Immersion In Alkaline Solution Research Articles

Durability assessment of GFRP bars exposed to combined accelerated aging in alkaline solution and a constant load

Employing fiber-reinforced polymer (FRP) bars as reinforcement in reinforced concrete (RC) elements is a promising approach to solve the issues associated with steel corrosion in RC elements owing to the high corrosion resistance of FRP bars. Although a number of studies on the durability of glass FRP (GFRP) bars in the alkaline environment are available, most of which ignored the influence of sustained loads. This paper presents an experimental program on tensile tests on GFRP bars made of three distinct matrix resins (i.e. epoxy, vinyl ester and polyester), after exposure to combined alkaline solution immersion, an elevated temperature and a constant load. A novel level device was developed, and a prescriptive constant axial stress was imposed on GFRP bars, and the bars with or without a sustained load were exposed to an alkaline solution and an elevated temperature of 60 °C. The main parameters investigated in the present study included aging times, constant stress levels, exposure conditions and types of resin matrices of the GFRP bars. The residual tensile properties of the GFRP bars were tested and presented. The microscopy method was adopted to check the internal defects in the GFRP bars with or without exposures. Test results show that three months of exposure in alkali and loading could lead to more than 40% strength decreases of the GFRP bars. Compared with GFRP bars after exposure to alkaline solution solely, the presence of the constant tensile load only leads to small further detrimental effect in tensile properties of GFRP bars.

Study on the Interaction of Plasma-Polymerized Hydrogel Coatings with Aqueous Solutions of Different pH.

Amphiphilic hydrogels from mixtures of 2-hydroxyethyl methacrylate and 2-(diethylamino)ethyl methacrylate p(HEMA-co-DEAEMA) with specific pH sensitivity and hydrophilic/hydrophobic structures were designed and polymerized via plasma polymerization. The behavior of plasma-polymerized (pp) hydrogels containing different ratios of pH-sensitive DEAEMA segments was investigated concerning possible applications in bioanalytics. In this regard, the morphological changes, permeability, and stability of the hydrogels immersed in solutions of different pHs were studied. The physico-chemical properties of the pp hydrogel coatings were analyzed using X-ray photoelectron spectroscopy, surface free energy measurements, and atomic force microscopy. Wettability measurements showed an increased hydrophilicity of the pp hydrogels when stored in acidic buffers and a slightly hydrophobic behavior after immersion in alkaline solutions, indicating a pH-dependent behavior. Furthermore, the pp (p(HEMA-co-DEAEMA) (ppHD) hydrogels were deposited on gold electrodes and studied electrochemically to investigate the pH sensitivity of the hydrogels. The hydrogel coatings with a higher ratio of DEAEMA segments showed excellent pH responsiveness at the studied pHs (pH 4, 7, and 10), demonstrating the importance of the DEAEMA ratio in the functionality of pp hydrogel films. Due to their stability and pH-responsive properties, pp (p(HEMA-co-DEAEMA) hydrogels are conceivable candidates for functional and immobilization layers for biosensors.

Aquivion-based anion exchange membranes: Synthesis optimization via dispersant agents and reaction time

Alkaline membrane water electrolysis fed by renewable energy is a promising technology to produce “green” hydrogen for a variety of applications. Thanks to their unique characteristics of chemical, thermal and electrochemical stability, perfluorinated polymers are proposed as an alternative to hydrocarbon-based anion exchange membranes (AEMs) for applications in water electrolysers. A simple two-step functionalization reaction to introduce quaternary ammonium groups onto Aquivion® perfuorinated backbone is reported using a low toxicity dispersant. The most appropriate dispersant (Novec 7500) and reaction parameters (5 °C for 2 hrs) are selected. The complete conversion of the precursors into a quaternary ammonium salt is confirmed by a solid-state NMR study. Physico-chemical properties, thermal behavior and anion conductivity of the formed AEM are investigated. The phase separation characteristics of this perfluorinated polymer allow to reach a membrane ion mobility (μeff) 1.99 10−4 cm2 V−1 s−1, one order of magnitude higher than the FAA3-50 commercial membrane, meaning an enhanced ion dissociation. A very limited degradation of functional groups is demonstrated after immersion in alkaline solution, with only 2 % of ion exchange capacity (IEC) reduction against 14 % of the FAA3-50 commercial membrane. An electrolysis current density of 0.9 A cm−2 at 2.2 V and 90 °C, is achieved showing very promising applications for green hydrogen production.

