Alkali-activation of marble sludge: Influence of curing conditions and waste glass addition

The use of marble sludge as precursor for new alkali activated materials was assessed studying three different curing conditions (air, humid and water immersion, respectively), after an initial curing at 60 °C for 24 h, and two glass powder fractions additions (2.5 and 5.0 vol%). Microstructural, physical (drying shrinkage, Fourier transform-infrared (FT-IR) spectroscopy, X-ray spectroscopy (XPS)), thermal (differential thermal analysis – thermogravimetric analysis, DTA-TGA) and mechanical (flexural and compressive strength) properties were investigated. Air curing was the most favourable atmosphere for mechanical properties development because it promotes Si-O-Si polymerization and gel densification, as demonstrated by FT-IR and FE-SEM observations, respectively. Satisfactory mechanical properties were achieved (18 MPa and 45 MPa, for flexural and compressive strength, respectively) in particular for glass containing mixtures. Moreover, glass powder addition significantly reduced drying shrinkage of air-cured samples because it operated as a rigid aggregate in the matrix and strengthened the formed gel.     

Effect of calcium carbonate on the preparation of glass ceramic foams from water-quenched titanium-bearing blast furnace slag and waste glass

ABSTRACT

Glass ceramic foams were fabricated with powder sintering technology at a low temperature (900°C), using water-quenched titanium-bearing blast furnace slag (WTS) and waste glass as the primary raw materials. Additionally, calcium carbonate, sodium borate and sodium phosphate were chosen as sintering aids to form excellent performance products. The effects of calcium carbonate additions on foaming process, crystal content, morphology and properties of the prepared samples were systematically researched. The research indicates that increasing the calcium carbonate content made the foaming process harder and the pore size got more uniform. Consequently, the compressive strength and bulk density increased, while the porosity and water absorption decreased. The homogenous porous structures and optimal comprehensive properties were achieved with 5–7?wt-% CaCO₃ addition, including a bulk density of 0.79–0.82?g?cm^–3, porosity of 73.13–75.28%, water absorption of 3.29–3.75% and compressive strength of 13.13–13.85?MPa.     

Effect of curing temperature on properties and solvent welding strength of ovalbumin

Effect of curing temperature on properties of ovalbumin has been investigated. Functional basis, crosslinking degree, tensile strength, and hardness increases with rising curing temperature. The increase of visible transmittance and the decrease of absorption accompany with increasing wavelength. The absorptive peak shows at 440–450 nm and the wavelength of the absorptive peak increases with the rising curing temperature. The relationship of joint strength with solvent welded joints of ovalbumin to their microstructure is also investigated. Ovalbumin can promote joint strength after the treatment of distilled water and curing. Comparing joint strength with fracture morphology, the smoother fracture surface morphology is related to the maximum tensile and shear joint strength, respectively. The joint strength is increasing with curing temperature and compressive stress, and the joint strength of treatment with 150°C curing temperature and 0.12 kgf/mm² compressive stresses are larger than its original tensile fracture strength of cured ovalbumin at same curing temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Gel Composition and Strength Properties of Alkali‐Activated Oyster Shell‐Volcanic Ash: Effect of Synthesis Conditions

The gel composition and mechanical properties of alkali‐activated oyster shell‐volcanic ash were investigated at different NaOH concentrations (8, 12, and 15M) and curing temperatures (60°C and 80°C) in wet and dry conditions. XRD, FTIR, SEM‐EDS, and TGA‐DSC were used for microstructural characterization of the binder. The gel composition of the system was found to be influenced by NaOH concentration and was not affected when curing temperature was varied from 60°C to 80°C. The main phase was N,C–A–S–H for all alkali‐activated oyster shell‐volcanic ash, with C–S–H as secondary phase for some samples and contains high percentage of iron. The splitting at υ₃ = 1400–1494 cm^?1 on FTIR spectra corresponded to the elimination of the degeneracy due to the distortion of CO₃^2? group. The high degree of splitting indicated that this carbonate group is linked to Ca²⁺. The compressive strength was influenced by curing temperature and the formation of a secondary phase. The compressive strength in dry condition increased roughly between 28 and 180 d for some samples, while in wet condition, the partial dissolution of Si–O–Si bonds of some silicate phases resulted in a reduction of strength.     

