Improved Water Resistance Research Articles

Preparation of green and durable magnesium oxysulfate cement using sewage sludge ash: Physical properties, microstructure, and leaching behavior

The aim of this study was to explore the application of sewage sludge ash (SSA) as a substitute for light-burnt magnesium oxide (LBM) in the preparation of magnesium oxysulfate cement (MOSC), in order to achieve the harmless treatment of SSA and improve the performance of MOSC. By adjusting the SSA dosage, a series of MOSC samples were prepared, and their setting time, compressive strength, water resistance, and heavy metal leaching rates were then systematically evaluated. Additionally, their crystal phase composition, relative content, and microstructure were characterized using XRD, TGA, FTIR, and SEM in order to elucidate the mechanism by which SSA affects the properties of the MOSC. The results indicate that the addition of SSA prolongs the setting time of MOSC and reduces its compressive strength. However, pozzolanic SiO2 in SSA can hydrate with MgO to form magnesium-silicate-hydrate gel, effectively improving the water resistance of MOSC. In particular, when SSA replaces 30 % of LBM, MOSC not only meets the heavy metal leaching standards for Class IV surface water in China, but also has a compressive strength of up to 67 MPa and a significant improvement in water resistance by 44 %. This study not only opens up new avenues for the harmless treatment of SSA, but also provides scientific basis and practical reference for optimizing the water resistance of MOSC.

Production of bioplastic films from wild cocoyam (Caladium bicolor) starch

This study tackles the pressing environmental challenges resulting from the rapid and ongoing use of conventional plastics by investigating biodegradable alternatives derived from wild cocoyam starch. The bioplastics developed from various formulations, incorporating gelatin, glycerine, vegetable oil, and vinegar, were systematically evaluated for their mechanical, chemical, microstructural and biodegradability properties. The addition of glycerine and gelatin enhanced the moisture content and flexibility of the films while vegetable oil improved water resistance, reducing water absorption. Th sample that contains 3 g of gelatin and 3 ml of glycerine exhibited the best overall performance with a tensile strength of 6.5 MPa and an elongation at break of 77 %. This sample also achieved an impressive biodegradation rate of 70 % within 7 days. Scanning Electron Microscopy revealed a uniform and smooth morphology, while Fourier Transform Infrared Spectroscopy confirmed the presence of key functional groups responsible for the material's performance. These results establish wild cocoyam starch as a promising resource for producing biodegradable bioplastics with considerable potential in various industries, particularly in packaging and agricultural applications. The excellent mechanical properties and biodegradability of the materials along with its natural abundance, offer an eco-friendly solution to the plastic waste problem. The study also opens new avenues for optimizing bioplastic formulations to enhance specific properties like thermal stability and moisture resistance, further broadening their practical applications. This research contributes to the sustainable materials landscape and represents a step toward reducing reliance on fossil-based plastics, advancing the global effort to mitigate environmental pollution.

Weather-Resistant Organosilicate Coatings with Improved Water Resistance

Weather-Resistant Organosilicate Coatings with Improved Water Resistance

Improving Water Resistance and Mechanical Properties of Crosslinked Waterborne Polyurethane Using Glycidyl Carbamate

Waterborne polyurethane (WPU) often suffers from poor water resistance and mechanical properties due to hydrophilic emulsifiers. To address these issues, this study introduces glycidyl carbamate (GC) as a crosslinker to improve WPU performance. Three types of GC were synthesized using aliphatic, cycloaliphatic, and aromatic isocyanates, respectively. The crosslinked network was established through a reaction between the epoxide group of GC and the carboxylic acid and amine groups of WPU. Among these, the WPU film utilizing aromatic isocyanate-based GC exhibited the highest crosslink density, modulus, hardness, and water resistance, due to the rigidity of the aromatic molecular structure. However, the film displayed excessive brittleness, resulting in reduced tensile strength, along with yellowing typically associated with aromatic compounds. The WPU crosslinked with cycloaliphatic GC demonstrated the next best mechanical properties and water resistance, with a 2.7-fold increase in tensile strength, a 1.5-fold increase in hardness, and a 66% reduction in the water swelling ratio compared to neat WPU. This study presents a novel and effective strategy to enhance the water resistance and mechanical properties of WPU films, making them suitable for advanced coating applications.