Influence of Chemical Operation on the Electrocatalytic Activity of Ba0.5Sr0.5Co0.8Fe0.2O3−δ for the Oxygen Evolution Reaction

Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is a promising electrocatalyst for the oxygen evolution reaction (OER) in alkaline solution. The OER activities of BSCF are gradually enhanced by prolonging the duration of electrochemical operation at OER potentials, but the underlying cause is not fully understood. In this study, we investigated the role of chemical operation, equivalent to immersion in alkaline solution, in the time-course of OER enhancement of BSCF. Interestingly, the time-course OER enhancement of BSCF was promoted not only by electrochemical operation, which corresponds to potential cycling in the OER region, but also by chemical operation. In situ Raman measurements clarified that chemical operation had a lower rate of surface amorphization than electrochemical operation. On the other hand, the leaching behavior of A-site cations was comparable between chemical and electrochemical operations. Since the OER activity of BSCF was stabilized by saturating the electrolyte with Ba2+, “chemical” A-site leaching was key to inducing the time-course OER enhancement on perovskite electrocatalysts. Based on these results, we provide a fundamental understanding of the role of chemical operation in the OER properties of perovskites.

Alkaline solution as a control of Botrytis cinerea, Rhizopus stolonifer, Salmonella spp. and Escherichia coli growth in strawberry (Fragaria x ananassa)

Post-harvest treatments of fruits and vegetables can help to reduce the attack of microorganisms especially the presence of pathogenic microorganisms. Alkaline water solutions were used to control of the growth of Botrytis cinerea, Rhizopus stolonifer, Salmonella spp. and Escherichia coli in strawberry (Fragaria x ananassa). Strawberries were inoculated with the microorganisms and afterwards were immersed in alkaline solutions of pH 11, 12 and 13. In vitro microbiological analyses were used to evaluate the presence of the microorganisms after fruit immersion in alkaline solutions, while the disc diffusion method was used to study the inhibition of microorganism growth. According to the results, alkaline solutions at pH 13 can be utilized to control Botrytis cinerea and Rhizopus stolonifer in strawberries. The immersion of strawberries in alkaline solutions at pH 13 for 60 min allowed to control in vitro development of Salmonella spp. and Escherichia coli.

Effect of Ultrasonic Cleaning of Titanium Turning Scraps Immersed in Alkaline Solution and Subsequent Preparation of Ferrotitanium Ingots

Ti has excellent properties but is more expensive than other materials due to its high melting point, high reactivity and difficult processability. One way to lower the production cost of Ti products is to recycle Ti scraps. Before recycling Ti scraps, pretreatment to remove contamination is essential. Ti scraps can be pretreated in an alkaline solution, thus eliminating the use of acidic solutions. However, a pretreatment only involving immersion in alkaline solution requires a high concentration solution, and has low efficiency. Therefore, in this study, an optimized ultrasonic cleaning process is introduced to pretreat Ti scraps in a lowconcentration alkaline solution. The carbon content of Ti scraps before pretreatment was 6,800 ppm, and showed a sharp decrease with pretreatment. Using this pretreatment process, C, O, and N impurities were removed by 97.6%, 58.8%, and 29.2%, respectively. Ferrotitanium ingots were then produced by vacuum arc melting (VAM) and plasma arc melting (PAM) using the pretreated Ti scraps and electrolytic iron. Differences in ingots melted by VAM and PAM were investigated. As the time was increased, the content of impurities decreased. Subsequently, a ferrotitanium ingot prepared using the pretreated Ti scraps showed that the carbon concentration in the ingot was less than 200 ppm.

