Untreated Fibers Research Articles

The Effect of Temperature on the Surface Energetic Properties of Carbon Fibers Using Inverse Gas Chromatography

This paper constitutes an original and new methodology for the determination of the surface properties of carbon fibers in two forms, namely, oxidized and untreated, using the inverse gas chromatography technique at infinite dilution based on the effect of temperature on the surface area of various organic molecules adsorbed on the carbon fibers. The studied thermal effect showed a large deviation from the classical methods or models relative to the new determination of the surface properties of carbon fibers, such as the dispersive component of their surface energy, the free surface energy, the free specific energy, and the enthalpy and entropy of the adsorption of molecules on the carbon fibers. It was highlighted that the variations in the London dispersive surface energy of the carbon fibers as a function of the temperature satisfied excellent linear variations by showing large deviations between the values of γsd (T), calculated using different models, which can reach 300% in the case of the spherical model. All models and chromatographic methods showed that the oxidized carbon fibers gave larger specific free enthalpy of adsorption whatever the adsorbed polar molecules. The obtained specific enthalpy and entropy of the adsorption of the polar solvents led to the determination of the Lewis acid–base constants of the carbon fibers. Different molecular models and chromatographic methods were used to quantify the surface thermodynamic properties of the carbon fibers, and the results were compared with those of the thermal model. The obtained results show that the oxidized carbon fibers gave more specific interaction energy and greater acid–base constants than the untreated carbon fibers, thus highlighting the important role of oxidization in the acid–base of fibers. The determination of the specific acid–base surface energy of the two carbon fibers showed greater values for the oxidized carbon fibers than for the untreated carbon fibers. An important basic character was highlighted for the two studied carbon fibers, which was larger than the acidic character. It was observed that the carbon fibers were 1.4 times more acidic and 2.4 times more basic. The amphoteric character of the oxidized fibers was determined, and it was 1.7 times more important than that of the untreated fibers This tendency was confirmed by all molecular models and chromatographic methods. The Lewis acid and base surface energies of the solid surface, γs+ and γs−, as well as the specific acid–base surface energy γsAB of the carbon fibers at different temperatures were determined. One showed that the specific surface energy γsAB of the oxidized fibers was 1.5 times larger than that of the untreated fibers, confirming the above results obtained on the strong acid–base interactions of the oxidized carbon fibers with the various polar molecules.

Effect of alkali treatment on mechanical properties and morphology of the Balanites aegyptiaca composite

The reinforcement of natural fibers in polymer composites is becoming more popular as time goes on due to their biodegradability, availability, lightweight, nontoxic, and nonhazardous characteristics. The goal of this research is to use natural resources like fibers in polymer composites. The matrix was made with the composites of epoxy resin in which fibers derived from the tree of Balanites Balanites aegyptiaca were utilized as reinforcement. To enhance the surface properties of these fibers, they were treated with sodium hydroxide solution (NaOH). By varying weight (5, 10, 15, and 20 wt.%) of the raw fibers treated with NaOH in epoxy resin several composite samples were produced using the hand lay-up technique. The effect of adding Balanites aegyptiaca fibers treated with NaOH to measure mechanical properties such as tensile, bending, and impact, as well as absorption of water and chemical resistance, and SEM morphology was studied. The composite with 15 wt.% Balanites aegyptiaca fibers exhibited the best mechanical properties, absorption of water, and chemical resistance to the composites, indicating that it has the strongest bonding and adhesion between fibers treated with NaOH and epoxy matrix. The surfaces of the tested composites displayed an interfacial adhesion between the matrix and the fibers, which is vividly visible in SEM micrographs of the fractured surfaces of tested composites. The composites that are reinforced with fiber and treated with NaOH are more resistant to water and chemicals than composites with untreated fibers.