Mechanism of crosslinking Tencel woven fabric for superior easy‐care properties and analysis using fluorescence microscopy

A crosslinking treatment to impart easy‐care properties to Tencel fabric has been investigated, using dimethyloldihydroxyethylene urea (Reaktant DH) as crosslinking agent and magnesium chloride hexahydrate as catalyst. Nonconventional treatment techniques such as “flash curing,” “moist curing,” “pad‐batch‐cure,” and “pad‐dry‐dry steam cure” are used to facilitate better penetration of crosslinking monomer into the fiber interior. Easy‐care properties of Tencel fabrics using these techniques are evaluated and compared with those treated with resin monomer using conventional pad‐dry‐cure process. Analysis of treated fabric using a fluorescent labeling technique and image analysis shows that nonconventional techniques significantly improve the penetration of crosslinking agent. The results further suggest that these techniques can be used to improve abrasion resistance and fabric handle of Tencel woven fabric. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2154–2161, 2006     

Toughening mechanism of rubber reinforced epoxy composites by thermal and microwave curing

The carboxyl terminated polybutadiene (CTBN) is utilized to improve the toughness of diglycidylether of bisphenol A epoxy cured by heat and microwave. The change of viscosity, chemical groups, and the glass transition temperature (T_g) of system are analyzed. The impact performance is characterized to evaluate the fracture toughness, and tensile properties also are investigated. The fracture morphologies are observed by the scanning electron microscopy for exploring toughening mechanism. The viscosity results indicate that viscosity of system increases with increasing of CTBN, demonstrating the formation of precrosslinking and interpenetrating network structure of two phases. The Fourier transform infrared spectrometer results show that effective chemical bonds are formed between CTBN and epoxy resins. The T_g decreases with introducing CTBN, indicating the decline of crosslinking density, which further suggests inherent three‐dimensional structure have been changed. The impact strength and energy increase with increasing of CTBN, and reach a maximum value of 5.92 kJ/m² and 0.13 kJ at 15% for thermal curing, respectively, increased by 36.8% and 23.1% relative to microwave curing system, while tensile strength and modulus reach the optimum at 5%. Scanning electron microscopy observation finds that “plastic tensile” and “microvoid” deriving from “sea‐island” structure exist, presenting the ductile fracture features. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45767.     

Effect of cure history on dynamic mechanical properties of an epoxy resin

The effect of cure history on the dynamic thermomechanical properties of a high temperature curing epoxy resin has been studied using torsional braid analysis. In isothermal cures “full cure” is not possible except at temperatures above the maximum glass transition temperature (T_g) of the cured resin, hence the necessity of a “post-cure” after lower temperature isothermal cures. The highest T_g and maximum cross-linking in the cured resin was for a linear heating rate of 0.05°C/min from 30 to 200°C; higher heating rates lead to lower glass transition temperatures.     

Thermal stability and deformation of poly(acrylic acid)–metal oxides

In this work, we investigated the thermal stability and deformation of the compound of poly(acrylic acid) (PAA) and metal oxides (ZnO, CaO, CuO, Al₂O₃, and Cr₂O₃). The kinetic parameters of the desorption of water from PAA–metal oxide were calculated. The activation energies of the water desorption of PAA–metal oxide were less than 5 kcal/mol. The order of bonding capability of oxygen (PAA–O–metal) and water was PAA–CaO > PAA–ZnO > PAA–CuO > PAA–Cr₂O ₃ > PAA–Al₂O₃. The reaction types of the composites were clarified. Incorporating metal oxide into PAA increased the thermal stability. The factors which influence the mechanical properties of the composites, e.g., the chemical compositions, curing environment, and curing time, were also studied. The various curing environments (pure water, 0.1N HCl, 0.1N NaOH, and methanol) decreased the compressive strength of PAA—metal oxide. Moreover, the thermal stability and compressive strength of PAA–ZnO and PAA–CuO reached an optimum because of their crosslinking nature. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2021–2027, 1997     

Effect of the length and the volume fraction of wavy steel fibers on the behavior of self-compacting concrete

Self-compacting concrete (SCC) is a highly workable concrete that fills formwork under its own weight (without any vibration or impact). It also passes easily through small spaces between reinforcement bars. The inclusion of fibers in such concrete limits the concrete shrinkage cracks at early age and enhances some of its properties. However, fibers may affect the flow characteristics of SCC. In this paper, three wavy steel fibers (SF) of different lengths, 35, 40, and 50 ± 2 mm with six different volume fractions (V_f) of 0.3, 0.5, 0.8, 1, 1.2, and 1.4% were used in SCC. The experimental results showed that the addition of SF with higher V_f content and longer length decreases the workability of SCC, reduces its passing ability and increases the possibility of blockage. Mechanical performances of concrete in terms of flexural strength and elasticity modulus were improved, where the slightly compressive strength decreased with an increase in V_f content of SF.     

