Water Uptake Tests Research Articles

Production of Biodegradable Straw from Banana Peel

This study aims to determine the effect of enhancement in stirring temperature (75oC, 80oC, 85oC) and type of plasticizer (glycerol and sorbitol) on the characteristics of biodegradable straw from ambon banana peel waste and to compare them with the characteristics of conventional boba’s straws. Methods used in this study were tensile strength, elongation, biodegradation, and water uptake tests. The result showed enhancement of stirring temperature and type of plasticizer did not significantly affect the characteristics of biodegradable straws from ambon banana peel waste (p > 0.05). Enhancement of stirring temperature will increase the tensile strength and water resistance value, but decreased elongation and biodegradation value because enhancement of stirring temperature will decrease the water content and increase the molecular density. In addition, plasticizer will increase elongation value and level of biodegradation, but decrease tensile strength and water resistance values. Plasticizer has the ability to increase the elasticity of polymers, as well as increase water absorption because it has hydrophilic hydroxyl groups. Biodegradable straw that have been developed has a colour of black, being rigid, with a length of 13 cm and an external diameter of 1.2 cm. The colour and external diameter of biodegradable boba’s straw looks similar with conventional boba’s straw but shorter in length. Therefore, ambon banana peel waste was promising to be used as an alternative material for biodegradable straw in the future.

Antibacterial efficiency over time and barrier properties of wood coatings with colloidal silver

This work aims to represent a standard application for understanding the extent of the antibacterial efficacy of coatings with different amounts of colloidal silver on wooden surfaces over time. The key variable that was intended to be evaluated in this study was the “time efficiency,” with concerns about the possible efficacy in the durability of the surfaces. By highlighting the “expiry date” of the agents, as in the case with other products, the study aimed to confirm the validity of the simulation tests conducted in the laboratory with degradation tests. Furthermore, the role of the silver amount on the barrier performance of the coatings was assessed by liquid resistance, water uptake, and perspiration tests, evaluating the aesthetic durability of the coatings by means of colorimetric analyses. Ultimately, this work demonstrates that these coatings may represent alternatives in terms of prolonged antimicrobial activity when compared with the biocide agents currently in use, capable to offer good resistance to detergent solutions and to water. Nevertheless, due to silver’s susceptibility to extended exposure to acidic solutions, the findings of the research discourage the utilization of colloidal silver in wood paints intended for use in public settings.Key points• Colloidal silver does not alter the deposition process and does not introduce defects in the wood paint.• Coatings containing silver show high antimicrobial activity over time, against both E.coli and S.aureus.• The silver-based filler resists contact with detergents and aqueous solutions but suffers oxidation processes in acidic environments.

Interlaminar Shear Property and Strength Prediction Model for Hybrid Fiber-Reinforced Polymer Bar after Exposure to Simulated Concrete Environments

The load-transfer mechanism in the fiber-reinforced polymer (FRP) bars is different from that of the conventional steel bars. The efficiency of stress transfer in FRP bars mainly depends on the mechanical properties of matrix resin, fibers, and fiber/matrix interface, which are easily degraded after long-term exposure to concrete environment. Herein, the interlaminar shear properties of a novel carbon/glass hybrid fiber-reinforced polymer (C/G-HFRP) bar were experimentally investigated by the accelerated aging tests at 60°C to study the effects of the ratio of carbon to glass fiber volume fractions, distribution configuration of carbon fiber, total fiber volume fraction, exposure environment, and exposure period. Water uptake tests, scanning electron microscopy, and Fourier transform infrared spectroscopy were employed to explore the degradation mechanisms of exposed samples. The results indicated that the interlaminar shear strength (ILSS) retention of exposed C/G-HFRP bars was higher than that of the single glass-FRP bar, which was decided by tooth force and friction. In addition, the degradation of C/G-HFRP bars was also related to water uptake rate, and then waterproof coating and fiber modification are recommended to improve the durability of C/G-HFRP bars. Finally, a model of ILSS retention was proposed for the C/G-HFRP bars after exposure to different concrete environments.

