Improved Water Resistance Research Articles

Green fabrication of thermally cross-linkable 2-hydroxypropyl-β-cyclodextrin/ poly(acrylic acid)/poly(vinyl alcohol) nanofibrous membrane for effective removal of levofloxacin hydrochloride

Nanofibrous membranes are often obtained by electrospinning of polymer solutions. Because organic solvents are usually poisonous, it is desirable to develop green electrospinning for wide application of nanofibrous membranes. In the present research, water-soluble 2-hydroxypropyl-β-cyclodextrin, poly(acrylic acid) and poly(vinyl alcohol) were used as raw materials to prepare nanofibrous membranes by electrospinning of their aqueous solutions. The pristine membranes were subsequently crosslinked by thermal treatment in order to improve water resistance of membranes. The obtained membranes were used as adsorbents for removal of levofloxacin hydrochloride from aqueous solutions. The adsorption amount of levofloxacin hydrochloride increased with the content of 2-hydroxypropyl-β-cyclodextrin in the electrospinning solution because the cavity of 2-hydroxypropyl-β-cyclodextrin could capture levofloxacin hydrochloride by inclusion complexation. The adsorption of levofloxacin hydrochloride achieved equilibrium within 12 h and the maximum adsorption capacity was 100.8 mg/g at 298 K. Thermodynamic parameters suggested that the adsorption process was spontaneous and endothermic with increased degree of freedom at the solution/membrane interface. The adsorption mechanism was related to electrostatic attraction, hydrogen bonding and inclusion interactions. Moreover, the membrane still exhibited relatively stable adsorption capacity after five adsorption/desorption cycles. The current study presented a facile and green approach for preparing nanofibrous membranes with excellent adsorption performance for levofloxacin hydrochloride from aqueous solutions.

Improving water resistance property of starch straw by synergistic effects of chemical crosslinking, physical barrier, and surface modifications

AbstractStarch straws are developed by focusing on improving the critical weakness of all starch‐based materials: moisture sensitivity. Various technologies including blending (with hydrogel carrageen), chemical crosslinking (using citric and boric acids, and furfural), physical barrier (using talc), and surface modifications (by adding stearic acid, or hot oxalic acids) are evaluated, and then synergized in this study. The materials and products are characterized by Fourier transform infrared spectroscopy, contact angle, mechanical properties, water solubility and water absorption. All the trends of individual modification are similar to previous work but it was found that the influence of some modifications on the extruded straws was significantly different from that of the casting films reported previously since extrusion with high shear stress can destroy chemical and physical crosslinking or network formed. It was found that there was a maximum acid content to improve the water sensitivity since the excessive amount of acid could degrade starch and have more damage to the crosslinking during extrusion, resulting in decreasing mechanical properties and increasing solubility. On the other hand, some synergic functions, like crosslinked by additional citric acid and surface treatment by hot oxalic acid, were observed. The promising starch straws are developed based on synergic methodologies, in which typical samples were prepared by crosslinking using citric (1 w%), boric (2 w%), talc (3 w%), and stearic acids (1 w%) and treated with hot oxalic acids for 2 s. The optimized straw can be smoothly processed, reduced water absorption significantly (55.3%), and mechanical properties (modulus) increased about 54% compared with neat starch one after being immersed in water at room temperature (25°C) for 20 min. This synergic strategy provides a useful guideline for developing starch‐based materials with low moisture sensitivity.

Fabrication, Characterization and Permeation Studies of Ionically Cross-linked Chitosan/Kaolin Composite Membranes

This paper presents the successful preparation of porous membranes based on chitosan with enhanced mechanical, thermal and chemical properties applicable in water treatment field. Herein, chitosan/kaolin composite membranes with a cross-linking agent and a porogen were prepared using the solvent casting method. The characterization of the as-fabricated membranes indicated that the combined effect of kaolin as reinforcing agent, polyethylene glycol as pore former and citric acid as cross-linker in a chitosan matrix showed a significant influence on the membrane properties. The results indicated that the incorporation of a hydrophilic porogenic reagent into the collodion in addition to providing a porous morphology makes it possible to obtain a more hydrophilic membrane, and thus induces an increase in the pure water permeability. The cross-linked membranes exhibited an improved water resistance, better thermal and mechanical properties as compared to neat chitosan films. The cross-linked membranes had a mean pore size of 50 nm falling in the range of ultrafiltration. Their functional properties were determined in terms of pure water filtration and molecular weight cut-off tests.

