Calcium Sulfate Whiskers Research Articles

Heterogeneous nucleation of calcium sulfate whisker in polyamide 6 and its efficient reinforcement on tribology performance

AbstractFor traditional materials, a polymer composite with high performance and large‐scale production is still the goal pursued by researchers. In our work, polyamide 6/calcium sulfate whiskers (PA6/SCW) composites were fabricated via melt‐compouding method. The calcium sulfate whisker based on gypsum mineral was used as reinforcement. After grafting silane coupling agent on the whisker surface, the whiskers showed a significant reinforcing effect in polyamide. The mechanics and tribology performance of the samples had been significantly inhanced. Based on the nucleation mechanism of lattice matching, calcium sulfate whiskers have obvious heterogeneous nucleation effect in PA6 matrix, while the crystallization period was slightly prolonged. This was caused by the network structure formed by the whiskers in the matrix, which impeded the free movement of polymer chain segments. In combination with the orientation degree of the molecular chains measured by the interdigital electrode, the reinforcing effect of the oriented PA6 specimens was derived from the orientation arrangement of the whiskers and the efficient load transfer.Highlights Mechanical and tribological properties of composite were significantly improved. The composite could achieved large‐scale production due to simple preparation. The whiskers had obvious heterogeneous nucleation effect in matrix. The reinforcing effect was derived from efficient load transfer from whiskers.

Study on design optimization, road performance verification and preparation process selection of hybrid fiber reinforced asphalt mixture composite

To achieve long-lasting, high-strength, and sustainable asphalt pavement, this study prepared a hybrid fiber asphalt mixture using micron-scale calcium sulfate whiskers (CSW) and millimeter-scale basalt fibers (BF). The response surface method was employed to optimize the mix design, develop a prediction model, and verify road performance. The preparation process was refined based on the optimal mix design. The findings revealed that the best overall road performance was obtained with 5 % CSW content, 6 mm BF length, and 0.32 % BF content. The mixture demonstrated optimal performance with CSW wet mixing and BF dry mixing. Additionally, testing the fiber asphalt mixture at the mixture level was found to be crucial, as results can vary from those obtained at the mastic level. This study provides an in-depth analysis of the hybrid fiber asphalt mixture’s action mechanisms in material optimization, performance verification, and preparation processes, offering valuable insights for related research and engineering applications of hybrid fibers.

On the enhanced properties of composite asphalt via adding surface modified calcium sulfate whisker-SBR

With the aim of improving the durability and safety, erosion time, and cost-effective of asphalt road, a composite of modified calcium sulfate whisker-styrene butadiene rubber modified asphalt (MCSW-SBRMA) was prepared via thermal doping. Firstly, stearic acid and titanate coupling agent (NDZ-201) were used as a modifier to transform calcium sulfate whisker (CSW) into MCSW via wet modification method at 60 °C and anhydrous ethanol as a dispersant. What is more, the optimum loading of modifier (a mixture of 25% stearic acid + 75% NDZ-201) was found to be at 2% to prepare MCSW. Subsequently, a composite of MCSW-SBRMA was prepared with different loading of MCSW (i.e. 2% to 8%) to enhance the softening point of asphalt. In this study, it was found that 4% of modifiers was the best composition to improve the MCSW-SBRMA properties as elucidated in the orthogonal experiment table L16(42). The effects of MCSW and SBR addition on several properties of asphalt were studied by multiple routine tests including penetration, segregation test, and so on. The results show that: 2% to 8% MCSW can increase the softening point of SBR modified asphalt (SBRMA) by 7% to 8%. 4% MCSW increased the PG of SBRMA from 64 to 70, which greatly improved the high temperature characteristics of asphalt. The 5 °C ductility of MCSW-SBRMA is greater than 100 cm, which greatly improves the low temperature performance of asphalt. Through the application of fluorescence microscopy (FM), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and energy dispersive spectroscopy (SEM-EDS), it has been demonstrated that MCSW-SBR effectively alters asphalt in a highly uniform manner, with some MCSW still retaining large cross sections, thereby facilitating the dispersion of shear stress and enhancing the durability of asphalt.