Microwave-assisted alkali treatment of sisal fiber for fabricating composite as non-structural building materials

Currently, the world needs sustainable materials to replace and minimize the use of synthetic materials in order to reuce environmental pollution. In this context, natural fiber-reinforced composites (NFRCs) are in high demand. However, the low thermal and mechanical properties have limited their application spectrum. The current research investigation explores the effectiveness of alkali treatment and microwave-assisted alkali treatment (MAAT) on sisal fiber and sisal/high-density polyethylene (HDPE) composites. The MAAT was performed at three different power levels (300, 640 and 800 W) and treatment time was kept constant (10 min); the power level was optimized based on the fiber’s performance. The chemical analysis of treated fibers showed an increased ratio of cellulose percentage in the fibers when compared to untreated fibers. The MAAT (at 640W10) showed improvement in the thermal stability of sisal fiber as compared to untreated and alkali treated fibers. The single fiber test showed the highest (21.92% and 45.77%) increase in tensile strength for MAAT (at 640W10) as compared to alkali treated and untreated sisal fibers, respectively. Scanning electron microscopy (SEM) showed the effectiveness of the MAAT (at 640W10) in terms of a more uniform surface roughness on the fiber surface. The research also focused on using time efficient microwave-assisted molding (MAM) method for the fabrication of NFRCs. Vector network analyzer (VNA) was used to determine the dielectric constant of the fibers as it plays a critical role in heat generation during microwave heating. Mechanical, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) tests were performed on the fabricated composites. It was observed that the MAAT sisal fiber (at 640 W) reinforced HDPE composites (640W10/HDPE) had recorded the best performance as they showed increased thermal stability, percentage crystallinity (3.56% and 10.26%), tensile strength (14.93% and 32.04%) and flexural strength (10.28% and 28.60%) as compared to alkali treated sisal fiber reinforced HDPE composites (NTSF/HDPE) and untreated sisal fiber reinforced HDPE composites (USF/HDPE), respectively. From the results, it is observed that MAAT has strong potential to be commercially employed for the time-efficient treatment of natural fibers before fabricating the sustainable construction components, parts, and products.

A comparative study on the influence of fiber enzymatic treatment in thermal, morphological and mechanical properties of PBS matrix reinforced with different date palm fibers: Under accelerated UV radiation exposure

The use of natural fiber-reinforced polymer materials has become increasingly common in various applications. However, the performance and durability of these composites in outdoor applications are not fully understood. Therefore, the objective of this study is to investigate the impact of an artificial ultraviolet radiation on the degradation behavior of composites based on a Poly Butylene Succinate (PBS) matrix. The reinforcement materials used in this research were the trunk and palm fibers obtained from date palm trees. Specifically, the effect of modifying the fiber surface with an enzymatic treatment on the interfacial adhesion fiber/matrix as well as on the rate of deterioration of the resulted composites, under accelerated aging, was assessed. Changes in the composite’s thermal stability, surface morphology and mechanical properties were determined after aging. A sharp transition in the behavior of the PBS matrix was observed after UV exposure, shifting from slight ductility following 100 h to brittleness after 700 h. The aging process resulted in a decrease in the thermal stability of all composites. However, the composites containing treated fibers exhibited better thermal stability compared to those with untreated fibers. Additionally, the use of enzyme-treated fibers in the composites promoted greater stability in the mechanical properties even after aging. The reinforcement of the composites with palm fibers yielded better interfacial adhesion compared to the use of trunk fibers, and resulted in better retention in the tensile strength property after aging. The enzymatic treatment facilitated stronger physical attachment between the fibers and the matrix, preventing any fiber or interface degradation.

Mechanical and thermo-mechanical behaviors of snake grass fiber-reinforced epoxy composite

Snake grass fiber was used as a supporting material in an epoxy matrix. The goal was to develop a lightweight structural material. To enhance the interfacial bonding between the snake grass (Sansevieria ehrenbergii) fiber and polymer matrices, the fiber underwent chemical treatment with NaOH. Samples were prepared with both neat and treated fibers mixed with epoxy at various volume percentages. The mechanical properties of snake grass fiber exhibited improvement with increasing fiber length and fixation, reaching optimal values at 20 mm length and 20% v/v fixation. Dynamic mechanical analysis (DMA) demonstrated superior energy absorption by the composite up to 140 °C, irrespective of repetition. Thermogravimetric analysis (TGA) indicated rapid degradation of untreated fiber with a residue level of 0.2%, while the snake grass composite (25% v/v) exhibited stable residue content at 11%. Microscopic evaluation using a scanning electron microscope provided insights into the morphology of the fiber surface.

