Alkaline Treatment Investigation for Sedge Fibers (Cyperus malaccensis): A Promising Enhancement.

Natural fibers have some advantages in comparison to synthetic fibers, especially because they are more environmentally friendly. For this reason, using them as a reinforcement for polymeric matrices is growing exponentially. However, they present the disadvantage of having the hydrophilic nature, which strongly reduces the interface interaction. Sedge fibers have been investigated when reinforcing an epoxy matrix in terms of ballistic properties and mechanical performance. Aiming to enhance the fiber-matrix interface, an alkali treatment was proposed. The group conditions were divided into three NaOH concentrations (3%, 5%, and 10%), as well as the three periods of immersion (24, 48, and 72 h). Therefore, nine different conditions were investigated in terms of their thermal behaviors, chemical structures, physical structures, and morphological aspects. Based on TGA curves, it could be noticed that treatments related to 3% NaOH for 24 h and 48 h exhibited better thermal stability properties. For the time of 48 h, better thermal stability with for a decay of the thermal DSC curve was shown for all treatment conditions. The FTIR spectra has shown a reduction of waxes for higher NaOH concentrations. The XRD diffractogram exhibited an increase in the crystallinity index only for 5% NaOH and an immersion time of 48 h. The morphological aspects of fibers treated with 5% and 10% of NaOH have shown that the treatments have damaged the fiber, which highlighted the crystallinity index reductions.

Evaluation of the Change in Density with the Diameter and Thermal Analysis of the Seven-Islands-Sedge Fiber.

Basic properties of sedge fibers from the seven-islands-sedge plant (Cyperus malaccensis) were investigated with possible application in reinforcing composite materials. A dimensional distribution and the effect of fiber diameter on density were investigated using gas pycnometry. The Weibull method, used to statistically analyze the acquired data from the diameter intervals, indicated an inverse dependence, where the thinnest fibers had the highest density values. The morphology of the fibers was obtained through scanning electron microscopy (SEM), in which a lower presence of defects was revealed in the thinner fibers, corroborating the inverse density dependence. In addition, the sedge fiber was characterized by differential scanning calorimetry and thermogravimetric analysis, which indicate an initial thermal degradation at around 241 °C. These results revealed for the first time that thinner sedge fibers might be promising reinforcement for polymer composites with a limit in temperature application.

Mechanical Properties, Critical Length, and Interfacial Strength of Seven-Islands-Sedge Fibers (Cyperus malaccensis) for Possible Epoxy Matrix Reinforcement.

The growing concern about the limitation of non-renewable resources has brought a focus on the development of environmentally sustainable and biodegradable composite materials. In this context, a trend in the development of natural fibers used as a reinforcement in composites is ever-increasing. In this work, for the first-time, fibers extracted from the seven-islands-sedge plant (Cyperus malaccensis) have been characterized by X-ray diffraction (XRD) to calculate the crystallinity index and the microfibrillar angle (MFA). Also, an evaluation of the ultimate tensile strength by diameter intervals has been investigated and statistically analyzed by both the Weibull method and the analysis of variance (ANOVA). Moreover, the maximum deformation and tensile modulus have been found from the data acquired. Pullout tests have been conducted to investigate the critical length and interfacial strength when sedge fibers, are incorporated into epoxy resin matrix. Microstructure analysis by scanning electron microscopy (SEM) was performed to observe the mechanism responsible for causing rupture of the fiber as well as the effective fiber interfacial adhesion to the epoxy matrix.

Ballistic Properties and Izod Impact Resistance of Novel Epoxy Composites Reinforced with Caranan Fiber (Mauritiella armata).

Natural lignocellulosic fibers (NFLs) possess several economic, technical, environmental and social advantages, making them an ideal alternative to synthetic fibers in composite materials. Caranan fiber is an NFL extract from the leafstalk of the Mauritiella armata palm tree, endemic to South America. The present work investigates the addition of 10, 20 and 30 vol% caranan fiber in epoxy resin, regarding the properties associated with Izod notch tough and ballistic performance. Following ASTM D256 standards, ten impact specimens for each fiber reinforcement condition (vol%) were investigated. For the ballistic test, a composite plate with 30 vol%, which has the best result, was tested with ten shots, using 0.22 ammunition to verify the energy absorption. The results showed that when compared to the average values obtained for the epoxy resin, the effect of incorporating 30 vol% caranan fibers as reinforcement in composites was evident in the Izod impact test, producing an increase of around 640% in absorption energy. Absorbed ballistic energy and velocity limit results provided values similar to those already reported in the literature: around 56 J and 186 J, respectively. All results obtained were ANOVA statistically analyzed based on a confidence level of 95%. Tukey's test revealed, as expected, that the best performance among the studied impact resistance was 30 vol%, reaching the highest values of energy absorption. For ballistic performance, the Weibull analysis showed a high R2 correlation value above 0.9, confirming the reliability of the tested samples. These results illustrate the possibilities of caranan fiber to be used as a reinforcement for epoxy composites and its promising application in ballistic armor.

Copernicia Prunifera Leaf Fiber: A Promising New Reinforcement for Epoxy Composites.

A basic characterization of novel epoxy matrix composites incorporated with up to 40 vol% of processed leaf fibers from the Copernicia prunifera palm tree, known as carnauba fibers, was performed. The tensile properties for the composite reinforced with 40 vol% of carnauba fibers showed an increase (40%) in the tensile strength and (69%) for the elastic modulus. All composites presented superior elongation values in comparison to neat epoxy. Izod impact tests complemented by fibers/matrix interfacial strength evaluation by pullout test and Fourier transformed infrared (FTIR) analysis revealed for the first time a significant reinforcement effect (> 9 times) caused by the carnauba fiber to polymer matrix. Additional thermogravimetric analysis (TG/DTG) showed the onset of thermal degradation for the composites (326 ~ 306 °C), which represents a better thermal stability than the plain carnauba fiber (267 °C) but slightly lower than that of the neat epoxy (342 °C). Differential scanning calorimetry (DSC) disclosed an endothermic peak at 63 °C for the neat epoxy associated with the glass transition temperature (Tg). DSC endothermic peaks for the composites, between 73 to 103 °C, and for the plain carnauba fibers, 107 °C, are attributed to moisture release. Dynamic mechanical analysis confirms Tg of 64 °C for the neat epoxy and slightly higher composite values (82-84 °C) due to the carnauba fiber interference with the epoxy macromolecular chain mobility. Both by its higher impact resistance and thermal behavior, the novel carnauba fibers epoxy composites might be considered a viable substitute for commonly used glass fiber composites.