Water Absorption, Hydrothermal Expansion, and Thermomechanical Properties of a Vinylester Resin for Fiber-Reinforced Polymer Composites Subjected to Water or Alkaline Solution Immersion.

In the present paper, a vinyl ester (VE) resin, potentially used as a resin matrix for fiber-reinforced polymer (FRP) composite sucker rods in oil drilling, FRP bridge cables, or FRP marine structures, was investigated on its resistance to water and alkaline solution immersion in terms of water uptake, hydrothermal expansion, and mechanical properties. A two-stage diffusion model was applied to simulate the water uptake processes. Alkaline solution immersion led to a slightly higher mass loss (approx. 0.4%) compared to water immersion (approx. 0.23%) due to the hydrolysis and leaching of uncured small molecules (e.g., styrene). Water immersion caused the expansion of VE plates monitored with Fiber Bragg Grating (FBG). With the same water uptake, the expansion increased with immersion temperatures, which is attributed to the increased relaxation extent of the resin molecular networks. Although an obvious decrease of the glass transition temperatures (Tg) of VE due to water immersion (5.4 to 6.1 °C/1% water uptake), Tg can be recovered almost completely after drying. Tensile test results indicate that a short-term immersion (less than 6 months) enhances both the strength and elongation at break, while the extension of the immersion time degrades both the strength and elongation. The modulus of VE shows insensitive to the immersion even at elevated temperatures.

Effect of specimen thicknesses on water absorption and flexural strength of CFRP laminates subjected to water or alkaline solution immersion

Abstract In this paper, an experimental research was undertaken to investigate the effect of specimen thicknesses on water absorptions and flexural strengths of wet lay-up CFRP laminates subjected to distilled water or alkaline solution immersion up to 180 days. Test results showed that the water uptake and flexural strength retention of CFRP laminates were significantly affected by the adopted specimen thickness. For the same aging time, the water uptake of CFRP laminates decreased in the early stage of immersion and increased in the later stage of immersion with the increase of specimen thickness. Meanwhile, the flexural strength retention generally increased as specimen thickness increased. In addition, a new thickness-based accelerated method for hygrothermal aging test of CFRP laminates was proposed. The accelerated factors of the water uptake and flexural strength retention of CFRP laminates were theoretically deduced. The proposed analytical model of accelerated factors was verified with current test data, and then applied to predict long-term properties of CFRP laminates. Compared with the traditional temperature-based accelerated method, the new thickness-based accelerated method is much easier to apply to predict long-term properties of CFRP laminates with good accuracy.

Effects of water or alkali solution immersion on the water uptake and physicomechanical properties of polyurethane

Polyurethane (PU) is an emerging resin matrix for fiber reinforced polymer (FRP) composites. In the present article, effects of immersion in water or alkaline solution on water uptake and thermomechanical properties of a PU were investigated. A traditional epoxy resin matrix was investigated for comparison. As found, unlike the epoxy (hydrolysis occurred in case of alkaline solution), water and alkaline solution immersion showed a similar effect for the PU resin. For both immersion, the water uptake of the PU system reached the equilibrium content of 2.5%–2.7%, in accordance with the Fick's law. Glass transition temperature (Tg) of the PU decreased rapidly after the first month of immersion and then leveled off. Both immersion for a short term (e.g., 1 month of immersion) led to an obvious decrease in the tensile strength, while long‐term immersion brought in obvious recovery. Remarkable increase in the elongation at break (up to 16.6%) due to immersion was found. The higher the immersion temperatures, the less the degradation of the tensile strength. The variations of the thermal–mechanical properties were attributed to the water‐induced plasticization and the postcuring‐induced increase of the crosslinkage. Compared with the common epoxy system, the PU system showed better resistance to the immersion. POLYM. ENG. SCI., 58:2276–2287, 2018. © 2018 Society of Plastics Engineers