Interfacial properties of carbon fiber‐reinforced biobased resin composites by single fiber fragmentation, fiber push‐out, and interlaminar shear strength

AbstractThe present study examines the interfacial properties of carbon fiber biobased resin composites by comparing the test methods such as the single fiber fragmentation test, fiber push‐out test, and interlaminar shear strength test. The composites were fabricated using a cold vacuum‐assisted resin infusion method for the preparation of fiber push‐out and interlaminar shear test specimens. The interfacial adhesion from the three different test methods is analyzed and compared to determine their relative effectiveness in evaluating interfacial adhesion. Plasma treatment is performed on the carbon fibers and the interfacial shear stress is evaluated by conducting the push‐out test. The surface characterization of the carbon fibers is done by scanning electron microscopy and x‐ray photoelectron spectroscopy to investigate the influence of the plasma treatment on the fiber surface. Plasma treatment resulted in significant improvement in the interfacial adhesion between the fiber and matrix.Highlights Analysis and comparison of interfacial adhesion by several test methods. Single fiber fragmentation and push‐out tests with IFSS of 40.5 and 42.2 MPa. Plasma surface treatment improved the IFSS by 88.1%. Surface characterization of treated and untreated fibers by SEM and XPS.

Flax fiber treatment by an alkali solution and poly(dopamine) coating: Effects on the fiber physico-chemistry and flax/Elium® composite interfacial properties

The use of natural fibers to reinforce polymer-based composites is gaining interest to replace conventional synthetic fibers due to their sustainability. In this frame, optimizing the adhesion between natural fibers and the polymer matrix is crucial to ensure high mechanical properties. To improve the adhesion between flax fiber and an acrylic-based thermoplastic resin, the combining of alkalization and poly(dopamine) (PDA) coating as fiber treatments has been investigated in this paper. It is found that applying an alkalization with sodium hydroxide (3 wt%, 2 h, 21 ± 2 °C), followed by dopamine polymerization (2 g/L, pH of 8.5, 24 h, 21 ± 2 °C) in the presence poly(ethylene imine) (600 g/mol, 1 g/L) as a polyelectrolyte, provides the highest increase in composite interfacial shear strength (+22.0 %) and interlaminar shear strength (+63.2 %) compared to the composite with untreated fibers. The results are discussed based on the fiber physico-chemical properties and composite interfacial aspects.

STUDYING THE PROPERTIES OF FINE-GRAINED CEMENT CONCRETE USING PLASTICIZERS AND BASALT FIBER

The article deals with the experimental and theoretical substantiation of the use of basalt fiber as a promising material that can be used to produce a new class of building materials. The nature of the dependence of cement concrete properties on the method of introducing heattreated fiber and the type of plasticizer is revealed. The most effective is the preliminary loosening of the fiber in the mixing water in the presence of a naphthalene-formaldehyde superplasticizer, followed by the introduction of the suspension into the molding mixture. Adsorption of the plasticizer on the surface of the fiber leads to hydrophilization of its surface, which contributes to the uniform distribution of the fiber throughout the mixture and, as a result, increases the strength of the concrete. The use of the naphthalene-formaldehyde additive SP-1 makes it possible to increase the compressive strength by 10% and the flexural strength by 21% compared to formulations based on the polycarboxylate plasticizer Sika Visco Crete. The compositions of fine-grained concrete using heat-treated basalt fiber have been developed, which make it possible to obtain materials with class B25...B60 in terms of compressive strength; Btb2.8...Btb6.0 in terms of bending strength; frost resistance not less than F300. The analysis of the microstructural features of fiber concrete with reinforcing basalt microfiber shows that the modified (heat-treated at 500 °C) fiber in the cement matrix performs its function due to changes in its surface properties. The fiber acts as a substrate for the active crystallization of clinker minerals, which helps to increase the adhesion of binder hydration products to the fiber. This is due to the increased alkali resistance compared to untreated fiber, and, consequently, its stability and strength in the aggressive environment of cement batter, as well as due to its relatively higher activity. These circumstances are obviously the main reasons for the increase in the flexural strength of composite materials (concretes) using the studied cement systems.