Effect of Phosphoric Acid and Soluble Phosphate on the Properties of Magnesium Oxychloride Cement.

This study investigates the effects of phosphoric acid (H3PO4), potassium dihydrogen phosphate (KH2PO4) and sodium dihydrogen phosphate (NaH2PO4) admixtures on the setting time, compressive strength and water resistance of magnesium oxychloride cement (MOC). MOC samples incorporating different admixtures are prepared, and their hydration products and microstructures are studied via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that the addition of H3PO4, KH2PO4 and NaH2PO4 reduces the initial and final setting times and decreases the compressive strength. However, the compressive strength of MOC is higher than 30.00 MPa with the addition of 2.0 wt.% phosphoric acid and its phosphate after 14 days of air curing. The water resistance of modified MOC slurries is significantly improved. The softening coefficient of MOC with 2.0 wt.% H3PO4 is 1.2 after 14 days of water immersion, which is 3.44 times higher than that of the neat MOC. The enhancement in water resistance is attributed to the formation of amorphous gel facilitated by H3PO4, KH2PO4 and NaH2PO4. Furthermore, the improvement in water resistance is manifested as H3PO4 > KH2PO4 > NaH2PO4.

The effect of graphene properties on the extrusion of a shape memory epoxy vitrimer

Thermoset polymers exhibit very appealing mechanical and functional properties. Direct ink writing (DIW) could open new possibilities in the design and fabrication of intricate thermoset parts, but it often requires the use of additives such as fumed silica or nanoclays to modify the rheology of uncured epoxies. However, relatively large concentrations are usually needed what can be detrimental to properties. Graphene-derived additives are an appealing alternative, but we need to understand the key physicochemical characteristics that define an optimum graphene rheology modifier. Here we compare the effect of three different carbon fillers on the viscoelastic response of a reprocessable epoxy vitrimer with shape memory capabilities, graphene oxide (GO), reduced graphene oxide (rGO), and graphene powder (GP), and assess the effect of their chemistry and morphology. The analysis shows that large (∼20 μm in size) rGO flakes enable the formation of strong, printable gels, through Van der Waals interactions and physical entanglement. The vitrimer could be successfully printed by incorporating 5 wt% of rGO. The printed parts exhibit tensile strengths (30–60 MPa), moduli (2–3 GPa), strength recovery after reprocessing (∼80 %), shape-memory properties comparable to the pure epoxy, and improved water resistance due to the introduction of hydrophobic rGO.

Enhancing moisture-resistance in polyimide aerogels: A novel hydrophobic modification approach with ortho-positioned long-chain barriers

Polyimide (PI) aerogels possess significant potential for various applications due to their outstanding mechanics and thermal insulation. However, a major drawback of these aerogels is their susceptibility to moisture, which not only compromises their insulative performance but also leads to an increase in weight. To address this issue, we have developed a moisture-resistance technique by incorporating a long-chain hydrophobic barrier at the ortho position relative to the imide groups to enhance the moisture-resistance of the PI aerogels. This approach involved using a series of diamines with hydroxyl groups strategically located at the ortho position of imide groups as reactants. The resulting PI aerogels demonstrated a significant improvement in water resistance, reducing water-uptake to merely one-tenth of that recorded in unmodified samples. Furthermore, the effectiveness of this hydrophobic modification was validated through molecular dynamics simulations, which indicated a diffusion coefficient of 4.41 × 10−11 m2/s after modification. These findings represent a considerable advancement in developing effective methods for hydrophobic modification of PI aerogels, with potential applications in aerospace, electronic communications, and environmental protection.