A long-term anti-corrosion and cathodic delamination resistant epoxy coating based on COF grafted GO nanofillers

Here, a long-term anti-corrosive epoxy (EP) coating based on nano-hybrid filler was developed. The surface of graphene oxide (GO) was aminated with (3-aminopropyl) triethoxysilane (APTES), and then the porous covalent organic framework (COF) was in-situ grown on amino functionalized graphene oxide (FGO) nanosheets by Schiff-based reaction to prepare FGO-COF nanofillers. Different characterization methods proved the successful modification of GO nanosheets with COF particles. The excellent water resistance of composite coatings was characterized through contact angle, adhesion, and water uptake tests. Transmission electron microscope (TEM) and molecular dynamics (MD) methods showed that the grafting of COF enhanced the dispersion and compatibility of GO in the coating. EIS measurements, salt spray analysis and cathodic delamination test indicated the significant improvements in the protective properties of the composite coatings compared with pure EP coating. The low-frequency impedance modulus of 1% FGO-COF composite coating reached higher than 6.8 × 109 Ω·cm2 after immersed in sea water for 60 days. In addition, the 1% FGO-COF composite coating performed only 34% delamination ratio after 120 h cathodic delamination test.

Improvement of mechanical properties of jute-nano cellulose-reinforced unsaturated polyester resin-based composite: Effects of gamma radiation

In this research work, waste jute bags were utilized to synthesize nano cellulose which was further applied as reinforcing materials for the fabrication of unsaturated resin-based composites. Different percentages of nano cellulose were used to fabricate nano cellulose-reinforced unsaturated polyester resin-based composites and the composites were fabricated using the hand-lay-up technique. A 0.2% (w/w) incorporation of nano-cellulose in the matrix enhanced the mechanical properties of the fabricated composites. A variation was also maintained for high-energy gamma radiation doses such as 2.5, 5.0, and 7.5 KGy which were applied throughout the fabricated composite to enhance the properties. Higher mechanical properties were found for the incorporation of 0.2% nano cellulose and 5.0 KGy gamma radiation doses application such as ultimate tensile strength (210% increment), bending strength (200% increment), elongation at break (12.5% reduction), impact strength (56% increment), Fourier Transform Infrared, scanning electron microscope, as well as water uptake test.

Impact of hemp woody core surface chemical modification on wettability of epoxyurethane composites

ABSTRACT Hemp woody core (HWC) that is a by-product of hemp industry was subjected to pre-treatment with alkali (mercerisation) and further functionalisation with epoxidised soybean oil (ESO) or (3-aminopropyl)triethoxysilane (APS). Mercerisation resulted in more developed surface area and rearrangement of fibrils into denser packing. FTIR spectroscopy analysis revealed the presence of hydrogen bonds of HWC with modifier in case of ESO application as well as hydrogen and Si-O-C covalent bonds in case of APS application. Two types of Si-containing epoxyurethanes were filled with 60% of HWC with different surface modification: the first polymer contained diglycidyl ether of bisphenol-A (DGEBA), while the second one contained ESO as an epoxy component. The investigation of the surface properties of composites found that the ones based on ESO epoxyurethane were more hydrophobic than their respective counterparts. Hydrophilicity was reduced by functionalisation of HWC providing a contact angle augment from 54°for DGEBA-containing sample with raw HWC to 86° for the one with oil modified HWC. The results of water uptake test showed that regardless of the matrix the composites reinforced with functionalised HWC exhibited about 40% less gain in weight at the saturation level than their analogues reinforced with untreated or alkali treated HWC.