Development of a novel sandwich-structured composite from biopolymers and cellulose microfibers for building envelope applications

A novel sandwich-structured composite was developed from the surface layers of polyhydroxyalkanoate (PHA) and the interlayer of polylactic acid (PLA)/cellulose microfibers (CMF) composite. Moreover, CMF was chemically modified via a sol–gel process to improve the compatibility between the natural reinforcement and the polymer matrix. According to the obtained results, the modified CMF exhibited a highly hydrophobic characteristic (contact angel value of approximately 118°), and they were homogeneously dispersed in the PLA matrix. The results of the thermogravimetric analysis indicated that the sandwich composites reinforced with the modified CMF showed improvement in thermal stability. Regarding the mechanical properties, the incorporation of the natural reinforcement into sandwich composites increased the values of tensile modulus and strength of materials. The water vapor permeability of sandwich composites increased with the addition of untreated fibers; however, the composites reinforced with the modified CMF showed superior barrier performance than that of untreated CMF. In addition, a durability test was performed to determine the effect of accelerated aging on the properties of sandwich composites. The results demonstrated that the mechanical and barrier properties of composites incorporated with untreated CMF decreased after the accelerated aging, whereas the composites reinforced with the modified CMF experienced the least change.

Preparation of CNTs/SCF reinforcement using multiple continuous surface treatments to achieve synergistic improvement of epoxy resin-based composites interfacial properties: Towards industrial production of carbon fiber surface treatment

The silane/maleimide co-modified waterborne polyurethane (WPU-M-S) sizing agent and furan-functionalized carbon nanotubes (CNTs-FA) were prepared through chemical modification method. The continuous grafting of carbon nanotubes (CNTs) was realized on the carbon fiber surface by multiple continuous surface treatments, including electrochemical anodizing (EAO), sizing, and chemical grafting of CNTs. The stable physical and chemical connection between carbon fiber, sizing agent, and resin was constructed through the preparation of CNTs/SCF reinforcement. The results of different surface treatment processes such as ultrasound and CNTs grafting process were contrastively studied in terms of surface morphology, microstructure, and mechanical properties. It is reflected that carbon fiber grafted with CNTs-FA (CNTs/SCF) that were prepared by ultrasound assisted chemical grafting provide optimal wettability and interfacial performance. The interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of CNTs/SCF reinforced epoxy resin composites are 115.37 % and 93.91 % higher than those of the untreated carbon fiber (UCF), respectively. The synergistic improvement mechanism of reinforcement on carbon fiber reinforced epoxy resin composites interfacial properties was proposed. This research provides a multiple continuous surface treatment technology that matches the industrial production of carbon fiber to prepare CNTs/SCF reinforcement.

Simultaneous saccharification and fermentation residues as potential sources of phenolics by fast pyrolysis (Py-GC/MS) and alkaline hydrolysis

Unlike 1 G bioethanol, the success of 2 G technology faces difficulties. The economic difficulties of 2 G bioethanol can be solved with an additional income in by-products, mainly from lignin. The present study investigated the generation of phenolics via fast pyrolysis and alkaline hydrolysis using residues from saccharification and simultaneous fermentation (SSF) as substrate. The SSF residues were obtained from schemes with green coconut fiber (without chemical pretreatment) and corn cob (with previous acid pretreatment). Chemical composition, FTIR, and XRD analyses confirmed that the processing undergone by SSF residues altered the lignocellulose structure. Due to extractives removal and lignin increase, the fast pyrolysis experiments with SSF residues favored the generation of phenolics over C1-C4 products. Phenol was the main product in the pyrolysis of untreated green coconut fiber (14.64%) and SSF residue (13.51%), while the 2-methoxy-4-vinylphenol content in the bio-oil was doubled with the SSF corn cob residue (from 12.87% to 27.01%). SSF corn cob residue showed a high yield of hydroxynamic acids after alkaline hydrolysis with sodium hydroxide. The p-coumaric acid yield reached 4337 mg/100 g in experiments at 60 °C. Based on the results, the conversion of SSF residues appears as an alternative to obtain commercially appealing phenolics and may be attractive for 2 G bioethanol technology.