Enhancing mechanical properties of PVC composites through surface composite modified calcium sulfate whiskers

Enhancing mechanical properties of PVC composites through surface composite modified calcium sulfate whiskers

Revealing the role of multi-scale fibers in the compressive behavior of a novel ultra-high performance concrete subjected to elevated temperatures

Ultra-high performance concrete has received widespread attention due to its excellent performance. However, the mechanical properties can seriously degrade at high temperatures. To improve the thermal resistance, cenospheres and multi-scale fibers such as polyethylene fiber, steel fiber, calcium sulfate whisker, carbon fiber, and carbon nanotubes, are added to develop a type of ultra-high performance (MSFUHPC) in this work. The effects of cenospheres and multi-scale fibers on peak strain, compressive strength, Young's modulus, specific toughness and stress-strain curve are studied at various temperatures (25 °C, 200 °C, 400 °C, 600 °C, and 800 °C) through uniaxial compression tests. Additionally, mercury intrusion porosimetry tests and scanning electron microscope tests are used to discuss the effect of cenospheres and multi-scale fibers on the microstructure. The results demonstrate that both CE and multi-scale fiber can reduce the thermal damage of MSFUHPC. The multi-scale fiber can significantly improve the mechanical strength of the material, while CE has the opposite effect. It is found that microscale and nanoscale fibers have negligible effect on the specific toughness, while the effect of CE on specific toughness depends on the temperature and its content. Results show that the incorporation of multi-scale fibers effectively decreases the fraction of large pores while simultaneously refining the pore structure and enhancing the proportion of gel pores. Furthermore, the stress-strain relationship of MSFUHPC is established by considering the influence of multi-scale fiber content and high temperature.

Synthesis of calcium sulfate whiskers via acidification exploiting FGD gypsum for improved binder properties

This research focuses on the synthesis of calcium sulfate whiskers using FGD (Flue Gas Desulfurization) gypsum as raw material through the acidification method and their utilization in gypsum binders. The acidification method using H2SO4 (1.5 mol/L) is distinguished by its sustainability and resource efficiency. The addition of Calcium Sulfate Whisker as an activator enhances the binder's properties by increasing its strength, durability, resistance to environmental factors, and overall structural integrity. The effects of different reaction parameters on the properties and microstructure of CSW have been studied. This research has the potential to bring about significant improvements in various applications, from construction materials to industrial products. Calcium Sulfate Whiskers act as pore fillers within the binder matrix which reduces the porosity and helps to decrease water absorption up to 12%. CSW is characterized by its needle-like structure, which provides an intricate network within the binder matrix. SEM images showed the strong interfacial bonding between the whiskers and the binder matrix, enhanced by the rough surface of the whiskers, which improves mechanical interlocking and adhesion. CSW demonstrates its potential as a highly active component in the binder. The whiskers facilitate efficient nucleation sites, accelerating the hydration reactions within the binder and enhancing the overall performance of the binder. CSW incorporation in the binder increases the compressive strength by up to 21.6% and flexural strength by 37%. The exceptional mechanical strength and efficient nucleation sites provided by CSW contribute to an increase in the workability of the binder and make it suitable for interior as well as exterior applications. These interconnected facets collectively position the project as a valuable and highly pertinent contribution, where sustainable innovation and improved material properties are of paramount importance. It potentially reduces the need for traditional additives with higher environmental impacts, making the binder formulation more eco-friendly.

Understanding Toughening Mechanisms and Damage Behavior in Hybrid-Fiber-Modified Mixtures Using Digital Imaging

Pavement cracking is a primary cause of early damage in asphalt pavements, and fiber-reinforcement technology is an effective method for enhancing the anti-cracking performance of pavement mixtures. However, due to the multi-scale dispersed structure of pavement mixtures, it is challenging to address cracking and damage with a single fiber type or fibers of the same scale. To investigate the toughening mechanisms and damage behavior of hybrid-fiber-modified mixtures, we analyzed the fracture process and damage behavior of these mixtures using a combination of basalt fiber and calcium sulfate whisker hybrid fiber modification, along with semicircular bending tests. Additionally, digital imaging was employed to examine the fracture interface characteristics, revealing the toughening mechanisms at play. The results demonstrated that basalt fibers effectively broaden the toughness range of the modified mixture at the same temperature, reduce mixture stiffness, increase residual load at the same displacement, and improve crack resistance in the mixture matrix. While calcium sulfate whiskers enhanced the peak load of the mixture, their high stiffness modulus was found to be detrimental to the mixture’s crack toughness. The fracture interface analysis indicated that the three-dimensionally distributed fibers form a spatial network within the mixture, restricting the relative movement of cement and aggregate, delaying crack propagation, and significantly improving the overall crack resistance of the mixture.