Statistical analysis and theoretical predictions of the tensile-strength retention of glass fiber-reinforced polymer bars based on resin type

This paper presents experimental investigation, statistical analysis, and theoretical predictions of tensile-strength retention of glass fiber-reinforced polymer bars, made with vinyl-ester, polyester, or epoxy resins. The durability of glass fiber-reinforced polymer bars was evaluated as a function of time of immersion in alkaline solution. The aging of the three glass fiber-reinforced polymer bar types consisted of immersion glass fiber-reinforced polymer bar samples in an alkaline solution (up to 5000 h) at different elevated exposure temperatures. Subsequently, the physical and tensile properties of the unconditioned bars were compared with that of the conditioned bars to assess the durability performance of the glass fiber-reinforced polymer bars. Microstructure of all of the glass fiber-reinforced polymer bar types was investigated with scanning electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy for both the conditioned and unconditioned cases, to qualitatively explain the experimental results and to assess changes and/or degradation in the glass fiber-reinforced polymer bars. In addition, the long-term performance of glass fiber-reinforced polymer bars was assessed considering the effect of service years, environmental humidity, and seasonal temperature fluctuations. The test results showed that the tensile strength of the glass fiber-reinforced polymer bars was affected by increased immersion time at higher temperatures and the reduction in tensile strength was statistically significantly dependent on the type of resin system. The prediction approach of the glass fiber-reinforced polymer bars based on the environmental reduction factor ( CE) after 200 years indicated that the CEvalues for vinyl-ester, epoxy, and polyester glass fiber-reinforced polymer bars can be conservatively recommended to 0.81, 0.75, and 0.71, respectively, for a moisture-saturated environment (relative humidity = 100%) and at 30℃. The polyester glass fiber-reinforced polymer bars experienced greater debonding at the fiber–resin interface than the vinyl-ester and epoxy glass fiber-reinforced polymer bars.

Effects of water or alkali solution immersion on the water uptake and physicochemical properties of a pultruded carbon fiber reinforced polyurethane plate

Carbon fiber reinforced polyurethane (CFRPU) composites exhibit a high potential in infrastructure application due to their easy manufacturing and excellent mechanical properties. In the present article, a pultruded CFRPU plate subjected to water or alkaline solution immersion at various temperatures was investigated, and compared with a commonly used epoxy‐based CFRP plate, in terms of the water uptake and physicochemical properties. As found, CFRPU plates exhibited excellent resistance to both water and alkaline immersion without noticeable degradation in the mechanical properties. No hydrolysis occurred for CFRPU under both immersion conditions for 1 year at 20–60°C. After 1 year of immersion, the tensile properties of CFRPU kept constant or even were enhanced slightly. On the contrary, the epoxy‐based CFRP plate showed a noticeable hydrolysis, and decreased in the tensile properties remarkably, especially in the case of the alkaline immersion. In addition, unlike the bond between carbon fiber and the epoxy, the bond between the carbon fiber and the polyurethane matrix was not affected by the above immersion. Accordingly, CFRPU was considered to be much more durable in the water or alkaline immersion conditions. POLYM. COMPOS., 40:738–748, 2019. © 2018 Society of Plastics Engineers

Monitoring pH in corrosion engineering by means of thermally produced iridium oxide electrodes

A pH sensor to be used in highly alkaline media under continuous long‐term immersion conditions is crucial in various engineering applications. This work develops the production protocol and posterior conditioning of thermally oxidized iridium (IrOx) electrodes to be used as potentiometric pH sensors embedded in highly alkaline environments such as concrete or cathodically protected steel in soil. The main investigated aspects for the desired applications are the potential‐pH response, its reproducibility, accuracy, and oxygen dependency. The stability during long‐term immersion is also studied in detail. The studied IrOx electrodes responded to pH changes with slopes between −50 and −68 mV/pH unit, even after continuous immersion in alkaline solutions for almost 2 years. Additionally, the electrodes response did not show oxygen dependency. Our results highlight the importance of sufficient conditioning in alkaline media prior to use. When properly produced, conditioned, and pre‐calibrated the electrodes reproducibly permit measuring the pH with a maximum error of 0.5 pH units over a range of at least pH 9–13.5. Preliminary results show that the studied electrodes are promising sensors for monitoring pH changes in concrete.