Enhancement of water absorption properties of date palm fibers-based composites via alkaline treatment

This study examined the ability of a biodegradable composite material to absorb water. The composites were created by combining a matrix of polylactic acid (PLA) with date palm wood fibers (DPWF) for reinforcement. Before incorporating the fibers into the polymer, they underwent chemical treatment using alkali solutions of NaOH and KOH. This treatment aimed to modify the surface properties of the natural fibers and enhance their water absorption capabilities. Different composites were fabricated, including PLA combined with untreated fibers (PLAUF), and PLA with treated fibers using both NaOH and KOH (PLAF-NaOH and PLAF-KOH), with varying weight percentages of fibers ranging from 0 to 40%. To evaluate the water absorption capability of the composites, water retention tests were conducted at room temperature (cold) and 50 °C (hot) for 24, 48 h and until the absorption reached equilibrium. The results demonstrated a significant enhancement in water retention, particularly in the case of the NaOH-treated samples, which exhibited approximately a tenfold increase in water retention compared to untreated samples. For example, the 20 wt% NaOH treated filler had a hot-water retention of 20%, compared to 2% for the untreated filler. Additionally, a higher percentage of filler resulted in a higher rate of water absorption. The 40 wt% NaOH treated sample with 20% water retention, absorbed 10 times more than the 10 wt% NaOH treated filler, with only 2% water retention. The developed composites have potential applications in natural gas dehydration processes, offering an alternative to the energy-intensive and environmentally harmful glycol-based dehydration methods currently in use.

Biosoftening of banana pseudostem fiber using cellulase and pectinase enzyme isolated from Aspergillus niger for textile industry

BackgroundNowadays, farmers are facing a lot of problems for the disposal of banana pseudostem waste after the harvesting of banana. Banana pseudostem is a rich source of fiber, which is an alternative source of other natural and synthetic fibers. The banana fibers are biodegradable, and they are expected to be in great demand in the international market. For the textile industry, fibers were extracted using chemical and mechanical methods, but it leads to damage and affects the quality of fibers. So, this study mainly focused on biosoftening of banana pseudostem fiber using crude enzyme produced from Aspergillus niger which is one of the most predominant fungus which can synthesize industrially applicable enzymes and which can soften the surface of banana pseudostem fiber. Through this, biosoftened banana pseudostem fiber can be produced, and the disposal problem of banana pseudostem can be rectified in an eco-friendly manner. ResultThe present study was undertaken for the biosoftening of banana pseudostem fiber using crude enzymes isolated from fungal strain. The fungal isolates were subjected to enzyme screening such as cellulase, pectinase, chitinase, peroxidase, and polygalacturonase. The maximum production of enzyme was observed in F2 strain, and it was subjected to crude enzyme production and purification using dialysis and column chromatography. The collected best enzyme fractions were selected for the biosoftening of banana pseudostem fiber. The banana pseudostem fiber was treated with crude enzymes at the time duration of 2, 4, 24, and 48 h. After the treatment, the treated and untreated fibers were evaluated for the mechanical properties and chemical constituent’s analysis. The results revealed that the chemical contents were high during 2- and 4-h-treated fibers. After that, chemical constituents were reduced due to the removal of debris by the action of enzymes. The mechanical properties such as breaking load, breaking extension, tenacity, and diameter of fiber were best in the fibers treated for 2 and 4 h. After 4 h due to the removal of chemical constituents the breaking load and tenacity, diameter will be reduced. SEM results proved that the fiber treated at 4th h showed smooth and softened fiber. ConclusionThis study proved that the crude enzymes isolated from the Aspergillus niger can be effectively soften and increase the quality of banana pseudostem fiber.

Performance assessment of surface modified natural fibre using NaOH in composite concrete

Abaca fiber degradation in concrete owing to its alkaline nature decreases the strength of concrete. This research focuses on overcoming the degradation by alkaline treatment with sodium hydroxide (NaOH) to improve fiber performance. This study was completed with the extraction process of fiber, mechanical properties, micro-structural analysis of composite fiber concrete for both M30 and M40 grades, and durability performance if the fiber content, aspect ratio of fiber and molarities of Sodium Hydroxide were optimized using splitting tensile strength of the concrete matrix and it was found that the optimum percentage of fiber content was 1% at 12% alkali treatment. The composite concrete has achieved an increase of 2700 to 3100 kg m−2 in split tensile strength with treated abaca fibers compared to untreated fiber concrete. In addition, treated abaca fiber concrete provides better performance in mechanical and durability studies. The binding nature of fiber concrete is better than that of conventional concrete, which is evidenced in microstructural analysis. This study ultimately concluded that the treated abaca fiber composite concrete is a better alternative to commercially available untreated abaca fibers and other natural fibers.