SO3 removal by submicron absorbents synthesized via inhibition method: The product layer grows like parallel peaks

Injecting calcium hydroxide powder into the flue gas is an effective strategy for SO3 removal. However, commercial calcium hydroxide has several disadvantages, including large particle size, low efficiency, and unsuitability for excessive grinding. In this work, sub-micron calcium hydroxide was synthesized by an inhibition method and its performance for SO3 removal from flue gas was investigated on a pilot-scale platform (120 Nm3/h). When the concentration of sodium alginate solution was 100 mg/L, the average particle size of calcium hydroxide decreased from 13.66 µm to 0.84 µm, which improved the SO3 removal (92.1 %) and conversion of the absorbent. The results of the fixed-bed experiments indicate that the absorption kinetics of the reaction is consistent with the Bangham model. In addition, density functional theory verifies that calcium hydroxide captures SO3 by chemisorption. The AFM image shows that the calcium sulfate whiskers produced during the reaction grow like parallel peaks on the adsorbent surface. The calculations suggest that the driving force for SO3 adsorption originates from Ca-p orbital (Ca(OH)2) and O-s orbital (SO3) hybridization. This study complements the island growth mechanism for gas-solid two-phase reactions and provides an effective method for removing SO3 from flue gas in coal-fired power plants. In addition, it will provide an important reference for the development of submicron adsorbents.

A Study on the Mechanical and Wear-Resistance Properties of Hybrid Fiber Mortar Composites with Low Water-Cement Ratios.

Based on mortar composites with a low water-cement ratio, the effects of hybrid aramid fiber (AF), calcium sulfate whisker (CSW), and basalt fiber (BF) on their mechanical properties and wear resistance were studied, and the correlation between wear resistance and compressive strength are discussed. A microstructure analysis was conducted through scanning electron microscopy (SEM) and the nitrogen-adsorption method (BET). The research results show that compared with the control group, the compressive strength, flexural strength, and wear resistance of the hybrid AF, CSW, and BF mortar composites with a low water-cement ratio increased by up to 33.6%, 32%, and 40.8%, respectively; there is a certain linear trend between wear resistance and compressive strength, but the discreteness is large. The microstructure analysis shows that CSW, AF, and BF mainly dissipate energy through bonding, friction, mechanical interlocking with the mortar matrix, and their own pull out and fracture, thereby enhancing and toughening the mortar. A single doping of CSW and co-doping of CSW and AF can refine the pore structure of the mortar, making the mortar structure more compact.

Effect of multiscale fibers and cenospheres on the uniaxial tensile behavior of ultra-high performance concrete subjected to high temperatures

Exposure to high temperatures causes a significant deterioration in the mechanical properties of ultra-high-performance concrete. Considering the characteristics of multiscale defects, it is expected to improve the residual tensile performance of ultra-high-performance concrete by incorporating multiscale fibers (including polyethylene fibers, steel fibers, calcium sulfate whiskers, carbon fibers, and carbon nanotubes). An investigation is conducted to examine the impact of multiscale fibers, CE, and temperature ranging from 25 to 800 °C on several aspects of multiscale fibers ultra-high-performance concrete (MSFUHPC), including first cracking strength and strain, ultimate strength and strain, failure mode, as well as the tensile stress-strain relationship. The results show that above 400 °C, multiscale fibers can enhance the first cracking strength, and the effects of calcium sulfate whiskers and CE on the first cracking strain depend on the temperature and their content. It is found that Steel fibers and CE can enhance the strain-hardening ability, and multiscale fibers and CE can increase the residual tensile strength and peak strain at high temperatures. At room temperature, multi-scale fibers and CE increase the maximum tensile strength and ultimate strain of MSFUHPC by 1.28 and 45.92 times, respectively. Moreover, multiscale fibers can refine the pore structure and reduce the porosity at 800 °C. While CE can decrease the increasing rate of porosity with temperature. Furthermore, the uniaxial tensile stress-strain relationship of MSFUHPC after being subjected to high temperatures is suggested based on experimental results, taking into account the influence of multiscale fibers, CE, and temperature.