Cu Species-Modified OMS-2 Materials for Enhancing Ozone Catalytic Decomposition under Humid Conditions.

Manganese oxide octahedral molecular sieves (OMS-2) exhibit an excellent performance in ozone catalytic decomposition in dry atmosphere conditions, which however is severely limited by deactivation in humid conditions. Herein, it was found that the OMS-2 materials modified with Cu species could obviously improve both the ozone decomposition activity and water resistance. Based on the characterization results, it was found that these CuOx/OMS-2 catalysts exhibited dispersed CuOx nanosheets attached and located at the external surface accompanied with ionic Cu species entering the MnO6 octahedral framework of OMS-2. In addition, it was demonstrated that the main reason for the promotion of ozone catalytic decomposition could be ascribed to the combined effect of different Cu species in these catalysts. On the one hand, ionic Cu entered the MnO6 octahedral framework of OMS-2 near the catalyst surface and substituted ionic Mn species, resulting in an enhanced mobility of surface oxygen species and formation of more oxygen vacancies, which act as the active sites for ozone decomposition. On the other hand, the CuOx nanosheets could serve as non-oxygen vacancy sites for H2O adsorption, which could alleviate the catalyst deactivation to some extent caused by the occupancy of H2O on surface oxygen vacancies. Finally, different reaction pathways for ozone catalytic decomposition over OMS-2 and CuOx/OMS-2 under humid conditions were proposed. The findings in this work may shed new light on the design of highly efficient catalysts for ozone decomposition with improved water resistance.

Development of a strong and conductive soy protein adhesive by building a hybrid structure based on multifunctional wood composite materials

In this study, a strong and multifunctional soy protein adhesive was designed and developed. It was then combined with wood units to prepare a clean and electromagnetic shielding wood-based panel via simple hot press. Specifically, bio-based raw material was prepared by grafting pyrrole (PY) and dopamine hydrochloride (DOPA) in sequence on to soy protein isolate (SPI), and then combined with AgNO3 and a self-synthesized bio cross-linker epoxidized quercetin (EQC), to develop a strong and conductive soy protein-based adhesive with mildew-proof and flame-retardant properties. A covalent cross-linked structure and noncovalent bond (hydrogen bonds and ionic bonds) were formed among SPI, EQC, DOPA, and Ag+. As well, a hybrid structure was formed via in situ polymerization of Ag NPs, resulting in an adhesive with improved water resistance. Thus, the dry and wet shear strengths of plywood bonded with resultant adhesive increased by 78% and 52.4%, respectively, relative to those of the SPI adhesive. The modified adhesive exhibited good mildew resistance (shelf life ＞ 15 d) due to the natural antibacterial properties of quercetin, and the dynamic equilibrium of Ag NPs and Ag+ in the presence of DOPA. Meanwhile, the LOI of the modified adhesive was 41.3%, which is higher than that of SPI, improving flame retardancy of the resultant plywood. Notably, the obtained adhesive exhibited conductivity owing to the presence of polypyrrole (up to 7.09 S/cm), which can be used to develop reflection-based particle board with electromagnetic shielding ability. This study provides a high-potential and feasible strategy for developing multifunctional biomass composites to replace metal and polymer materials, which is an important and practical approach to promote sustainable development of materials and reduce carbon emissions.

Fabrication and Application of Eco-friendly Bamboo Self-Bonded Composites for Furniture

Self-bonding technology is a facile and green molding approach to obtain eco-friendly and formaldehyde-free bamboo self-bonded composites (BSCs), yet the manufacture process is still immature. Here, the effects of processing parameters (moisture content of bamboo powders, hot-pressing temperature, and preset density) were comprehensively examined on the microstructure, physical properties, and mechanical properties of the BSCs for use in furniture. It was found that the optimum water resistance and mechanical properties were achieved for the BSCs made of bamboo powders of 40% moisture content. Higher temperature and preset density facilitated the formation of a more compact structure, leading to remarkable improvement in water resistance and mechanical performance. Given energy saving, the recommended processing parameters of the BSC manufacture were 40% moisture content of bamboo powders, 200 °C hot-pressing temperature, and 1.0 g/cm3 preset density, yielding high-performance BSCs with a thickness swelling of 12.8% and internal bonding strength of 0.71 MPa, which were comparable to commercial furniture-grade medium-density fiberboards. The colorful patterns could be successfully printed by a UV inkjet printer on the BSC surface and exhibited good paint film adhesion, which holds great potential for application in furniture.