Effects of alkaline treatment and manufacturing process on mechanical and absorption properties of Wild Abyssinia Banana fiber reinforced epoxy composite

To enhance the properties of natural fiber composite, proper selection of an optimum alkaline concentration for fiber surface modifications and composite manufacturing techniques are the main criteria to be considered. This study examined how NaOH and manufacturing methodsaffect the mechanical and absorbency characteristics of a Wild Abyssinia Banana (WAB) epoxy composite. 2 %, 5 %, and 7 % (w/v) NaOH concentrations; hand-layup and hydraulic press manufacturing techniques have been considered. Petroleum, diesel, distilled, and artificial lake water (wastewater) were used for the absorption test. A 5 % NaOH treatment improves composite tensile, flexural, and impact strengths by 14.78 %, 8.59 %, and 29.63 %, respectively. Moreover, the 5 % NaOH treatment reduced the absorption rate of the WAB fiber composite. Hydraulic press manufactured untreated WAB fiber composite was observed to have 26.27 % and 13.45 % higher tensile and flexural strengths than hand layup. The treated WAB fiber-reinforced composite can be utilized in gas stations, home appliances, and finishing materials for construction applications.

Matrix-Material Fabrication Technique and Thermogravimetric Analysis of Banana Fiber Reinforced Polypropylene Composites

From the environmental consideration, it would be very interesting to use natural fibers such as banana, jute or coir as reinforcement materials instead of artificial fibers or any kind of synthetic materials. Natural fibers have many advantages over synthetic ones. Polypropylene banana fiber composites (PPBC) are prepared using untreated and alkalitreated banana fibers at 10-25% by weight of the fiber loading. The thermal properties of polypropylene natural fiber composites are very important for technological uses. Thermogravimetric measurements show that the incorporation of banana fiber into PP enhances the thermal stability of composites containing treated fibers, in comparison with untreated fibers. A composite of biodegradable polypropylene (PP) reinforced with short banana natural fibers was prepared by melt blending followed by a hot press molding system. The thermal properties of matrix materials were studied using thermogravimetric analyzers TGA units. It is observed that the introduction of short banana fibers slightly improved the thermo oxidative stability of PP-banana composites. Physical and chemical changes occurred through dehydration, phase transition, molecular orientation, crystallinity disruption, oxidation and decomposition, and incorporation of several functional groups. Systematic investigations of the thermal behavior of polymers in gas, vacuum or inert atmosphere give the knowledge of how change takes place in polymers. To understand such changes thermogravimetric analysis (TGA) and thermal analysis (TG) were performed. It is observed reinforcement of short banana fiber leads to little improvement in the thermooxidative stability of PPBC. Due to the enhancement of thermo-mechanical properties, such composites may be used as building materials namely roof materials, selling materials and many other engineering applications.

An experimental investigation of flame retardancy and thermal stability of treated and untreated kenaf fiber reinforced epoxy composites

Abstract Natural fiber reinforced polymeric composites perform poor in mechanical and thermal properties at elevated temperatures due to the cellulose and hemicellulose contents of natural fiber start degrading at elevated temperature. In this research work, flame retardancy and thermal stability of treated and untreated kenaf fiber reinforced epoxy composites have been experimentally investigated and reported. Two composite laminates, one with 6 % NaOH Alkali treated and another with untreated woven kenaf mats, were fabricated by hand lay-up technique followed by compression molding with 40 % fiber weight fractions. Flame retardancy test and various thermal characteristics studies such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), heat deflection temperature (HDT), and morphological analysis via scanning electron microscopy (SEM) tests were carried out. The results showed that alkali treated kenaf fiber composite achieved V0 fire retardancy grade. The major weight losses, 86 % and 75.5 % for untreated and treated composites respectively were recorded between 300 °C and 450 °C. 13.6 % increase in HDT was noted for treated composite with 0.25 mm deflection at 0.45 MPa pressure condition. Thus the composite laminate with 6 % NaOH alkali-treated kenaf fiber achieved the best thermal stability with less degradation which is more suitable for automobile and aerospace applications.