Bone ash reinforced geopolymer composites

Potassium-based, geopolymer composites were made with BASF^® metakaolin and Mymensingh clay-derived metakaolin from Bangladesh. Since the natural Mymensingh clay contained 40 wt.% quartz, this same amount of quartz particulates was added to the BASF^® metakaolin to make a synthetic analog of the natural calcined clay. By analogy with bone china, bone ash or calcined hydroxyapatite (5CaO•3P₂O₅ or “HA”) particles, having a Ca: P ratio of 3.3:1, were added to make the three types of geopolymer-based composites described above. For less refractory particulate additions, dicalcium phosphate (DCP) (2CaO•P₂O₅ or “DCP”) particles, having a Ca: P ratio of 2:1, were also added to another set of geopolymers. The ambient temperature compressive and flexural strengths were measured for all of the geopolymer composites. The HA or DCP reinforced geopolymer composites were fabricated and heat-treated to 1150°C/1 h, after which they were converted to their mineralogical analogs. Their mechanical properties of compressive and 3-point flexural strengths were again measured. Flexural strengths of 22.42 ± 11.0 MPa and 31.97 ± 8.3 MPa were measured in 1 × 1 × 10 cm³ heat-treated geopolymer bars reinforced with 10 wt.% of DCP and in geopolymer reinforced with 10 wt.% DCP +40 wt.% quartz additions, respectively. Significant improvements to ambient temperature properties were observed due to the self-healing effect of the flowing amorphous DCP, whose presence was verified by SEM. The geopolymer samples exhibited reduced water absorption (WA) (on a percentage dry weight basis) of within 0.03-0.5% after being heated at 1100℃/1 h and 1125℃/1 h, as compared with those at room temperature, which varied between 2.56% and 7.89%.     

Curing kinetics and curing process of phenolic impregnated carbon ablator

Phenolic impregnated carbon ablator (PICA), which is composed of the phenolic resin (PR) and carbon fiber, is of particular interest to researchers in the aerospace field. In this work, PICA was prepared by the double‐stage isothermal heating curing. Then, the curing kinetics of boron‐modified phenolic resin (BPR) was investigated by non‐isothermal differential scanning calorimetry method in order to optimize the curing temperature of BPR. Further, the effect of the heating rate during curing process on the compressive strength of PICA was discussed in detail. The experimental data show that the curing of BPR needs more energy so that the curing temperature of BPR under different condition is higher than that of virgin PR. Notably, with the increasing heating rate during the curing process, the micro‐cracks increase and the compressive strength of PICA decreases. Once the heating rate exceeds a critical value, the micro‐cracks no longer increase and the heating rate has insignificant effect on the compressive strength. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45434.     

Preparation and characterization of epoxy/slag composite for cement slurry applications

In this study, epoxy/slag composites (ESCs) were prepared by using diglycidyl ether of bisphenol‐A epoxy resin, water‐quenched granulated blast furnace slag as filler, phenolic aldehyde amine as hardener, and titanate as coupling agent. The properties of ESC, including chemical structure, thermal stability, wetting properties, and morphological structure, were investigated by using Fourier transform infrared spectroscopy, thermogravimetric analysis, a contact angle meter, scanning electron microscopy, and energy dispersive spectrometry. The results show that ESCs possess excellent thermal stability, hydrophilicity, and good compatibility with cement slurry compared to pure epoxy. In addition, the applications of ESC in a cement slurry were also investigated. It was found that the fluidity, free water, fluid loss, and content of Ca(OH)₂ decreased, while the compressive strength increased with the incorporation of slag into the epoxy matrix. These features were attributed to the pozzolanic reaction of slag by consumption of Ca(OH)₂ to form calcium silicate hydrate (C‐S‐H) gel which contributed more to the compressive strength of set cement. Finally, lightweight cement containing ESCs exhibited high strength without affecting the density of the light cement slurry under curing pressure and at high mixing rate compared with lightweight cement made of floating beads. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43359.     