Boosting the H2O resistance and NH3-SCR activity over sulfated FeCe0.5 SmaTi4Ox-S catalysts by Sm modification

In this work, a series of Sm modified sulfated FeCe0.5Ti4Ox-S catalysts were successfully prepared by a concise one-step co-precipitation method for application in flue gases denitrifications (de-NOx) generated from high sulfur content coal-fired power plants. The catalysts were carried out by XRD, Raman, N2 adsorption and desorption, TEM, EDS spectroscopy, NH3-TPD, H2-TPR, XPS, and in-situ DRIFTS characterization. Among these catalysts, FeCe0.5Sm0.3Ti4Ox-S showed the best catalytic activity, maintaining 100% NO conversion in 260–450 °C, high N2 selectivity and good resistance to water and SO2 poisoning. The results demonstrated that the addition of appropriate amount of Sm promoted the interaction between Sm, Ce, Fe and Ti, which increased the oxidation capacity and L-acid sites on the catalyst surface, improving the catalytic activity. Additionally, the increase of L acid sites also contributed to the improvement of water resistance of the catalyst. In-situ DRIFTS studies also indicated that the Sm addition promoted NH3 adsorption in the presence of water due to the reaction of special surface sulfates with H2O to form additional B acid sites, which may be the reason for the negligible effect of water on the catalytic activity. Based on various characterizations, the NH3-SCR de-NOx processes are proposed over FeCe0.5Sm0.3Ti4Ox-S in presence of H2O.

Incorporating antioxidative peptides within nanofibrous delivery vehicles: Characterization and in vitro release kinetics

L-carnosine (Car), an antioxidative dipeptide, is a promising health-promoting bioactive agent, which can be isolated from animal waste. In the present study, Car loaded pullulan (Pul)-sodium alginate (NaAlg) based nanofibrous delivery vehicles were fabricated by uniaxial, coaxial and emulsion electrospinning. The CaCl2 crosslinking was applied after electrospinning process to evaluate the effect on release behavior of Car. Results showed that Car was successfully loaded in water-in-oil-in-water (W1/O/W2) double emulsion to produce nanofibers by emulsion electrospinning. Encapsulation efficiencies were found to be 74.11% and 81.69% for the uniaxial (UENFs) and coaxial nanofibers (CENFs), respectively. Encapsulation efficiency was determined for different formulas of emulsions, whereas among the samples that could form nanofibers (NFs) and encapsulate Car, the highest value was obtained for nanofibers from emulsion-VIII (EE-VIII NFs) at 68.63%. DPPH and CUPRAC assays revealed that all electrospinning methods demonstrated protective effect on the antioxidant activity of Car and thus helped in enhancing its antioxidant potential significantly. According to in vitro digestion results, the release of Car from all electrospun NFs was predominantly controlled by Fickian diffusion mechanism. The CaCl2 crosslinking treatment improved water resistance of NFs and enhanced sustained release of Car in the gastrointestinal tract. The initial burst release of Car from EE-VIII NFs was significantly lower than for UENFs and CENFs in the gastric phase, and the release from EE-VIII NFs in the intestinal phase was followed by sustained release, with/without crosslinking treatment. It can therefore be said that the simultaneously encapsulation of Car in double emulsion and in Pul-NaAlg based electrospun NFs can provide sustained release.

Study on water resistance improvement of wood dowel rotation welding joints

Rotation welding of wood dowels has the advantages of high bonding strength, fast processing speed and green environmental protection, and is suitable for jointing nodes in furniture and wood products. However, most wood friction welding specimens have poor water resistance where the welded joints are more likely to be damaged in wet environments, which greatly limits their wider application. Previous studies focused on using natural and green materials or methods to enhance bonding strength and water resistance of friction-welded joints. This paper reveals an innovative chemical pretreatment method to improve the water resistance of rotary friction welded joints by treating the substrate blocks or dowels with reagents that successively oxidize and sulfonate the wood, and spraying the dowels with Zinc acetate alcohol solution that has a lubricant effect, followed by friction welding. The findings show that both the dry bonding strength of friction welded joints and the wet bonding strength after impregnation with cold, hot, and boiling water of dowels pretreated with oxidation and sulfonation reactions were higher than those without pretreatment and significantly superior to the traditional polyvinyl acetate (PVAc) adhesive bonding.

CuBTC Metal-Organic Framework Decorated with FeBTC Nanoparticles with Enhance Water Stability for Environmental Remediation Applications.

Metal-organic frameworks (MOFs) based on Cu-benzene tricarboxylate (CuBTC) are widely used for gas storage and removal applications. However, they readily lose their crystal structures under humid conditions, limiting their practical applications. This structural decomposition reduces the specific surface area, gas adsorption capability, and recyclability of CuBTC considerably. In this study, a stable MOF against water exposure was designed based on FeBTC nanoparticle-covered CuBTC (FeCuBTC). A simple one-pot solvothermal process that enables the epitaxial growth of FeBTC on the CuBTC surface was proposed. Structural and morphological analyses after water exposure revealed that the water stability of FeCuBTC was better than that of CuBTC, which completely lost its crystallinity. This observed improvement in the water stability of the synthesized MOF proved to be beneficial for the adsorption of formaldehyde under humid conditions. The proposed strategy herein is simple yet highly effective in the design of hetero-bimetallic MOFs with considerably improved water resistance and extended applicability for environmental remediation processes.

X-aggregation-induced emission in newly fabricated Pullulan/3-Hydroxyflavone derivative composite electrospun nanofiber mat for optical applications

A fascinating optically important 3-Hydroxyflavone derivative 2-(2,5-dimethoxyphenyl)-3‑hydroxy-4H-chromen-4-one was synthesized and its single-crystal structure was studied. This compound was used as a dopant and incorporated into the pullulan matrix by electrospinning technique. Functionalized pullulan nanofiber mat was found to possess dopant molecules organized in an X-aggregated fashion accounting for the twisted structure of the dopant molecules. The diameter of the nanofiber mat was reduced from 250 nm to 120 nm upon fabrication with dopant due to the nanofiber mat's increased crystallinity. Dopant molecules imparted absorption and emission properties into the fabricated nanofiber mat and turned it to be highly fluorescent triggering yellowish-green emission with a large Stokes shift of 193 nm due to X-aggregation. The improved water resistance of the fabricated pullulan nanofiber mat was witnessed by an increased water contact angle from 27.3° to 62.5° due to the incorporation of hydrophobic dopant molecules. The thermal and mechanical stability of the fabricated nanofiber mat was improved upon fabrication. The predicted absolute quantum yield was obtained in the 34.1- 40.3% range. The optimum indirect optical band gap of 2.25–2.50 eV and refractive index of 2.1–3.4 for the designed nanofiber mat suggested the potential application as OLED material.

A porous GO/PI coating prepared via breath figure method: Low dielectric constant with improved mechanical and water resistance properties

It is important to reduce dielectric constant while maintaining or improving water resistance and mechanical properties for the practical use of porous low-dielectric materials. Herein, a composite film in which GO and fluorinated PI (FPI) contained porous structure located on the surface of flat PI film was prepared by the simple breath figure method. The incorporation of GO/surfactant can break the design contradiction between low dielectric constant and high mechanical strength for porous structure, thereby realizing the synchronous promotion of dielectric and mechanical properties. Moreover, the water absorption of composite film was decreased significantly due to the synergy of fluorine atoms, porous structure and GO/surfactant, guarantee its high robustness to humid stress. The dielectric, water resistance and mechanical properties of the composite film could be regulated through varying the casting humidity and GO/surfactant content. A low dielectric constant of 2.3, water absorption of 0.6 % and high tensile strength of 122 MPa, with 31.11 % and 75.88 % of decrease and 26.99 % of increase compared to flat PI film was exhibited with the GO/surfactant loading of only 0.5 wt%. The dielectric constant of composite film is still below 2.5 after moisture treatment. These excellent properties facilitate the application of GO/PI composite film in microelectronics.

Effect of organically modified titania and zirconia nanoparticles on characteristics, properties of coating based on acrylic emulsion polymer for outdoor applications

AbstractEffect of titania nanoparticles modified with 3 wt% [3‐(methacrylloxy)propyl]trimethoxysilane (m‐TiO2 NPs) and zirconia nanoparticles modified with 3 wt% (3‐glycidyloxypropyl)triethoxysilane (m‐ZrO2 NPs) on properties and morphology of acrylic emulsion polymer coating was investigated. With suitable weight ratio of m‐TiO2/m‐ZrO2 NPs, the acrylic coating could be improved abrasion resistance, weather durability, reflectance index (400–1400 nm) as well as thermal‐oxidation stability in comparison with the coatings having the same content of single modified nanoparticles. The starting thermal degradation temperature of acrylic coating filled by mixture of m‐TiO2 NPs and m‐ZrO2 NPs was approximately 10°C higher than that of the acrylic coating contained separately modified nanoparticles. The mixture of m‐TiO2 NPs and m‐ZrO2 NPs were used in solar reflective paint. Replacement of rutile TiO2 microparticles by 1 wt% mixture of modified nanoparticles, the solar reflective paint (SRP) could be improved water resistance and cooling performance. The water permeability of the SRP coating with mixture of modified nanoparticles was reduced by nearly 50%. The results of cooling performance test indicated that SRP loaded 1 wt% (m‐TiO2 NPs and m‐ZrO2 NPs) (weight ratio of 1/1) replaced 1 wt% TiO2 microparticles could reduce outside temperature of chamber test by nearly 11°C and ambient inside temperature of chamber test by 7.5°C. This novel solar reflective paint is considered as promising material for outdoor applications.

