers

The photodegradation and biodegradation of rEPS/curaua fiber composites

The development of composite materials comprised of postconsumer polymers and natural fibers is important for the possibility to obtain materials that are more compatible with the environment. Depending on the application of these materials and their final disposal, the relevant degradation processes must be considered in the studies of these materials. The aim of this work is to evaluate the effect of the degradation process in simulated soil and in the aging accelerated UV chamber on the properties (tensile strength, chemical, morphology) of the composites developed with recycled expanded polystyrene matrix reinforced by curaua fiber. In the tensile strength tests, it was found that the presence of the curaua fiber and the coupling agent did not have significant effect in the degradation processes of the polymer matrix. However, the use of the coupling agent without the addition of fiber curaua promoted the accelerated degradation of the matrix. The carbonyl index was used as the main assessment parameter of the degradation of the composites, since an increasing in the carbonyl index was observed in the initial periods of degradation decreasing for longer time periods. The presence of cracks in the samples following exposure to UV was observed, but no biofilm formation was identified in the samples exposed to the simulated soil. POLYM. COMPOS., 34:967–977, 2013. © 2013 Society of Plastics Engineers

The effect of fiber morphology on the tensile strength of natural fibers

In the present work the morphology of natural fibers was correlated with their mechanical properties via image analysis. Jute, sisal, curaua, coir and piassava fibers were tested under direct tension in a universal testing machine and the cross-sectional areas of the fibers were calculated using images obtained in a scanning electron microscopy. For the jute fiber the tests were performed for several gage lengths in order to investigate its influence on the tensile strength and to compute the machine compliance. For sisal, jute and curaua fibers the amount of fiber-cells, the size of the cell walls and the real area of the fibers were measured and their correlation with the tensile strength addressed. The curaua fiber presented the highest mechanical performance with tensile strength and Young's modulus of 543MPa and 63.7GPa, respectively. Weibull statistical analysis was used to quantify the variability of fiber strength. The sisal fibers presented the highest Weibull modulus (3.70), whereas the curaua presented the lowest one (m=2.2), which means that the sisal had the lowest variability and curaua the highest.

Obtaining nanofibers from curauá and sugarcane bagasse fibers using enzymatic hydrolysis followed by sonication

This paper is an initial study of the implementation of two new enzymes, an endoglucanase and a concoction of hemicellulases and pectinases to obtain cellulosic nanoparticles. In this study, curaua and sugarcane bagasse were dewaxed and bleached prior to enzymatic action for 72 h at 50 °C, and then followed by sonication. The concentration between these two enzymes was varied, and for the concentrations and time of enzymatic treatment used, subsequent sonication was necessary for cellulose nanoparticle release. It was easier to extract cellulose nanofibers from sugarcane bagasse which resulted in nanoparticles without damage of cellulose chains. On the other hand, curaua fibers needed a higher concentration of enzymes and the nanofibers obtained displayed a decrease of crystallinity suggesting that the cellulose structure was compromized. For both fibers, cellulose nanocrystals (single crystals) and larger diameter nanofibers were attained after the sonication.

Preparação e caracterização de biocompósitos baseados em fibra de curauá, biopolietileno de alta densidade (BPEAD) e polibutadieno líquido hidroxilado (PBHL)

Neste trabalho, foram utilizadas fibras de curauá como reforço de matriz termoplástica de biopolietileno de alta densidade. O polietileno foi obtido por polimerização de eteno, gerado do etanol de cana de açúcar. Este polímero é também chamado de biopolietileno (BPEAD), por ser preparado a partir de material oriundo de fonte natural. Desta forma, pretendeu-se contribuir para desenvolver materiais que, dentre outras propriedades, causem menor emissão de CO2 para a atmosfera na sua produção, utilização e substituição, comparativamente a outros materiais. Adicionalmente, polibutadieno líquido hidroxilado (PBHL) foi acrescentado à formulação do compósito, visando a um aumento na resistência à propagação da trinca durante impacto. Os compósitos e as fibras foram caracterizados por várias técnicas, tais como microscopia eletrônica de varredura (MEV), Calorimetria Exploratória Diferencial (DSC), Termogravimetria (TG), além da caracterização dos compósitos quanto à Análise Térmica Dinâmico-Mecânica (DMTA), propriedades mecânicas (impacto e flexão) e absorção de água. A presença das fibras de curauá diminuiu algumas propriedades do BPEAD, como resistência ao impacto. A análise de DMTA mostrou que as fibras geram material mais rígido. Pode-se considerar que a introdução de PBHL na formulação do material foi eficiente, levando a uma resistência ao impacto do compósito BPEAD/PBHL/Fibra maior do que a do compósito BPEAD/Fibra.