Long-Life Air Electrode for Rechargeable Zinc-Air Batteries

Energy storage technology is attracting more attention with world-wide increase of renewable energy deployment, such as solar and wind power. With energy storage, electrical energy from photovoltaic cells or wind turbines can be stored when production exceeds consumption and back to the grid when load is demanded. The energy storage devices can also serve as a part of distributed power generation system for remote islands or uninterruptible power supply applications. Usually the system is installed in rural areas and even subjected to harsh temperatures and punishing humidity. Therefore, reliable and efficient energy storage is required. However, most existing mature energy storage technologies, such as Ni-Cd, Ni-MH and Li-ion, can barely satisfy both issues of safety and low cost. Metal air batteries have high theoretical specific energy density, being capable of fulfilling multiple needs for the next generation of mobile/stationary energy storage system. They are also environmentally benign, and inexpensive; frequently used metal anodes including Al, Zn, and Fe are naturally abundant. However, an air electrode with the capability of possessing both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) efficiently is still not well developed at the moment. In the present work, the bifunctional air electrode composed of alpha phase of manganese oxides or silver particles, as ORR catalysts, grown on the surface of stainless steel mesh catalyzing OER, was fabricated via electro-deposition method. This as-synthesized oxygen electrode was used directly for zinc-air battery assembly without polymer binders, which have low conductivity and suffer from detaching when immersion in alkaline solutions, leading to battery failure and short cycle life. In our system, the zinc-air battery was assembled with as-synthesized air cathode, 6M KOH/0.2M zinc acetate electrolytes and zinc foil anode. The battery was operated at the current density of 20 mA/cm2and its charge/discharge potential was 1.95V/1.15V, respectively. In addition, it showed stable performance with >80% coulombic efficiency over 1000 recharge cycles. Acknowledgement: Authors would like to thank the Bureau of Energy (BOE), Ministry of Economy Affair (MOEA), Taiwan for the financial support.

Validation of the alkali contribution by aggregates to the concrete pore solution

Mortar and concrete specimens were made with six reactive and non-reactive aggregates from Eastern Canada, with different alkali contents, to determine their alkali contribution to the pore solution. Two methods were used to determine the alkali content of samples over time: the high pressure extraction method and the espresso extraction method. Also, an alkali leaching test was conducted directly on the same aggregate materials. One aggregate was clearly identified as a potential source of Na+ to the pore solution. Results obtained after one year at 60°C showed that rich alkali-bearing aggregates, which can be identified in an alkali leaching test by immersion in alkaline solutions, can release up to 1.75kg Na2O/m3 of concrete if used as fine fraction and up to 0.24kg Na2O/m3 of concrete if used as coarse fraction. However, no clear K+ contribution from aggregate was observed.

Resistance of basalt fibers to elevated temperatures and water or alkaline solution immersion

In this article, the effects of elevated temperatures treatment (135°C and 300°C for 4 h) and immersion in distilled water or strong alkaline solution (pH 12.6∼13) on the tensile properties of basalt fibers were investigated. As found, the elevated temperature treatment changed the short‐distance order of the fibers, and thus reduced the tensile strength by 2.5% or 32.8% for 135°C or 300°C treated specimens, respectively. At the same time, the discreteness of the fibers was increased which was indicated by the shape parameters of the tensile strength according to the Weibull model. On the contrary, the tensile modulus was not affected by the studied elevated temperatures. Both distilled water and alkaline solution immersions brought in severe degradation in the tensile properties of the untreated and elevated temperature treated basalt fibers. Alkaline solution and high immersion temperatures showed more adverse effects on the degradation of the tensile properties. The basalt fibers immersed in distilled water suffered from etching, and the atom network of the basalt fiber were destroyed due to the hydrolysis of the SiOSi bonds by hydroxyl ion. POLYM. COMPOS., 39:2385–2393, 2018. © 2016 Society of Plastics Engineers