Assessment of chitosan/pectin-rich vegetable waste composites for the active packaging of dry foods

In line with the growing demand for green alternatives to conventional petroleum-derived plastic packaging, fully bio-based and biodegradable biocomposites were developed for this work, for the purpose of packaging dry foods, following the principles of circular economy. Solutions of plasticized chitosan (pCS) were blended with varying amounts of hydrolyzed orange peel (hOP) waste to produce films by casting. The hydrolytic pretreatment of orange peels enabled the creation of biocomposites containing up to 80 wt% hOP, while the formulation with 70 wt% hOP had the best general performance. Chemical characterization of the developed films revealed that chitosan molecules interact electrostatically with pectin molecules in hOP. The strong interaction between chitosan and pectin molecules results in improved mechanical, barrier, and thermal properties of the composite materials compared to their individual components. In addition, the biocomposites exhibit improved water resistance due to their reduced water solubility compared to chitosan and hOP films. The migration of the films’ components in the food simulant Tenax was evaluated, and the results revealed low values, compliant with the current EU regulation. However, due to the electrostatic interactions, the films lost the antimicrobial activity of the individual components, chitosan and hOP, against E. coli and S. aureus bacteria, a property that could turn the developed films into active packaging. Finally, the optical and antioxidant properties and the biodegradability in soil of the developed films were also assayed, showing high transparency, antioxidant capacity, and fast biodegradability, reaching 62.9% weight loss after 26 days of the experiment.

Mechanical Properties and Water Resistance of Magnesium Oxychloride Cement–Solidified Residual Sludge

As a solid waste, the amount of residual sludge produced by the municipal wastewater treatment process is escalating. How to dispose it properly is attracting much attention in society. Herein, solidifying residual sludge using magnesium oxychloride cement (MOC) is promising for converting it into building materials. Various factors of mass ratio (RW/S) of liquid to solid, molar ratio (Rn) of MgO to MgCl2 in MOC, mass ratio (Rm) of residual sludge to MOC, the mass concentration of Na2SiO3 (DNa2SiO3), and dosage of fly ash (DF) influenced the unconfined compression strength (RC) of the as–obtained MOC–solidified residual sludge, and it was characterized using SEM and XRD analysis. The results show that the value of RC for MOC–residual sludge solidified blocks increased initially and then decreased as Rn and Rm increased, respectively, for 60–day curing. At 10–day curing, equilibrium RC was reached at all RW/S values except 1.38, and at 60–day curing, RC decreased with RW/S increasing. The maximum RC of 60 days of 20.90 MPa was obtained at RW/S = 0.90, Rn = 5.0, and Rm = 1.00. Furthermore, adding Na2SiO3 or fly ash in the solidifying process could improve RC. The water resistance test showed that SM13 and NF5 samples exhibited good alkaline resistance after immersion for 7 and 14 days in an aqueous solution with pH = 7.0–11.0. The water resistance of MOC–residual sludge solidified blocks decreased with increase in immersion duration in aqueous solutions. The fly ash could also help improve water resistance of MOC–solidified residual sludge in neutral and basic aqueous solutions. This work provides an important theoretical basis and possibility for the efficient disposal and comprehensive utilization of residual sludge through solidification/stabilization technology using MOC from the perspective of mechanics and water resistance.