Influence of hot-pressing temperature and density on the physical and mechanical properties of bamboo scrimber

Bamboo scrimber (BS) has been widely used as a high-performance engineering composite in construction and outdoor applications, typically employing a thermosetting adhesive that requires hot-pressing. Previous studies have focused on the effects of resin content and BS curing temperature, often overlooking the self-bonding of bamboo during the hot-pressing process. This study investigated the impact of hot-pressing temperature and density on the physical and mechanical properties of BS containing phenol–formaldehyde resin, with a particular focus on regulating BS self-bonding by adjusting these parameters. The study also examined the effects on the chemical composition and pore structure of BS. The results showed that increasing the hot-pressing temperature from 140 to 180 °C broke unstable bonds in the hemicellulose, cellulose, and lignin components of the BS, leading to new crosslinks through dehydration and thermal degradation reactions. This process enhanced self-bonding, improved water resistance, and resulted in different surface colors. Raising the density from 0.9 to 1.3 g/cm3 made the density distribution of BS more uniform and reduced the size and number of internal pores. These characteristics promoted interfacial bonding and impeded water flow through the material, thereby enhancing its water resistance and mechanical properties. This study elucidates the mechanism behind the performance enhancement of BS and offers insights for its low-cost and environmentally friendly production.

Advancing sustainable molded packaging: Integrating silica aerogel into recycled paper pulp for the fabrication of thermally and mechanically stable superhydrophobic composites

In recent years, the growing demand for sustainable packaging has significantly fueled the quest to explore novel approaches that enhance the applicability of renewable alternatives. This study leverages the unique properties of silica aerogel (SA) to address the limitations of traditional molded pulp products. By integrating SA into recycled paper pulp (RP), we aimed to improve water resistance, thermal stability, and mechanical properties. Composites were prepared with varying SA concentrations (1–10 %). Contact angle measurements showed enhanced hydrophobicity, with RP/SA3 % achieving a contact angle of 152.09°, compared to 122.39° for neat RP. The tensile index (TI) of RP/SA composites with 3 % SA increased by 21.09 % compared to neat RP, indicating better mechanical strength. Thermal conductivity significantly decreased, with RP/SA10 % reducing from 0.155 W m−1·K−1 in neat RP to 0.088 W m−1·K−1, a 43.2 % improvement in thermal insulation. Additionally, composites with 1 % and 3 % SA maintained high biodegradability, showing over 50 % degradation after six weeks in soil. These results suggest that incorporating SA into RP composites enhances their functionality without compromising biodegradability, offering a promising solution for sustainable packaging. As regulatory bodies emphasize resource management and waste reduction, the potential of these innovative and environmentally friendly packaging solutions becomes increasingly significant.

The ancient glass decoloration technology based on the Fe-Mn redox pairs revived to improve the chemical stability of Fe2O3-containing borosilicate glass for medical application

MnO has been used for the decoloration of glasses containing iron oxide impurity since ancient times, based on the oxidation-reduction of Fe-Mn redox pairs (Fe2++Mn3+→Fe3++Mn2+). In this work, it was evidenced that a combinative addition of Fe2O3 and MnO into borosilicate glasses for pharmaceutical packaging application induced the above reaction and improved the water resistance of glass. As a comparative study, the structure of glasses with the inclusion of either MnO or Fe2O3 and both of them as well as the valence, coordination of Fe and Mn ions in the glasses were fully investigated by using FTIR, Raman, NMR, EPR, PL and UV–Vis–NIR spectroscopy. It was concluded that the single addition of Fe2O3 or MnO had a similar depolymerization effect on the glass structure, while the co-addition of Fe2O3 and MnO exhibited a synergistic effect, which led to the increase of glass network connectivity due to oxidation-reduction of Fe/Mn redox pairs and consequently the improvement of water resistance of the glasses.