Effect of calcium sulfate whiskers on mechanical properties and enhancement mechanism of metakaolin-based polymer mortar

Effect of calcium sulfate whiskers on mechanical properties and enhancement mechanism of metakaolin-based polymer mortar

Evaluation of rheological behavior and self-healing performance of calcium sulfate whisker-reinforced polyurethane modified asphalt

This study prepared calcium sulfate whisker (CSW) reinforced polyurethane (PU) composites and innovatively used them in asphalt modification to improve the strength and toughness of asphalt. The rheological and self-healing properties of asphalt modified by CSW-reinforced PU (CRP) were evaluated through rheological and self-healing tests. The results indicated that CRP enhanced the modified asphalt's high- and low-temperature properties and fatigue resistance. Compared with matrix asphalt, the high-temperature performance of PC22 is improved by 76.8 %; Tg,DMTA is reduced by 3.61°C; the fatigue life is increased by 2.9–4.5 times. However, excessive CSW tends to absorb more lightweight constituents, leading to a decrease in both low-temperature performance and fatigue resistance. Self-healing tests show that CSW-reinforced PU can improve the self-healing performance of asphalt by 64.7 % compared to matrix asphalt. It is believed that the bridging effect of CSW and the cross-linked network of PU play a key role together. Of the dosages tested here, the optimal dosage of CSW was 10 % by weight of PU, and the optimal dosage of CRP was 20 % by weight of asphalt. This study confirms the feasibility of CRP for asphalt modification and provides a method to achieve high-performance modified asphalt that can be used on roads in cold areas and airport pavements. In addition, CSW's partial replacement of PU can significantly reduce the cost of polyurethane modified asphalt pavement.

In‐situ polymerization modified calcium sulfate whiskers and their application in PP composites research

AbstractCalcium sulfate whiskers (CSW) exhibit significant surface polarity and high surface energy, leading to aggregation when directly incorporated into polymer matrices, significantly affecting the mechanical properties of the composites. Sodium oleate (SO) was used to modify CSW, introducing –C=C– active groups on the surface, followed by in‐situ graft polymerization of sodium oleate‐modified CSW (SO‐CSW) with methyl methacrylate (MMA) to prepare CSW‐g‐PMMA composites. The modification mechanism of SO and PMMA on CSW, as well as the surface modification effects on CSW, were studied using DRIFT, XRD, XPS and TEM. The results show that oleic acid ions adsorb onto the surface of CSW in two forms. One is chemisorption, in which the oleic acid ions are adsorbed on the calcium ions site on the surface of CSW in a bridging way. The other is physical adsorption, oleic acid ions and dissolved calcium ions in the form of precipitation adsorbed on the outermost layer of CSW. After in‐situ polymerization, PMMA was successfully grafted onto the surface of CSW, and the thickness of the surface PMMA coating layer was approximately 67 nm. CSW‐g‐PMMA was used as a filler in the melt blending with polypropylene (PP) to prepare PP composites. CSW‐g‐PMMA mainly toughens and enhances the mechanical properties of PP composites in the form of crack bridging, crack deflection and pull‐out effect.Highlights The mechanism of sodium oleate modified calcium sulfate whisker (CSW) has been investigated. One is chemical adsorption that the oleic acid ions are adsorbed on the calcium ions site on the CSW surface in a bridge way. The other is physical adsorption that oleic acid ions and dissolved calcium ions are adsorbed in the form of precipitation on the outer layer of CSW. After the modification of sodium oleate, the active group –C=C– was introduced on the surface of CSW, and then the PMMA long chain polymer was grafted with an in‐situ polymerization to form a PMMA coating layer with a thickness of about 67 nm, which significantly improved the hydrophobicity of CSW surface. After modification with sodium oleate and PMMA grafting, the modified CSW significantly toughened and enhanced the mechanical properties of PP composites in the form of crack bridging, crack deflection and pull‐out effect.