Air Electrode Study for Rechargeable and Long-Life Zinc-Air Batteries

Energy storage technology has become a vital element in the design of electrical networks, especially when renewable energy systems are included. Some other application conditions should be kept in mind that renewable energy system installations are often in remote locations and even subjected to harsh temperatures and punishing humidity. Therefore, reliable and efficient energy storage in both off-grid and on-grid schemes are ultimate developing objects. However, current energy storage technologies, including Ni-Cd, Ni-MH and Li-ion, can barely satisfy both issues of long cycle lifetime and low capital cost. Amongst most developing technologies, the zinc air battery not only provides high theoretical energy capacities, but also includes several advantages, like low cost, environmentally benign and naturally abundant. Some issues remain, hindering commercialization of this technology. One of them is the development of air cathodes possessing both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) efficiently. Hence, much work on bifunctional catalysts development has been done and published by researchers over the world in the past few years. For example, metal oxides/conductive nanocarbon hybrids is proven as an efficient approach to enhancing catalytic activity, such as Co3O4/graphene, CoO/NCNT, and MnxOy/NC. Spinel Mn–Co oxides were also found to be highly active for both ORR and OER. Additionally, long cycle life is a must for us as well. Herein, the bifunctional air electrode composed of alpha phase of manganese oxides or silver particles, as ORR catalysts, grown on the surface of stainless steel mesh catalyzing OER, was fabricated via electro-deposition method. This as-synthesized oxygen electrode was used directly for zinc-air battery assembly without the need of polymer binders mixing for coating on a desired gas diffusion electrode such as carbon papers. Commonly used binders have low conductivity and suffer from detaching when immersion in alkaline solutions, leading to battery failure and short cycle life. In our system, the zinc-air battery was comprised of as-synthesized air cathode, 6M KOH and zinc foil anode. The battery was operated at the current density of 10 mA/cm2 and its charge/discharge potential was 1.97V/1.15V, respectively. Most importantly, it showed stable performance with >80% coulombic efficiency over 2000 recharge cycles (over 600 hours). Acknowledgement: Authors would like to thank the Bureau of Energy (BOE), Ministry of Economy Affair (MOEA), Taiwan for the financial support.

Effect of Colorant Additive and Thickness on Tensile Properties of Oxo-Biodegradable PE Plastic Bags in Alkaline Solution

Polyethylene (PE) is widely used as packaging materials in the form of plastic bags. After end-use, some of these plastic bags are not properly disposed and may persist in different kinds of environment. Oxo-biodegradable plastics are PE films incorporated with pro-oxidants to promote degradation. As part of the continuing study, changes on the tensile properties of oxo-biodegradable PE plastic bags immersed in alkaline solution at 60 °C are investigated. The effects of colorant additive (varied at two levels) and thickness (varied at three levels) on tensile properties of PE films are reported. Specifically, the tensile strength [MPa], strain at break [%], and elastic modulus [MPa] are monitored with time. It is observed that films undergo degradation which is exhibited by a decrease in all tensile properties after 1008 hours of immersion in alkaline solution. Analysis of variance (ANOVA) shows that the initial tensile strength and elastic modulus, as well as the strain at break and elastic modulus after 1008 hours of immersion, are all affected by colorant additive.