Ionized Carboxyl Protonation Strategy to Improve Water Resistance of Carboxymethyl Cellulose-Based Ultraviolet-Shielding Films

Ionized Carboxyl Protonation Strategy to Improve Water Resistance of Carboxymethyl Cellulose-Based Ultraviolet-Shielding Films

Enhancement of chitosan-based film physicochemical and storage properties by interaction with proanthocyanidin and natural deep eutectic solvent

Deep eutectic solvent (DES) has been recognized as a promising plasticizer for the preparation of biodegradable food packaging films. In addition, DES-plasticized chitosan (CS) films could also serve as a favorable carrier for loading active components. In this work, a ternary composite film was fabricated by plasticizing chitosan with DES and the active ingredient proanthocyanidin (PA) was used as a cross-linking agent. The incorporation of PAs significantly enhanced the toughness, elasticity, and hydrophobicity of the ternary CS-DES-PA composite films. It achieved antioxidant and bacteriostatic functions. In particular, the ternary CS-DES-PA composite films had a thickness of 0.16 ± 0.01 μm, a tensile strength of 2.63 ± 0.48 MPa, and an elongation about 73.22 %. They also have improved water resistance, UV blocking, with a high-water contact angle of 88.4° and a low water swelling of 5 % on the surface of the film. Meanwhile, the PAs in the film could slow down the browning of litchi fruits. This ternary blended film (CS-DES-PA) achieves better compatibility of the active ingredient in the film-forming substrate. It also provides a green and biodegradable packaging material for food packaging.

Addition of Coffee Waste-Derived Plasticizer Improves Processability and Barrier Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-Natural Rubber Bioplastic.

This study aimed to develop a value-added bio-based polymer product for food packaging. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising bioplastic with limitations in processability and brittleness, which our group previously addressed by incorporating high-molecular-weight natural rubber (NR) compatibilized with peroxide and coagent. Yet, processability in an industrial setting proved difficult. Coffee oil epoxide (COE), a waste-derived plasticizer, was incorporated into the PHBV/NR/peroxide/coagent matrix via extrusion, and properties of resulting sheets were evaluated. COE incorporation significantly decreased the oxygen and water permeability of the PHBV/NR sheets. Maximum degradation temperature Tpeak (°C) increased by ~4.6 °C, and degree of crystallinity decreased by ~15.5% relative to pristine PHBV, indicating good thermal stability. Melting (Tm) and glass transition temperatures (Tg) of the PHBV/NR blend remained unchanged with COE incorporation. X-ray diffraction (XRD) revealed ~10.36% decrease in crystal size for the plasticized blend. Energy-dispersive X-ray analysis (EDAX) and scanning electron microscopy (SEM) confirmed good dispersion with no phase separation. The water uptake capacity of the plasticized blend was reduced by 61.02%, while surface contact angle measurements showed improved water resistance. The plasticized PHBV sheet shows promise for environmentally friendly packaging films due to its high thermal stability, effective barrier properties, and industrial scalability.

Impact of Silver Nanoparticle Treatment and Chitosan on Packaging Paper's Barrier Effectiveness.

In this study, a comparative analysis of silver nanoparticles treatment and chitosan coating on packaging paper barrier properties was carried out. In order to examine the water, grease, and antibacterial barrier properties of silver nanoparticle-treated and chitosan-coated laboratory-obtained paper samples, a mixture of bleached softwood and hardwood celluloses was used. In order to conduct the comparative analysis SEM, water contact angle, Cobb60, and Kit tests were carried out on a cellulose sample, and four paper samples (three of them treated with silver nanoparticles-1, 2, and 3 mL/20 cm2 or chitosan coated-0.5, 1, and 2 g/m2) together with the inhibition activity against nine Gram-positive and Gram-negative bacteria, yeast, and fungal strains. The study found out that increasing the silver nanoparticle treatment and chitosan coating led to improved water resistance, while grease resistance was improved only for chitosan coated paper samples. Additionally, paper treated with 3 mL/20 cm2 of silver nanoparticles had the highest antibacterial protection (81.6%) against the Gram-positive bacterium Staphylococcus aureus, followed by Gram-negative Escherichia coli (75.8%). For the rest of the studied microorganisms, the average efficiency of the treated paper was 40.79%. The treatment of the paper with 1 and 2 mL/20 cm2 of silver nanoparticles was less effective-27.13 and 39.83%, respectively. The antibacterial protection of 2 g/m2 chitosan-coated paper samples was the most effective (average 79%) against the tested bacterial, yeast, and fungal strains. At 1 and 0.5 g/m2 chitosan coatings, the efficiency was 72.38% and 54.67%, respectively. Gram-positive bacteria, yeasts, and fungal strains were more sensitive to chitosan supplementation.