Resorcinol in high solid phenol−formaldehyde resins for foams production

The acid curing agent content and foaming temperature could be reduced by improving the resol reactivity. In this study, highly active and solid phenol?resorcinol?formaldehyde copolymer resins (PRFRs) with different resorcinol/phenol (R /P ) molar ratios and formaldehyde/(phenol + resorcinol) [F /(P + R )] molar ratios were synthesized through the copolymerization of resorcinol, formaldehyde, and phenol. Phenol?resorcinol?formaldehyde foams (PRFFs) were prepared with synthetic PRFRs. The results showed that PRFR‐2 exhibited higher reactivity, faster curing speed, and better thermal stability. In addition, the foam produced with the PRFR‐2 had improved mechanical and flame retardation properties and a compressive strength of 0.18 MPa, a flexural strength of 0.25 MPa, and a limited oxygen index (LOI) greater than 37%. The increased reactivity of the PRFRs correlated with the changing mechanical properties of PRFFs because of the effects of resorcinol and the molar ratio of formaldehyde to phenol and resorcinol. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44881.     

Effects of TMPTMA and silane on the compressive strength of low‐temperature cured acrylic polymer concrete

This study addresses the effects of additives on the compressive strength of low‐temperature cured acrylic polymer concrete (PC). Three curing temperatures (0°C, ?10°C, and ?20°C) and five ages (6, 12, 24, 72, and 168 h) with two different types of additives [trimethylolpropane trimethacrylate (TMPTMA) and silane] were investigated. As a result, the compressive strength tended to decrease as the curing temperature decreased. The compressive strengths at 24 h were approximately 90% of those at 168 h at both curing temperatures of 0°C and ?20°C, indicating that the rate of early age strength development was quite high even at a very low curing temperature range. The results of two‐way variance analysis revealed that silane had a greater impact on the compressive strength than TMPTMA. About 13%–23% strength improvements with a 168‐h compressive strength of over 80 MPa could be obtained at ?20°C by adding silane. Furthermore, this study proposed optimum mixture proportions of acrylic PC that generate a working life of 50–70 minutes with a compressive strength of 80 MPa at subzero temperatures. The findings of this study are expected to be effectively used in field applications of acrylic PC, especially in the cold regions during winter season. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40939.     

The effects of curing cycles on properties of the epoxy system 3221/RH glass fabric composites

In this work, the epoxy system 3221 and its glass fabric laminates were thermally cured under different curing temperatures. The curing degree of the resin was increased with elevated reaction temperature. Dynamic mechanical analysis was performed on the laminate coupons and glass transition temperature (T_g) and relative stiffness (E′) of composites were measured before and after soaked in distilled water at 70°C. A shift in glass transition temperature to higher values and the splitting of the tan δ curve were observed with extent of cure under dry conditions. T_g values shifted to lower temperatures after immersion. Under wet condition, the change in T_g1 was very small when the curing degree was up to 96%. The relative stiffness experienced a reduction both in initial modulus and the initial sharp drop temperature after immersion. It also suggested that the excessively high curing temperature (>130°C) had a negative effect on the retention of relative stiffness under wet condition. Both the interlaminar shear strength and dielectric properties of laminates were determined before and after immersion. The compared results demonstrated that the elevated curing temperature played a good influence on both of the properties before aged. However, for samples cured above 130°C, lower retention of interlaminar shear strength and poor dielectric properties were observed during immersion due to their higher moisture contents. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Preparation and properties of rigid polyimide foams derived from dianhydride and isocyanate

A series of rigid polyimide (PI) foams were synthesized via the reaction of a first solution with a second solution. The first solution was isocyanate‐terminated polyimide prepolymers; the second solution contained deionized water and surfactant. The effect of different water contents and isocyanate index on the structures and properties of rigid PI foams were investigated. The apparent density, hardness, compressive strength, and the 5% weight loss temperatures (T_5%) decreased with the increase of water content. With the increase of isocyanate index, the apparent density and the T_5% values decreased, whereas the glass transition temperatures (T_g) increased and the hardness, compressive strength first increased and then decreased. The rigid PI foams composed of closed‐cells were confirmed by scanning electron microscopy. The maximum compressive strength of rigid PI foams prepared was up to 1.31 MPa. Moreover, excellent thermal stability was presented with the T_5% values were all above 360°C and the residual weights of the foams (R_w) were more than 50% at 800°C. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Purification of Polluted Source Water with Ozonoation and Biological Activated Carbon