Comparative Analysis of the Advantages and Disadvantages of Utilizing Spirulina-Derived Pigment as a Bio-Based Colorant for Wood Impregnator

The aim of this work was to examine the advantages and disadvantages of using spirulina-derived pigment as a bio-based colorant for wood impregnators. It investigated the effects of three different quantities of spirulina granules on the aesthetic properties and durability of a water-based wood impregnator. The impact of this environmental friendly pigment on the overall appearance of the coatings was estimated through colorimetric measurements and observations using an optical microscope. The durability of the coatings with varying amounts of spirulina was assessed by subjecting the samples to UV-B radiation and cyclic thermal shocks and analyzing them using infrared spectroscopy and colorimetric inspections. Furthermore, the influence of additive concentration on the coating’s barrier efficiency was examined through liquid resistance and water uptake tests. Finally, the scrub test was carried out to assess the effect of the spirulina pigment on the abrasion resistance properties of the protective layers. Ultimately, this study emphasized the remarkable coloration achieved through the use of the spirulina-based additive. However, the pigment derived from natural sources exhibited significant concerns associated with deterioration caused by UV-B radiation or the fading of the phycocyanin component found in spirulina. Thus, the work underscores the importance of implementing appropriate measures to safeguard the bio-based pigment from external factors such as temperature, solar radiation, and liquids.

Experimental analysis of the impact of ionic concentration and type on shale’s stability: dilute vs. concentrated salt solutions

ABSTRACT Wellbore instability in shale formations is one of the most bothersome problems leading to significant changes in shale’s petrophysical, mechanical, and chemical properties, and could cost billions of dollars annually. Drilling fluid’s ionic composition is one of the factors affecting wellbore stability. This paper investigates the impact of chemical osmosis, ionic diffusion, and diffusion osmosis on the stability of shale, identify the critical salt concentration, and examine the impact of ionic type and concentration on shale’s stability. Experimental methods include utilisation of two different shale cores (I and II), in which each core is cut into several samples, to conduct linear expansion and gravimetric measurement tests using different salt solutions (KCl, NaCl, and CaCl2) of various salt concentrations. Results show that the critical salt concentrations of shale I and II is 8 w/w%. Chemical osmosis is found to be a reliable method for water extraction out of shale if the critical salt concentration value is not surpassed. Beyond this value, ionic diffusion and diffusion osmosis in shale I and II were adversely affecting shale’s stability through swelling. The swelling and gravimetric ions and water uptake tests showed that shale is a leaky semi-permeable membrane, and that chemical osmosis could be jeopardised by ionic transport into shale. In this study, the cation type (Na+, K+, Ca+2) that makes up the salt was varied. The impact of cation type on the stability of shale was clear as the anion type was fixed. Since both cations and anions tend to diffuse into shale in the presence of a concentration gradient, it is proposed for future work to study the combined impact of cation and anion types on shale’s stability by varying the anion and cation types.

Utilization of Breadfruit (Artocarpus altilis) Peel Waste and Blood Clam Shell Waste (Anadara granosa) as Raw Materials for Glycerol-Plasticized Degradable Bioplastic Production

Nowadays, the world needs solutions to manage the ever-growing plastic waste problem. Plastics cannot decay easily in natural environment for example, PET took about 23 to 48 years to decay naturally in the environment. Therefore, it is urgently needed to find an alternative to these types of plastics, namely degradable plastics. One type of degradable plastic, called starch-based bioplastic can be made using starchy materials from Breadfruit peel. This, is in combination with Blood Clam shell – derived chitin nanowhiskers as reinforcer and glycerol as plasticizer. In this research, bioplastic is synthesized using starch extracted from Breadfruit (Artocarpus altilis) peel waste, reinforcing agent chitin nanowhisker (CNW) made from Blood Clam (Anadara granosa) shell waste, and glycerol as plasticizer. Furthermore, the plastic was tested according to general standard plastic tests including Tensile Strength, Water Uptake and Soil Burial test. Soil burial test results showed that in the period of less than 15 days, the bioplastic was completely decomposed. Water uptake test results showed that the bioplastic made from breadfruit peel starch and Blood Cam-derived CNW achieved water uptake numbers as high as 94,077 %, Tensile strength test showed that the bioplastic made from breadfruit waste starch and Blood clam-derived CNW of 0.0994 MPa was almost two times stronger than bioplastic made without the addition CNW of 0.0587 MPa and was also stronger than conventional plastics.

Improving corrosion resistance of BFRP bars by coating CNTs modified resin in simulated pore solution of seawater sea sand concrete

The corrosion of basalt fiber-reinforced polymer (BFRP) bars restricts their use in alkaline concrete structures. However, developing high-performance resin can improve the anti-alkaline corrosion of BFRP bars. This work investigates the alkaline resistance of BFRP bars by coating carbon nanotubes (CNTs) modified epoxy resin incorporating varying CNTs contents (0, 0.1, 0.3, and 0.5 wt%). The durability of untreated and treated BFRP bars with CNT-modified resin was evaluated using water uptake, transverse shear, and interlaminar shear tests. Scanning electron microscopy (SEM) and X-ray micro-computed tomography (micro-CT) were also used to observe the surface corrosion morphology and interior deterioration of BFRP bars, respectively, while Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were applied to analyze the resin deterioration of BFRP bars. It was found that CNTs modified resin can significantly improve the alkaline resistance of BFRP bars. After 180 d of immersion, the interlaminar shear strength (ILSS) retention of untreated BFRP bars is 31.8%, while it is 63.3, 75.0, 91.3, and 93.7% for BFRP bars treated with 0, 0.1, 0.3, and 0.5 wt% CNTs modified resin, respectively. The improvements in ILSS retention of BFRP bars treated with 0.5 wt% CNTs modified resin are 61.9% and 30.4% more than untreated and pure resin-treated BFRP bars, respectively. BFRP bars treated with 0.3 and 0.5 wt% CNTs modified resin exhibit insignificant resin hydrolysis and less porosity than untreated BFRP bars. The effective prevention of hydroxyl ions into the interior of BFRP bars and the enhancement of the anti-crack behavior of resin by CNTs are the leading causes of corrosion resistance improvement in BFRP bars. The outcomes of this study provide insights into using CNTs modified resin to improve the durability of BFRP bars in marine concrete structures.

Synergistic contribution of bio-based additives in wood paint: The combined effect of pigment deriving from spirulina and multifunctional filler based on carnauba wax

This work aims to reveal the synergistic behavior of two bio-based additives on the durability and protective behavior of a bio-based wood paint. The powder extract form spirulina was introduced as a natural pigment, while carnauba wax was used as a multifunctional filler. The impact of the two additives on the morphology of the coatings was investigated by scanning electron microscopy observations, while their role on the durability of the paint was assessed by exposing the samples to UV-B radiation and continuous thermal shocks. Infrared spectroscopy analysis, colorimetric inspections, adhesion test and scanning electron microscope observations were employed to investigate the impact of the synergic behavior of the bio-based additives. Furthermore, the role of the spirulina and wax powders on the barrier performance of the coatings was evaluated by liquid resistance test ad water uptake test. Finally, Buchholz hardness indentation test and the scrub test were employed to estimate the effect of the additives on the mechanical properties of hardness and abrasion resistance of the coatings. Ultimately, this work demonstrates the interesting synergy of spirulina and wax, able to provide an intense coloring and certain aesthetic features to the paint, to improve the water-repellent properties of the surface and to increase the abrasion resistance of the composite layer.

Fabrication of Helix aspersa Extract Loaded Gradient Scaffold with an Integrated Architecture for Osteochondral Tissue Regeneration: Morphology, Structure, and In Vitro Bioactivity.

Regeneration of osteochondral tissue with its layered complex structure and limited self-repair capacity has come into prominence as an application area for biomaterial design. Thus, literature studies have aimed to design multilayered scaffolds using natural polymers to mimic its unique structure. In this study, fabricated scaffolds are composed of transition layers both chemically and morphologically to mimic the gradient structure of osteochondral tissue. The aim of this study is to produce gradient chitosan (CHI) scaffolds with bioactive snail (Helix aspersa) mucus (M) and slime (S) extract and investigate the structures regarding their physicochemical, mechanical, and morphological characteristics as well as in vitro cytocompatibility and bioactivity. Gradient scaffolds (CHI-M and CHI-S) were fabricated via a layer-by-layer freezing and lyophilization technique. Highly porous and continuous 3D structures were obtained and observed with SEM analysis. In addition, scaffolds were physically characterized with water uptake test, micro-CT, mechanical analysis (compression tests), and XRD analysis. In vitro bioactivity of scaffolds was investigated by co-culturing Saos-2 and SW1353 cells on each compartment of gradient scaffolds. Osteogenic activity of Saos-2 cells on extract loaded gradient scaffolds was investigated in terms of ALP secretion, osteocalcin (OC) production, and biomineralization. Chondrogenic bioactivity of SW1353 cells was investigated regarding COMP and GAG production and observed with Alcian Blue staining. Both mucus and slime incorporation in the chitosan matrix increased the osteogenic differentiation of Saos-2 and SW1353 cells in comparison to the pristine matrix. In addition, histological and immunohistological staining was performed to investigate ECM formation on gradient scaffolds. Both characterization and in vitro bioactivity results indicated that CHI-M and CHI-S scaffolds show potential for osteochondral tissue regeneration, mimicking the structure as well as enhancing physical characteristics and bioactivity.

High hydrophobic silanized paper: Material characterization and its biodegradation through brown rot fungus.

Modifying natural polymers with silicones gives new possibilities for packaging products and waste management. In this study, the innovative papers produced were altered following the reaction of polysaccharides and organosilicon compounds. The susceptibility of the studied material to biodegradation caused by a brown-rot fungus was assessed. Strength properties by tensile strength and dynamic mechanical analysis and hydrophobic properties by water uptake test and water contact angle analysis were evaluated. Moreover, elemental analysis by ICP method was controlled. The durability against fungi and the hydrophobic properties were increased by the modification. The fungal decay resistance of the silanized paper was reduced by water storage, which allows for managing paper waste. Cellulose-based paper treated with starch-modified methyltrimethoxysilane showed potential as a packaging material due to its reduced water uptake. Possible application areas could be corrugated boxes, cellulose thermoformed products for electronics, and food packaging. However, the water-repellent effect is limited to short-term exposure in humid conditions.

Impact of High Concentrations of Cellulose Fibers on the Morphology, Durability and Protective Properties of Wood Paint

This work aims to reveal the effect of a high amount of cellulose fibers on the durability and protective behavior of a bio-based wood paint. The influence of the filler on the morphology of the coatings was investigated by scanning electron microscopy observations, while the durability of the paint was evaluated by exposing the samples to UV-B radiation and continuous thermal shocks. Infrared spectroscopy analysis, colorimetric inspections, adhesion tests and scanning electron microscope observations were employed to assess the role of the high concentrations of fillers in affecting the resilience of the acrylic matrix. Moreover, the impact of the filler on the barrier performance of the coatings was estimated using a liquid resistance test and a water uptake test. Finally, the mechanical properties of hardness and abrasion resistance of the layers were evaluated by means of the Buchholz Hardness Indentation test and the Scrub test. Ultimately, this study demonstrates the pros and cons of using large amounts of cellulose fibers as filler in wood paint: the work warns against the excessive use of these fibers, which need a threshold limit so as not to significantly change the coating’s structure and thereby weaken its protective properties.

Chitosan-polyaniline-TiO2 ternary nanocomposite coating as effective anti-corrosion material for low carbon steel in 3.5 wt% NaCl solution

The coating materials Polyaniline (PANi), Polyaniline-TiO2, and Chitosan-Polyaniline-TiO2 ternary nanocomposite (CPT) were separately synthesized by chemical oxidative polymerization with ammonium persulphate as an oxidant in a hydrochloride aqueous medium. The synthesized materials were characterized by FT-IR, XRD, SEM, and TEM. The FT-IR and XRD result adequately established the interaction between chitosan, PANi, and TiO2 NPs. Microstructural studies revealed significant variation in the morphologies of PANi, PANi-TiO2, and chitosan-polyaniline-TiO2 nanocomposite and embedment of TiO2 NPs in the polymer matrix. The coating materials PANi, PANi-TiO2, and CPT were mixed with epoxy resin (10%) and subsequently, cast on low carbon steel (LCS) using NMP as solvent and triethyl tetra amine as curing agent. The anti-corrosion properties of coated specimens in 3.5 wt.% NaCl solution was evaluated using EIS studies, PDP, Salt spray test, water uptake test, immersion test, and SEM. Results of corrosion tests revealed superior corrosion protection offered by CPT ternary nanocomposite coating to LCS in 3.5 wt % NaCl solution compared to PANi and PANi-TiO2 nanocomposite coatings.

Water absorption characterization of boron compounds-reinforced PLA/flax fiber sustainable composite

Biocomposites are widely used in construction, packaging, and automotive applications such as seatbacks, door panels, headliners, and dashboards, as well as industrial composting. The purpose of this study is to look into the effects of three different boron compounds (borax boric, acid combines, zinc borate, and ulexite) on the mechanical and microstructural properties of flax fiber/PLA biocomposites at different water uptake times. 7 different biocomposites were studied for this purpose: control, 3UF, 5UF, 3ZBF, 3BxBcF, 5BxBcF, and 5ZBF. Extrusion was used to create homogenous chopped flax fiber-reinforced PLA biocomposites, which were then injection molded. Alkali treatment on flax fiber surfaces was applied to improve interfacial adhesion between fiber and matrix. Water uptake tests were performed at room temperature for soaking times of 24, 50, 168, 240, 330, 480, 550, 600, and 750 h. The addition of boron compounds increases water gain from 4.4 % to 6.1 %, according to sorption results. The tensile elongation at break values of the composites increased slightly after short-term water absorption. SEM images showed that alkali-treated flax fibers and boron compounds dispersed uniformly in the PLA matrix. After 750 h of immersion, the addition of boron fillers to PLA/flax composite increased Young's Modulus and flexural modulus by about 50 % and 72 %, respectively, in comparison to the control composite sample. The addition of boric acid: borax combines into the PLA/flax composite slowed the rate of decline in tensile and flexural strength after various immersion times. Finally, using MINITAB software, the experimental results were subjected to a one-way analysis of variance (ANOVA).

The Effect of Taro Tuber Starch (Colocasia esculenta (L.) schott) Addition to Characteristic of Biodegradable Plastic with PVA Polymer and Calcium Carbonate (CaCO3) Filler

The preparation of biodegradable plastics based on polyvinyl alcohol (PVA)-taro starch as an alternative to synthetic plastics has been conducted. The aim of this research was to identify the effect of taro starch composition on the production of biodegradable plastic and their characteristics in an aquatic environment. The solution casting method was used to produce biodegradable plastic. PVA was dissolved in hot distilled water, and taro starch (0; 0.5; 1.5; 2.5; and 3.5 g) was dissolved in another chamber filled with distilled water, glycerol and citric acid. Both solutions were mixed together and CaCO3 was then added. The mixture was casted on acrylic plates while biodegradable plastic without starch was used as a control. Characteristic of Biodegradable plastic and it’s properties were examined by Fourier Transform Infra Red (FTIR), water uptake, and moisture absorption test. While the biodegrability of the sample were tested in river water media in the laboratory. The results showed that the wave number at 1698-1712 cm-1, indicating that the cross-linking between PVA and the starch occured. Water uptake and moisture absorption tests showed that all of the biodegradable plastic varieties produced were hydrophilic. The biodegradation test showed that the largest degree of decomposition was reached by the PVA-starch 3.5 g variety which was 80.33%. Thus, the more starch on biodegradable plastic, the more biodegradation achieved.

Reliability of chemical osmosis as a practical method to extract water out of shale and promote shale’s mechanical stability

Wellbore instability in shale formations is one of the most bothersome problems leading to significant changes in shale’s petrophysical, mechanical, and chemical properties, and could cost billions of dollars annually. Drilling fluid’s ionic composition is one of the factors affecting wellbore stability. This paper investigates the impact of chemical osmosis, ionic diffusion, and diffusion osmosis on the stability of shale, identify the critical salt concentration, and examine the impact of ionic type and concentration on shale stability. Experimental methods include utilization of shale I and II through linear expansion and gravimetric measurement tests using different salts. Results show that the critical salt concentration in shale I and II is 8 w/w%. Chemical osmosis is found to be a reliable method for water extraction out of shale if critical concentration value is not surpassed. Beyond this value, the ionic diffusion and diffusion osmosis in shale I and II were adversely affecting shale’s mechanical and chemical stability. The swelling and gravimetric ions and water uptake tests showed that shale is a leaky semi-permeable membrane, and that chemical osmosis could be jeopardized by ionic transport into shale. However, the water transport impact on changes in the thickness of diffuse double layer of clay needs to be investigated. The impact of temperature on water and ions transportation into shale needs to be examined to reflect in-situ conditions. In this study, the cation type that makes up the salt was varied while the anion type was fixed. Since both cations and anions tend to diffuse into shale in the presence of a concentration gradient, it is recommended to vary the anion type to study the combined impact of cation and anion type on shale stability.

Multi-component polymeric membranes based on acrylamide monomers for fuel cells

The preparation, characterization, and evaluation of properties of proton exchange membranes (PEMs) for application in fuel cells (FCs) based on non-fluorinated hydrocarbons are described in this paper. A new class of membranes was synthesized by radical copolymerization, in aqueous medium, using low-cost monomers. The copolymers were constituted of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as proton-conducting groups, hydroxyl ethylacrylamide (HEA) as crosslinking sites and styrene and N-isopropyl-acrylamide (NIPAM) as hydrophobic domains. The membranes were obtained by crosslinking the copolymers with glutaraldehyde in acidic medium under different conditions. The copolymers were characterized by infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (1H NMR), size exclusion chromatography (SEC) and thermogravimetric analysis (TGA). The membranes were also characterized by FTIR, which pointed out the changes resulting from the reaction with glutaraldehyde. TGA analyzes allowed to evaluate the thermal stability of the membranes in temperature ranges consistent with the use in FCs. The water uptake tests showed greater water absorption for samples without or with a low percentage of hydrophobic component. In addition, higher crosslinking agent content, acidification and higher curing temperatures led to a reduction in the degree of swelling. For the conductivity measurements, only the samples with NIPAM showed adequate stability to be submitted to the previous hydration treatment. As a result, these membranes presented higher conductivity values, close to those of commercial membranes. In general, membranes with more conductive groups in the composition, higher hydration and less crosslinks showed better conductivities. Finally, the set of samples with the best results was evaluated in oxidative degradation tests. In summary, the results presented allowed an evaluation of the adjustment of the properties of PEMs through the control of crosslinking and the formulation of the membranes.

The impact of vacuum pressure on the effectiveness of SiO2 impregnation of spruce wood

Wood is a widely used construction material that has many advantageous properties. However, it suffers from weaknesses such as low-dimensional stability and low durability in humid environments. These issues are associated with the porous vascular structure of wood that leads to a high water uptake capacity. This research aims to reduce the water uptake capacity of spruce wood by dip-coating samples in an aqueous colloid of silicon dioxide (SiO2) nanoparticles. SiO2 is a dense ceramic material with good chemical stability. It is readily available and affordable, making it an excellent candidate for this application. This study investigates the effect of SiO2 impregnation on the physico-mechanical properties of spruce wood. Density measurements, water uptake tests, microscopy examination, thermogravimetric analysis, and dynamic mechanical analysis were conducted on non-treated and SiO2-treated spruce wood samples. Quantitative and qualitative analyses demonstrated that SiO2 impregnation performed under higher vacuum pressure was more effective compared to the atmospheric condition and exhibited a greater presence of SiO2 in the wood’s vascular system. SiO2 impregnation under vacuum pressure demonstrated an effective increase in the density of the wood. It also reduced the porosity, which led to a significant reduction in the water uptake of the spruce wood. The analysis of the wood viscoelastic properties revealed that SiO2 impregnation under atmospheric and vacuum conditions triggered two different reinforcing mechanisms. The results showed that a significant improvement of the spruce wood storage and loss moduli could be achieved when impregnation was performed at the highest vacuum pressure of − 90 kPa.