Chitosan Extracted from the Biomass of Tenebrio molitor Larvae as a Sustainable Packaging Film.

Waste from non-degradable packaging materials poses a serious environmental risk and has led to interest in developing sustainable bio-based packaging materials. Sustainable packaging materials have been made from diverse naturally derived materials such as bamboo, sugarcane, and corn starch. In this study, we made a sustainable packaging film using chitosan extracted from the biomass of yellow mealworm (Tenebrio molitor) shell waste. The extracted chitosan was used to create films, cross-linked with citric acid (CA) and with the addition of glycerol to impart flexibility, using the solvent casting method. The successful cross-linking was evaluated using Fourier-Transform Infrared (FTIR) analysis. The CA cross-linked mealworm chitosan (CAMC) films exhibited improved water resistance with moisture content reduced from 19.9 to 14.5%. Improved barrier properties were also noted, with a 28.7% and 10.2% decrease in vapor permeability and vapor transmission rate, respectively. Bananas were selected for food preservation, and significant changes were observed over a duration of 10 days. Compared to the control sample, bananas packaged in CAMC pouches exhibited a lesser loss in weight because of excellent barrier properties against water vapor. Moreover, the quality and texture of bananas packaged in CAMC pouch remained intact over the duration of the experiment. This indicates that adding citric acid and glycerol to the chitosan structure holds promise for effective food wrapping and contributes to the enhancement of banana shelf life. Through this study, we concluded that chitosan film derived from mealworm biomass has potential as a valuable resource for sustainable packaging solutions, promoting the adoption of environmentally friendly practices in the food industry.

Development of novel sustainable biocomposite from polycaprolactone and Sesbania rostrata fiber

AbstractAn efficient method to accelerate the use of polymer composites is to focus on their development as environmentally friendly materials that can naturally break down without causing any harm to the ecosystem. Hence, the primary aim of this study is to develop a biocomposite material through the fusion of Sesbania rostrata (SRF) bark fibers and the polycaprolactone (PCL) biopolymer. Various percentages (10, 15, 20, and 25 wt.%) of untreated and sodium bicarbonate‐treated SRF were incorporated into polycaprolactone to create the biocomposite samples. The composite panels were made using the compressing molding technique. Several tests were performed on the samples, such as mechanical, thermal, water absorption, wear, and morphological tests. Research has demonstrated that the strength of biocomposites composed of 20% chemically treated SRF and PCL is superior to that of other mixed materials. The thermal properties of the biocomposite remained unchanged when untreated fibers were included, but they improved when treated fibers were included. Higher water absorption properties are attributed to an increased fiber volume fraction in the biocomposites, while chemically treated fibers exhibit a notable improvement in water resistance. The wear test results indicate that the weight loss of the biocomposites is mainly influenced by the contact temperature and adhesion between the SRF surface and the PCL matrix. When examining the fractured biocomposites with a scanning electron microscope (SEM), it becomes evident that the primary reasons for failure are fiber pull‐out, debonding, and agglomeration.Highlights SR Natural fiber is chemically treated by eco‐friendly sodium bicarbonate. The treated SRF‐reinforced composites had best mechanical property. The treated SRF‐reinforced composites showed less water absorption. The composite mechanical and thermal properties had dropdown at 25 wt.% SRF. The addition of SRF reduced the weight loss of composites on wear test.