Influence of magnesium and calcium sulfate whisker on crystallization characteristics of poly (butylene adipate-co-terephthalate) and Poly(butylene succinate)

Inorganic fillers of whisker-like morphology are considered promising materials, and they have gained significant attention in recent years as a substitute for glass fibers due to their fibrous surface characteristics and extremely low bulk density. This study selected magnesium sulfate whiskers (MSWs) containing crystal water and pure calcium sulfate whiskers (CSWs) as fillers. They were physically blended with biodegradable polymers PBAT and PBS in a range of 0.1 wt.% to 2 wt.% to form composite materials. The non-isothermal crystallization behavior of the composite materials was studied using differential scanning calorimetry (DSC). The data indicated that with an increase in whisker content, the crystallization temperature (Tc) of composites increased, and the addition of a small amount of whiskers led to a reduction in the half-crystallization time of the composite materials, indicating the crystallization capacity of the materials has been enhanced to varying degrees. Analysis via POM unveiled a consistent pattern of decreased spherulite size and heightened spherulite count with the introduction of whiskers. This phenomenon is ascribed to the whisker fillers’ function as nucleating agents within the polymer matrices, thereby stimulating the crystallization process. Interestingly, the findings suggest that CSWs exert a more significant influence on crystallization than MSWs, likely due to the distinct single fiber morphology of the former filler.

Titanium Dioxide and Calcium Sulfate Whiskers Are Used for the Preparation of High Performance Polypropylene and Reduce White Pollution.

The anti-aging agent TiO2-polyacrylonitrile (PAN) and the mechanical strengthening agent CSW-PAN were prepared by radical polymerization using rutile nano-titanium dioxide (TiO2) and anhydrous calcium sulfate whisker (CSW) as raw materials. The structures of TiO2-PAN and CSW-PAN were characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Simultaneously, the mechanical properties, aging properties, and thermal stability of TiO2-PAN/CSW-PAN/polypropylene (PP) composites were studied, and the results showed that the surfaces of nano-titanium dioxide and calcium sulfate whiskers were successfully grafted with acrylonitrile. Owing to the introduction of new elements, such as acrylonitrile, nano-titanium dioxide and calcium sulfate whiskers have anti-aging properties. In comparison of the impact strength and tensile strength of TiO2-PAN/PP and TiO2-PAN/CSW-PAN/PP before aging, it can be proven that adding CSW-PAN can significantly enhance the mechanical properties of TiO2-PAN/CSW-PAN/PP. After 1000 h of aging, the tensile strength of the ternary composite TiO2-PAN/CSW-PAN/PP was 19.88 MPa when the addition amount of TiO2-PAN and CSW-PAN was 3%. Moreover, the impact strength of the ternary composite material TiO2-PAN/CSW-PAN/PP after 1000 h of aging is even better than that of non-aging pure PP materials, proving that the service life of improved PP products is extended, unnecessary waste and environmental pollution can be relieved, and the needs of specific engineering fields can be met.

Carbonation resistance of recycled fine aggregate concrete reinforced by calcium sulfate whiskers

This study investigates mechanical and carbonation resistance tests conducted on Recycled Fine Aggregate Concrete (RFAC) with three different Recycled Fine Aggregate (RFA) replacement rates and four calcium sulfate whisker (CSW) contents, and investigates the effects of RFA replacement rate and CSW content on the mechanical properties of RFAC and the carbonation resistance of RFAC with calcium sulfate whiskers at different ages of carbonation. The microstructure of CSW-modified RFAC was observed and analyzed by SEM electron microscopy to explore further enhancement and toughening mechanisms of CSW in RFAC, as well as the optimal content of CSW in RFAC. In addition, the carbonation depth of recycled concrete with calcium sulfate beard is modeled based on a quadratic fitting formulation. The test results show that the mechanical properties and carbonation resistance of RFAC would decrease with the increase of the RFA replacement rate. Incorporating CSW can effectively improve the mechanical properties and carbonation resistance of RFAC. At 60 % RFA substitution, CSW at 2 % content has the most significant effect on the mechanical properties and carbonation resistance of RFAC. Microscopic analysis shows that CSW has a bridging effect at the micro-cracks in the concrete matrix, preventing the creation and expansion of micro-cracks in the concrete matrix, thus improving RFAC mechanical properties of RFAC and resistance to carbonation. The predicted results of the carbonation depth model which are constructed from the test data coincide with the results. We can use them to predict and analyze the carbonation depth of the carbonation resistance of recycled concrete.