Investigation on the potassium magnesium phosphate cement modified by pretreated red mud: Basic properties, water resistance and hydration heat

Potassium magnesium phosphate cement (MKPC) was modified by red mud pretreated with potassium dihydrogen phosphate (KH2PO4) to improve water resistance, volume stability, and economy. The effects of pretreated red mud on the fluidity, setting time, mechanical properties, water resistance, and hydration heat of MKPC were investigated. The influence mechanism of pretreated red mud on the macro performance of MKPC was clarified by analyzing composition and morphology of the hydrated products, and the hydration thermodynamics. The results showed that with the increase of pretreated red mud content, the water resistance of MKPC was significantly improved, and the peak temperature and hydration heat were significantly reduced. This is because the participation of pretreated red mud refines the crystal structure of MgKPO4·6H2O, and reduces the concentration of dead burned magnesium oxide (MgO) and KH2PO4 in MKPC mixture through filling and dilution effects. In addition, the combined action of KH2PO4 and sodium dihydrogen phosphate rich in pretreated red mud reduced the hydration heat of MKPC. When the content of pretreated red mud is 20 w%, the compressive strength of MKPC cured in water was close to that of the control group, the strength retention rate reached 0.86, and the peak temperature and cumulative hydration heat were significantly reduced, indicating that it is more suitable for emergency repair of hydraulic structures.

The influence of water absorption on reinforced polymers (FRP) using MWCNT and HGB

In the current paper, different MWCNTs filler amounts, containing PA6 and HGBs were prepared by injection moulded. The water uptake at saturation, normalized to the polyamide mass, decreases; hence the diffusion rate in both MWCNTs is slower, respectively HGBs which is faster. Injected moulded polymer samples can take less (6%) water uptake than neat polymer granules (11%). The addition of 15 wt% of multi-walled carbon nanotubes (sample 3) led to a minimum water absorption rate of 5%; this value is 15% less than the majority of the polymer composite mixtures and 1% less than pure PA6, mainly because other polymer composites which contained the HGB filler, absorbed more water. The best results highlight the improved water resistance of polyamide composite (sample 3), which reduces the impact of water on the component and expresses better applicability in the water environment than other polymer composites or even pure PA6.

Fabrication and characterization of waste fish scale-derived gelatin/sodium alginate/carvacrol loaded ZIF-8 nanoparticles composite films with sustained antibacterial activity for active food packaging

An environmental-friendly composite films containing waste fish scale-derived gelatin (FSG), sodium alginate (SA) and carvacrol loaded ZIF-8 (CV@ZIF-8) nanoparticles were designed and fabricated to develop active food packaging materials capable of sustained antibacterial activity. The microstructure and physicochemical properties of the FSG/SA/CV@ZIF-8 composite films were investigated. The incorporation of CV@ZIF-8 into FSG/SA matrix significantly enhanced the UV-light blocking and the elongation at break, improved water resistance and reduced water vapor permeability, and improved the thermal stability of composite film. The FSG/SA/CV@ZIF-8 film not only exhibited strong antioxidant activity with DPPH radical scavenging rate of 92.35 %, but also showed the satisfactory and long-acting antibacterial ability against E. coli and S. aureus due to slow release of CV from composite film. Strawberry preservation experiment revealed that FSG/SA/CV@ZIF-8 film decelerated the texture deterioration and retarded the growth of spoilage microorganism, resulting in the prolonged shelf-life of 8 days under ambient condition, indicating its promising application prospect in food preservation packaging.

Hardening and microstructural properties of red mud modified magnesium ammonium phosphate cements

Magnesium ammonium phosphate cement (MAPC) was modified by red mud pretreated with ammonium dihydrogen phosphate (NH4H2PO4) to improve water resistance, volume stability, and economy. The effects of pretreated red mud on fluidity, setting time, mechanical properties, and water resistance of MAPC were investigated. Combined with the composition and morphology of the hydration products, the mechanism of the influence of pretreated red mud on macroscopic properties was clarified. Furthermore, the analysis of hydration temperature, hydration heat, and the thermodynamics of the hydration reaction was to expound the effect of the pretreated red mud and the rich sodium phosphate salt on the hydration hardening process of MAPC. The experimental results showed that the water resistance of MAPC was obviously improved, and hydration peak temperature and hydration heat were significantly reduced with the increase of pretreated red mud content. When the pretreated red mud was blended at 30%, the mechanical properties of MAPC were slightly reduced, the water resistance was increased by 97.4%, and the peak hydration temperature and total heat were reduced by 27.8% and 28.4%, respectively, compared with the control group. This is due to the filling and diluting effects of red mud particles, especially the dilution of dead-burned magnesium oxide (MgO) and NH4H2PO4 concentration in the MAPC mixture. In addition, it was attributed to the compounding effect of sodium dihydrogen phosphate, which was abundant in the pretreated red mud.

Improving water resistance and mechanical properties of waterborne acrylic resin modified by octafluoropentyl methacrylate

Improving water resistance and mechanical properties of waterborne acrylic resin modified by octafluoropentyl methacrylate