Improvement of water resistance for natural rubber/nanocellulose composites

Natural rubber/cellulose nanofiber (NR/CNF) composites exhibit improved dry tensile properties compared with neat NR sheets. However, the presence of hydrophilic CNFs in the composites causes low water resistance, resulting in high water content and low tensile strength when the composites are soaked in water at 70 °C for 7 d. Herein, water-resistant NR/CNF composites were developed by adding zinc methacrylate or aluminum acrylate, and the oven-dried NR/CNF/additive materials were counterion-exchanged with 0.1 M NH4OH. X-ray fluorescence analysis of the composite sheets indicates the reasons and mechanisms for the improved water resistance of the composites prepared with the tested additives by post-counterion exchange.

Revealing La doping activation or inhibition of crystal facet effects in Co3O4 for catalytic combustion and water resistance improvement

It was challenging to enhance the catalytic activity and water resistance of transition metal oxides in the CH4 treatment process. Here, La with large atomic radii was doped onto Co3O4 on the (110), (111) and (100) crystal facets, respectively, and successfully doped into the (110) and (100) lattices, but accumulation occurs on the (111) crystal surface. Doping La into the Co3O4 lattice achieved a dual excitation effect for surface optimization and structural defects, causing lattice expansion, enhancing the electrophilicity of the O atoms in the vicinity of La, and significantly stimulating the Co-O bond. This significantly improved reactive oxygen species content, CH4 adsorption capacity, and gaseous oxygen activation and replenishment capability for higher catalytic activity. Conversely, the (111) facet with accumulated La showed an opposite trend. Meanwhile, La doping effectively improved the stability of Co3O4 and weakened its hydrophilicity, which effectively enhanced its water resistance. This research provided a viable strategy for designing high-performance and water-resistant Co3O4-based catalysts.

Fabrication and characterization of Karaya gum-based films reinforced with bacterial nanocellulose stabilized valerian root extract Pickering emulsion for lamb meat preservation

A novel biodegradable film was fabricated by incorporating bacterial nanocellulose stabilized valerian root extract (VRE) Pickering emulsion into karaya gum with better antioxidant and antibacterial properties for lamb meat preservation. The valerian root extract Pickering emulsion (VPE) exhibited 98 ± 1.84 % encapsulating efficiency and excellent physical stability with an average particle size of 274.6 nm. The incorporation of VPE-5 into the film matrix increased its elongation at break (EAB), and improved water resistance and barrier properties against oxygen, water vapor, and UV light. Moreover, the antioxidant and anti-bacterial properties against S.aerous and E. coli were also improved based on VPE-5 concentration. The SEM images showed a uniform distribution of VPE-5 while FTIR and XRD revealed its compatibility with karaya gum, which improved its thermal stability. The active films showed a significant preservative effect by reducing the pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), and total viable count (TVC) value of lamb meat and maintained its texture and color during the storage period of 9 days at 4 °C. These results demonstrated the inclusion of VPE-5 into Karaya gum was a promising technique and offers a great potential application as a bioactive material in food packaging.

A novel seaweed-based biodegradable and active food film to reduce freezer burn in frozen salmon

The imperative to replace conventional plastic food packaging has led to the development of edible and biodegradable alternatives. This study has formulated an effective packaging solution for the preservation of frozen salmon. Alginate films were prepared by integrating ethanolic extracts from two edible seaweeds, Sargassum muticum and Grateloupia turuturu. The optical and mechanical properties of the films, as well as their effectiveness in preserving frozen salmon over a 6-month period at −18 °C, were assessed and compared to other alginate and synthetic plastic films. The quality parameters of the final product were also assessed. Films incorporating Grateloupia extract exhibited a 34% reduction in thickness and 51% lower moisture content when compared to alginate. Meanwhile, those containing Sargassum extract demonstrated improved water resistance, with a 11% decrease in solubility. The seaweed-incorporated films demonstrated gradual biodegradation over time. Samples packaged with these films displayed a substantial decrease in colour changes, ranging from 58% to 64%, compared to commercial plastic film packaging. This enhanced protection against freezer burn is likely due to the presence of lipid-derivate compounds in the Grateloupia extract. The findings of this study suggest the potential use of alginate-based films incorporated with Grateloupia and Sargassum extracts as edible and biodegradable packaging for frozen fish, offering a sustainable and improved alternative to synthetic plastic films.