Enhancing the biological response of titanium surface through the immobilization of bone morphogenetic protein-2 using the natural cross-linker genipin

Titanium (Ti) is widely used in orthopaedic and dental implants; however, the surface modification methods used to promote osseointegration require further development. In this study, we developed a simple, cost-effective method for the immobilization of bone morphogenetic protein-2 (BMP-2) on Ti surfaces using a natural cross-linker genipin. We then investigated the surface characteristics, including topography, chemistry, hydrophilicity, coating layer adhesion, and protein (albumin) adsorption. In accordance with ISO 10993-5, the cytotoxicity of the resulting materials was evaluated. Human bone marrow mesenchymal stem cell responses, including adhesion, proliferation, and mineralization, were also evaluated. Immersion in alkaline solution resulted in the formation of a porous Ti surface. The use of the cross-linker genipin for the immobilization of BMP-2 on porous Ti surfaces improved the surface hydrophilicity and protein adsorption, which resulted in a non-cytotoxic coating with good adhesion characteristics. The immobilization of BMP-2 on porous Ti surfaces was shown to significantly increase cell mineralization and bioactivity (i.e. Ca/P formation ability), resulting in a biomolecular surface with outstanding potential for bone implant applications.

Pengaruh Fraksi Volume Serat dan Lama Perendaman Alkali terhadap Kekuatan Impak Komposit Serat Aren-Polyester

Palm fiber waste in the industrial processing of starch sugar palm has potential as reinforcing material composite material. This research to determine the effect of fiber volume fraction and long immersion in alkaline solution (NaOH) 5% for the impact strength composites waste palm fiber-polyester. The material used is a waste of palm fiber, unsaturated polyester 157 BQTN, MEKPO catalyst and 5% alkaline solution. Preparation of composites made by the method of press mould. The Composites made with variations of the volume fraction of 10%, 20%, 30%, 40%, 50% and long immersion alkali solution is 0, 2, 4, 6, and 8 hours. The impact test conducted by Izod impact testing machine refers to the standard ASTM D 5941. The results showed that increasing the volume fraction will increase the impact strength, but the subsequent decline. The longer the alkali treatment will reduce the impact strength because the fiber has undergone treatment. The impact strength maximum of the composites with fiber volume fraction of 40% and without alkaline immersion of 0.3211 J/mm2. Characteristics of a broken section of palm fiber composite material are a polyester matrix of a single fracture.

Effects of exposure to elevated temperatures and subsequent immersion in water or alkaline solution on the mechanical properties of pultruded BFRP plates

In this article, a pultruded unidirectional basalt fiber-reinforced polymer (BFRP) plate was thermally aged at 135 °C and 300 °C for 4 h, and subsequently immersed in distilled water or strong alkaline solution (simulating concrete pore water, pH = 12.6–13) for 3 months. The variation of the tensile and interlaminar shear (ILSS) properties of the BFRP plates was studied. Thermal aging exhibited a slight effect on both the longitudinal tensile properties and the interlaminar shear strength, although thermal decomposition of the resin matrix started at 300 °C and brought in a high void content (4.8%). FTIR and DMTA results indicate that thermal aging lead to postcuring and oxidation of the resin matrix, leading to an increase of the glass transition temperatures. Thermal aging accelerated the degradation of the BFRP plates in distilled water or alkaline solution at 20, 40 and 60 °C. In the studied hash immersion conditions of 60 °C alkaline solution for 3 months, the unaged, 135 °C aged and 300 °C aged BFRP samples showed reduction in the tensile strength by 43.2%, 62.3% and 74.1%, respectively. The higher the thermal aging and immersion temperatures, the more deterioration of the mechanical properties occurred. Alkaline solution immersion showed more adverse effects compared to the distilled water. The detrimental effects of the thermal aging were attributed to the formation of voids and cracks through which water or alkaline solution tended to easily penetrate into the BFRPs. The degradation of the resin due to thermal aging and immersion was analyzed with dynamic mechanical thermal analysis and scanning electron microscopy analysis. The long term variation of the tensile strength of BFRPs was evaluated based on the Arrhenius equation.