Improved length of calcium sulfate crystal seeds and whiskers via ball milling and hydration treatment

Elucidating the effect of growth periods on the quality of calcium sulfate whiskers (CSWs) prepared from calcium sulfate dihydrate (DH) is imperative. Herein, crystal seeds and whiskers were prepared from DH in a water–glycerol system. Longer whiskers were obtained from crystal seeds prepared via hydration of DH for 30 s than via ball milling for 5 min followed by hydration for 20 s. The attachment of cetyltrimethyl ammonium bromide and glycerol additives to the whisker tops promoted whisker growth. The whisker sponges exhibited good thermal barrier properties and compression cycle stability.

Enhancing Concrete Mechanical Properties through Basalt Fibers and Calcium Sulfate Whiskers: Optimizing Compressive Strength, Elasticity, and Pore Structure.

To study the effects of basalt fibers (BFs), calcium sulfate whiskers (CSWs), and modified calcium sulfate whiskers (MCSWs) on the compressive strength and dynamic modulus of elasticity of concrete, this paper utilizes Mercury Intrusion Porosimetry (MIP) to measure the microstructure of concrete and calculate the fractal dimension of pore surface area. The results indicate that both CSWs and BFs can increase the compressive strength of concrete. CSWs can enhance the dynamic modulus of elasticity of concrete, while the effect of BFs on the dynamic modulus of elasticity is not significant. The improvement in compressive strength and dynamic modulus of elasticity provided by MCSWs is significantly greater than that provided by CSWs. Both CSWs and BFs can effectively improve the pore structure of concrete and have a significant impact on the surface fractal dimension. CSWs inhibit the formation of ink-bottle pores, while BFs increase the number of ink-bottle pores. Due to the ink-bottle pore effect, the fractal dimension of the capillary pore surface is generally greater than three, lacking fractal characteristics. The compressive strength and dynamic modulus of elasticity of concrete have a good correlation with the fractal dimensions of large pores and transition pores.

Crystallization, thermal properties, rheological properties, mechanical properties, and morphology of thermoplastic polyurethanes/calcium sulfate whiskers composites

The research shows that thermoplastic polyurethane (TPU) which is easy to process has great application potential in practical application. In this study, a calcium sulfate whisker (CSW) with high strength and stability was used as a reinforcing filler to improve the processability of flexible TPU. In this paper, TPU/CSW composites were prepared by the melt blending method, and the effects of modified CSW on the thermal, crystalline, and melt properties, as well as the rheological and mechanical properties of TPU composites were investigated. The results showed that when the mass content of modified CSW was 10%, the maximum values of ΔH c and ΔH m were 222.81°C and 9.24 J/g, respectively, and the thermal properties of the composites were the most stable. When the content of modified CSW is 5%, the maximum impact strength, bending strength, and tensile strength are 50.5 KJ/m2, 38.8 MPa, and 927.7 MPa, respectively, and the mechanical properties of the composites are the best. The excellent stability and high strength of TPU/CSW composites show great promise for various applications in transportation and building materials.

Application of Calcium Sulfate Whiskers to Cement-Based Materials: A Review.

In recent years, significant attention has been paid to the use of calcium sulfate whiskers (CSWs) to enhance the performance of cement-based materials (CBM). This technology has attracted widespread interest from researchers because it enhances the performance and sustainability of CBM by modifying the crystal structure of calcium sulfate. This article summarizes the fundamental properties and preparation methods of calcium sulfate whisker materials as well as their applications in cement, potential advantages and disadvantages, and practical applications and prospects. The introduction of CSWs has been demonstrated to enhance the strength, durability, and crack resistance of CBM while also addressing concerns related to permeability and shrinkage. The application of this technology is expected to improve the quality and lifespan of buildings, reduce maintenance costs, and positively impact the environment. The use of CSWs in CBM represents a promising material innovation that offers lasting and sustainable advancement in the construction industry.