Sisal fiber is an important agricultural product used in the manufacture of ropes, rugs and also as a reinforcement of polymeric or cement-based composites. However, during the fiber production process a large amount of residues is generated which currently have a low potential for commercial use. The aim of this study is to characterize the agricultural residues by the production and improvement of sisal fiber, called field bush and refugo and verify the potentiality of their use in the reinforcement of cement-based composites. The residues were treated with wet-dry cycles and evaluated using tensile testing of fibers, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Compatibility with the cement-based matrix was evaluated through the fiber pull-out test and flexural test in composites reinforced with 2 % of sisal residues. The results indicate that the use of treated residue allows the production of composites with good mechanical properties that are superior to the traditional composites reinforced with natural sisal fibers.

Visando a redução da capacidade de absorção de água de fibras ligno-celulósicas, ciclos de molhagem e secagem são usualmente utilizados na indústria de papel e celulose. Esse procedimento enrijece a estrutura polimérica das fibro-células (processo conhecido como hornificação) resultando assim em maior estabilidade dimensional da fibra. No presente estudo foi avaliada a influência da hornificação de fibras de sisal no seu comportamento físico (variações dimensionais e absorção de água), mecânico (comportamento sob cargas de tração direta) e microestrutural (modificações superficiais da fibra e da estrutura das fibro-células). Ensaios de arrancamento da fibra de sisal em matriz de cimento portland foram realizados, utilizando comprimentos de embebimento de 25 mm e 50 mm, com o objetivo de verificar se a possível estabilidade dimensional decorrente da hornificação aumentava a adesão fibra-matriz. Os resultados indicaram maior estabilidade dimensional, redução na capacidade de absorção de água, aumento na resistência à tração e capacidade de deformação e redução no módulo de elasticidade da fibra de sisal com a hornificação. Acréscimos na carga de arrancamento foram observados indicando uma maior aderência da fibra hornificada à matriz de cimento.

The growing global energy demand requires solutions that improve energy efficiency in all sectors. The civil construction sector is responsible for a large part of global energy consumption. In this context, phase change materials (PCMs) can be incorporated into construction materials to improve the energy efficiency of buildings. The purpose of this study was to incorporate a PCM to jute fabric, applying it in civil construction as a reinforcement for cement matrices. In order to do that, a method of immersing jute fabric in liquid phase change material, and then coating it with a polymer, was proposed. Treated jute fabric was then used to produce a laminated composite with a cementitious matrix. Morphological, mechanical and chemical characterization of jute textiles was performed, as well as an analysis of the composites’ mechanical and thermal behavior. The results verified that jute textiles absorbed 102% PCM in weight, which was successfully contained in the capillary porosity of jute. The PCM was able to delay the composite’s temperature increase by up to 24 °C. It was concluded that this method can be used to incorporate PCM to natural textiles, producing composites with thermal energy storage properties.

Hornification is phenomenon that can be promoted by wetting and drying treatment, which modify the microstructure of the lignocellulosic fibers, by promoting the stiffening of the polymeric structure of the fibercells. This process increases fiber mechanical behaviour and reduces water absorption and dimensional variation. The objective of this research is to investigate the influence of several variables on hornification process such as wetting time, fiber/water ratio and the number of wetting and drying cycles on the treatment and its effect on fibers chemical and mechanical properties. Sisal fibers were used. A pre-treatment of 1 h in water (T = 80 °C) and drying at 40°C was applied. Treatments with 1 and 5 cycles of wet and drying were also studied. In both cases two wetting time was applied (1 h and 3 h at 22 °C) and two fiber/water ratio (1:10 and 1:40). The raw and treated fibers were evaluated by thermogravimetric analysis, infrared spectroscopy, wettability analysis, and tensile test. The results showed that lower fiber/water ratios provide better hornification in sisal fibers. Immersion times of 3 hours was efficient to improve tensile strength, increasing stiffness in all studied cases.

The inherent polarity and hydrophilic nature of lignocellulosic fibers and the nonpolar characteristics of polyolefins create challenges in achieving good adhesion between the two materials. This study aimed to evaluate the effect of surface activation of jute fibers on the fiber-matrix interface of a jute fiber-polyester composite. The fibers were pretreated with hot water and exposed to corona discharge for 5 or 10 min. The fibers were evaluated by thermogravimetric analysis, infrared spectroscopy, and scanning electron microscopy. Pullout tests were conducted to evaluate the behavior of jute fibers in the polyester matrix when embedded at 5, 10, 20, and 30 mm depths. The pretreatments did not affect the thermal properties of the fibers; however, they promoted oxidation and increased surface roughness. Hot water pretreatment resulted in partial removal of surface waxes and enhanced bonding. Pullout tests revealed that fibers subjected to hot water immersion, followed by 10 min of corona discharge, exhibited approximately a 34% increase in adhesion strength compared to untreated fibers. It was concluded that corona pretreatment improves fiber-matrix adhesion by activating the surface and increasing the roughness of the fibers.