Assessment of graphene oxide coated polyester fiber reinforced cementitious composites

The study of fiber-reinforced concrete (FRC) is associated with improving the mechanical properties of the material, but it will only be sufficiently efficient when there is an interaction between the fiber and the matrix, which depends on the characteristics of the paste, and mainly on the characteristics of the surface of the reinforcement material. In this way, this research sought to evaluate the surface treatment of polyester fibers (F) with graphene oxide (GO) and its contribution to the transition zone (fiber-matrix) in concrete mixtures. The surface deposition on the fiber was carried out using the ultrasonication method with temperature variation reaching two maximum temperatures (50 °C and 80 °C), then reinforced concrete mixtures were obtained using the untreated fiber (FRC), fiber with GO auxiliary coating (FRC/GO) and GO (GOC). To evaluate the quality of GO deposition, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) tests were carried out, the same technique was used to evaluate the fiber-matrix transition zone, and tests were also carried out in the fresh and hardened for concrete mixes. The SEM images and the C/O ratio identified in the EDS demonstrate greater deposition of GO in fibers treated at 80 °C, increasing the C/O ratio by 47 % when compared to samples without treatment and 44 % higher than the treatment at 50 °C. It is possible to identify in the SEM images the change in the fiber-matrix transition zone for the FRC/GO samples, and in them the formation of denser regions of cement hydration products, which did not represent gains in mechanical properties, but rather 19 % reduction in water absorption when compared to FRC samples.

Development of “Cissus quadrangularis” Composite Material with Elevated Mechanical Properties and Thermal Stability

The main objective of this work is to evaluate the mechanical and thermal strength of a recently developed composite made of Cissus quadrangularis fiber coupled with Polylacticacid (PLA) in comparison to other natural fibers. This study investigated three different fiber and PLA compositions—20%, 30%, and 40%, respectively used to produce a composite. In contrast, another composite with the same volume percentage was created using calcium hydroxide Ca(OH)2 to coat the fibers in order to alter their microcrystalline structure and enhance their mechanical properties. The composite was created using an injection molding procedure. Tests were performed to assess the improved properties. According to a preliminary study, the mechanical characteristics of PLA combined with treated Cissus quadrangularis fiber are increased when compared to PLA coupled with untreated Cissus quadrangularis fiber and neat PLA. Calcium hydroxide acted as a binding agent in fiber to enhance stress transmission in the matrix, increasing tensile and flexural modulus as well as toughness elongation. Further DSC analysis showed that the inclusion of the preceding components increased the glass transition temperature and melting temperature. The temperature at the beginning of deflection has risen as a result of showing how increasing HDT, fiber–matrix adhesion, and fiber content are related. The morphological analysis was performed on both untreated and chemical-treated fiber composites by using an optical microscope to see the interaction with the fiber matrix.

Extraction and Characterization of Natural CASCABELA Thevetia Bast Fibers: A Potential Candidate as Reinforcement in Epoxy Composites

ABSTRACT The aim of this study is to explore the potential of CASCABELA thevetia (CT) bast fibers as reinforcement in polymer composites. For this purpose, the extracted fibers were chemically treated with various chemicals such as sodium hydroxide, potassium permanganate, sodium chlorite, and benzoyl chloride. After surface modifications, its physical and mechanical properties, chemical composition, and structure were studied. The X-ray diffraction (XRD) results revealed an increase in crystallinity index of the fibers as compared to untreated fibers with benzoyl chloride treated fibers showing the optimum result which agrees with the results obtained in the mechanical tests. Composites were fabricated by taking various wt.% of benzoyl chloride treated CT fibers in an epoxy matrix (i.e. 5, 10, 15, 20, 25, and 30 wt%) and their mechanical and wettability tests were carried out. It was observed that composites with 20 wt% of fiber loading show the highest mechanical properties (52.79 MPa tensile strength, 2.45 GPa Young’s modulus, 71.72 MPa flexural strength). All the fabricated composites showed contact angle less than 90°, which is associated with composite hydrophilic surface properties. These composites can be utilized in lightweight structural material and in automobile industries owing to its better properties.