In order to determine effective processes for purifying polluted source waters 1n Harbin City, various processes consisting of ozonation, sand filtration, and/or GAC filtration and adsorption, i.e., ozonation ( “O₃” Process), ozonatlon/sand filtration ( “O₃ + SF” Process), ozonation/biological activated carbon ( “O₃ + BAC” Process), ozonation/sand filtration/biological activated carbon ( “O₃ + SF + BAC” Process), and granular activated carbon (“GAC” Process) were tested In an 8 m³/d capacity pilot plant. In addition, a small plant of 500 L/d capacity was used to conduct comparative studies between the two processes “GAC” and “O₃ + BAC”, as well as two types of carbon.     

Study of SiC fiber axial compressive behavior using tensile recoil measurement

SiC fibers have been widely investigated as reinforcements for advanced ceramic matrix composites owing to their excellent high-temperature properties. However, the axial compressive strength of SiC fibers has not been thoroughly studied. In this study, the compressive behavior of two SiC fiber types containing different compositions and thermal degradation were characterized by tensile recoil measurements. Results illustrated that the SiC fiber compressive strength was 30%–50% of its tensile strength, after heat treatment at 1200℃–1800℃ for 0.5 h in argon. The fiber compressive failure mechanism was studied, and a “shear-bending-cleavage” model was proposed for the recoil compression fracture of pristine SiC fibers. The average compressive and tensile strengths of the pristine SiC-II fiber were 1.37 and 3.08 GPa, respectively. After treatment at 1800℃ for 0.5 h in argon, the SiC-II fiber compressive strength decreased to 0.42 GPa, whereas the tensile strength reduced to 1.47 GPa. The mechanical properties of the fibers degraded after high-temperature treatment. This could be attributed to SiC grain coarsening and SiC_xO_y phase decomposition.     

Improving the water resistance and adhesion strength of a mixed alkali silicate adhesive by optimizing the molar ratio and curing conditions

Abstract

It is important to eliminate the use of organic adhesives that are harmful to humans and cause environmental pollution. Environmentally friendly, harmless inorganic adhesives are being actively studied. Here, we found that optimized curing was possible when the curing time was controlled via temperature adjustment. We first prepared basic alkali silicate solutions, containing sodium, potassium, and lithium silicate, and compromised them in terms of water resistance. Adhesive strength was measured according to ASTM D3165 using a universal testing machine. The target material, a stainless steel (SUS) specimen, was prepared as described by ASTM D3165. Moreover, to develop fast thermal curing, the effects of two parameters were investigated: curing time and temperature. The temperature range tested was 80–140?°C for 2–36?h; we assessed adhesive strength. The maximum shear strength was obtained after thermal curing at 80?°C for 36?h, 120?°C for 12?h, and 140?°C for 2?h. However, when thermal curing proceeded past the maximum shear strength, the shear strength decreased, attributable to a reduction in the adherent area.     

Post curing effect of poly epoxy on visco‐elastic and mechanical properties of different sandwich structures

Poly epoxy is a high performance room temperature cured epoxy system which provides excellent physical and mechanical properties. However, the effects of post curing of this resin system on the properties of different sandwich structures are unknown. This study aims to evaluate the effect of post curing (at 70°C for 2 hr) on the edgewise compressive and flexural strengths of a sandwich structure, constructed with Styrofoam and honeycomb as core materials and a plain weave carbon fabric as face sheet. Tested factors evaluated from edgewise compressive tests were as follows: peak load, compressive strength, and crash energy absorption of sandwich structures while core shear stress and bending stress of sandwich structures were determined and compared with flexural tests. It was observed that post curing affects significantly on the bending and compressive strengths of the sandwich structures. However, the data obtained for crash energy absorption suggested that the effect of post curing on the core shear strength and the total deflection was statistically insignificant. The matrix polymer was also inspected using dynamic‐mechanical thermal analysis to assess the changes in glass transition temperature and degree of conversion due to post cure. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers