Curing Mechanism Research Articles

Effects of Photoinitiators on Curing Performance of Wood Wax Oil Coating on Wood

With the increasing shortage of petroleum resources and the growing seriousness of environmental pollution, the exploitation and application of bio-based coatings derived from renewable resources have become increasingly important for the woodworking industry. Wood wax oil (WWO) is a new type of bio-based natural coating material that offers an eco-friendly solution for wood protection. This paper focused on the utilization of tung oil and beeswax as the primary raw materials for the preparation of wood wax oil. The WWO was based on the oxidation polymerization of tung oil, which served as the foundation for the preparation process. The effects of the photoinitiator TPO-L on the curing performance of the WWO were investigated, and the curing mechanism of the WWO system induced by photoinitiators was analyzed and characterized by infrared spectroscopy. Through ultraviolet irradiation experiments and coating quality tests, the effects of incremental photoinitiators on the properties of the surface drying time, gloss, color, hydrophobicity, and solution resistance of the treated ash wood were studied. The results indicated that the addition of photoinitiators was beneficial for the rapid polymerization of wood wax oil. A UV light intensity of 30 w was found to be sufficient to initiate the curing process. Specifically, when using TPO-L as the initiator at a concentration of 3 wt%, the surface could be surface-dried within 10 min under UV exposure. Under these curing conditions, wood wax oil coatings based on tung oil with comprehensive curing properties can be obtained. Additionally, adding 6% beeswax to the tung oil can effectively enhance the hydrophobicity of pure tung-oil-based wood protective coatings.

Enhancing the performance of aerated concrete through accelerated curing and waste material integration

In this paper, the mechanical and durability properties of aerated blocks are discussed. Aerated blocks are prepared using different cementitious materials with an alkaline solution in the absence of aluminium powder. The proportions of raw materials are chosen after performing two mix trials P1 and P2, keeping the density of the blocks constant at 800 kg/m3. Each mix is further tested under six curing mechanisms, namely, normal water curing, humidity chamber curing (at 50°C and 70% relative humidity) for 6 h and 10 h, curing by oven drying at 180°C for 6 h and at 80°C for 24 h and using an accelerated curing tank (ACT) at 65°C ± 5°C for 10 ± 2 h; this is termed trial 1. In trial 2, the best curing mechanism is taken and construction and demolition wastes (CDW) are substituted at different proportions in place of fly ash in both the mix proportions. In addition, trial 3 investigates the best mix proportions by substituting glass powder at 50% and 100% with fly ash and CDW, respectively. It is observed from experiments that aerated blocks manufactured with 50% CDW and heat curing by ACT showed high mechanical and durability properties after 7 days of hardening.

Exploiting sugarcane waste molasses and dephenolized cottonseed protein as the promising component for eco-friendly wood-based panel adhesive formulation

ABSTRACT In this study, sugarcane waste molasses (SWM) was utilized as a raw component to prepare an eco-friendly plywood adhesive. The optimization of preparation conditions, examination of thermal curing behavior, and exploration of the adhesive's curing mechanism were investigated. Based on the results, the optimal preparation conditions were determined as follows: the SWM is mixed with dephenolized cottonseed protein (DCP), a mass ratio of 2:1 between SWM and DCP, with a concentration of 75% and the addition of 7.5 wt% ammonium dihydrogen phosphate (ADP). Additionally, the optimal hot-pressing condition involved a temperature of 190°C for 10 min. Under these optimized conditions, the adhesive exhibited a maximum wet shear strength of 1.14 MPa, successfully meeting the China National Standard GB/T9846-2015. The curing behavior of the adhesive was investigated by analyzing thermal analysis and measuring the insoluble mass proportion. As the heating temperature and heating time increased, the insoluble mass proportion gradually rose. Thermogravimetric analysis (TG) showed that the thermal decomposition reaction temperature was 146.4°C and 202.05°C, differential scanning calorimetry (DSC) showed that endothermic reaction occurred at 135.8°C, exothermic reaction occurred at 227.8 °C. Through Fourier-transform infrared spectroscopy (FTIR) and pyrolysis gas chromatography-mass spectrometry (Py-GC/MS), it was observed that the addition of ADP promotes the conversion of sucrose hydrolyzed products into furan compounds and reacts with proteins. Moreover, the amino and carboxyl groups of proteins react with the phenol hydroxyl groups of lignin to form C–N and C–O bonds, a polymer with a cross-linked network is formed.

The Influences and Effect Mechanism of Low Temperature Curing on the Performances of Basic Magnesium Sulfate Cement

The Influences and Effect Mechanism of Low Temperature Curing on the Performances of Basic Magnesium Sulfate Cement

3D printed epoxy/acrylate hybrid polymers with excellent mechanical and shape memory properties via UV and thermal cationic dual-curing mechanism

Fabricating shape memory polymers with complex configurations and high mechanical performance for application as structural materials remains a significant challenge. Here, an epoxy/acrylate hybrid material with remarkable mechanical properties and excellent shape memory performance is fabricated using vat photopolymerization printing technology through photo-thermal dual curing mechanism. The UV-curing component comprises of a polyurethane acrylate and a rigid active diluent to ensure robustness and toughness. Meanwhile, the thermal curing epoxy constituent utilizes a benzylanilinium salt as the cationic initiator for its storage and handling stability throughout the UV curing stage. The interpenetrating polymer network and the unique two-phase molecular microstructure impart the hybrid material with good shape memory and high mechanical properties. Many complex objects are fabricated using vat photopolymerization printing technology and employed in self-deploying antennas, intelligent mechanical grippers, and switches. Combining with excellent printability, mechanical and shape memory properties, the hybrid materials have great potential applications in various fields.

Water migration mechanism during internal curing of cement composites with cellulose microfibers

This study aimed to investigate the internal curing mechanism of cement composites containing cellulose microfibers (CMFs) derived from kenaf stalk bast. The primary test variable was the CMF content, which controlled the amount of water absorbed by the CMFs, thereby facilitating internal curing. The evolution of proton signals from time-domain nuclear magnetic resonance (NMR) was analyzed for the solid phases and various mobile water components during the curing process. The NMR results showed strong correlation with the thermal decomposition and degree of hydration, as determined by thermogravimetry and quantitative X-ray diffraction, respectively. The higher CMF content led to a delayed onset of hydration at early age. Moreover, the internal curing process was supported by the delay in the detection time of the solid-phase signal and an increase in signal intensities of the interlayer water and solid components, indicating the formation of hydrated phases. These insights clarify the significant role of CMFs in enhancing internal curing effects in cement composites.

Effects of the early curing regime on the properties and pore structure of concrete in an environment with high altitudes and low atmospheric pressures

High altitudes have harsh, complex climates and changing environments. These conditions considerably challenge the service life of concrete structures. The engineering quality of concrete structures at high altitudes can be improved by scientific curing regimes; similarly, carbon emissions can be reduced throughout their life cycle. In this paper, the effect of the early curing environment on the macroscopic properties, microstructure, and hydration products of concrete realistically exposed to harsh environments (10–30 °C, RH 20–80 %, 70 kPa) of high altitude was studied. The mechanism of the effect of the early curing environment on the microstructure of the concrete at high altitudes was determined. The concrete performance at high altitudes was investigated regarding the enhancement mechanism of steam curing. At high altitudes, the deterioration of concrete properties was primarily caused by an increase in the percentage of pores sized between 20 and 200 nm and the total porosity. Appropriate steam curing can be employed to enhance concrete hydration in these areas. This process refines the pores in hardened cement paste at the micro-nano scale (20 nm–200 nm and 50 μm–100 μm), ultimately reducing total porosity. Additionally, it alleviates the “aging phenomenon” of the C–S–H gel, which is induced by the low atmospheric pressure environment. The comprehensive performance of concrete in high-altitude areas can be significantly improved by steam curing at 35 °C. Compared with the uncured and sprinkling curing cases, steam curing at 35 °C for 3 days increased the 28-day compressive strength of concrete exposed to the natural environment at high altitudes by 42.8 % and 23.5 %, respectively, reduced the 56-day drying shrinkage strain by 38.7 % and 38.5 %, respectively, and could significantly reduce the risk of concrete cracking at high altitudes.

Comparative study on curing kinetics of MDI-based polyurethanes with different chain length diol curing agents

The difference in the reaction between thermosetting polyurethane (CPU) and binary alcohol system curing agents is crucial for obtaining accurate curing kinetics models and selecting curing agents. Based on a systematic comparison of the reaction activation energies and kinetic models of three different chain length fatty alcohol curing agents, ethylene glycol, 1,4-butanediol, and 1,6-hexanediol, the effect of curing agent chain length on the curing reaction was elucidated. Using differential and integral transformation methods to process non-isothermal DSC tests results, the effect of different chain lengths curing agents on the activation energy of MDI based polyurethane were analyzed. Based on the self-catalytic model, the segmented curing mechanism of the MDI based polyurethane systems were studied, and applicable high-precision segmented kinetic models’ parameters were calibrated. The optimal curing conditions for these systems were determined using extrapolation. The research results indicate that when the curing degree increases to 95 %, the overall activation energy of the MDI/1,4-butanediol system decreases by 47.1 %, accompanied by a faster self-catalytic. However, the activation energies of the other two systems, MDI/propylene glycol system and MDI/1,6-hexanediol system increased by 62. % and 295.0 %, respectively. This slows down the reaction rate of the two systems, which was 7.8 % and 10.9 % slower than the MDI/1,4 butanediol. heir molecular cross-linking network limits the diffusion ability of their chains and reduces the self-catalysis, resulting in slow reactions. These results will provide theoretical guidance and reference for the material formulation, process optimization of MDI based polyurethane actual curing production.

Cold atmospheric plasma induces the curing mechanism of diabetic wounds by regulating the oxidative stress mediators iNOS and NO, the pyroptotic mediators NLRP-3, Caspase-1 and IL-1β and the angiogenesis mediators VEGF and Ang-1

It has been demonstrated that cold atmospheric plasma (CAP) accelerates the wound healing process, however the underlying molecular pathways behind this effect remain unclear. Thus, the goal of the proposed investigation is to elucidate the therapeutic advantages of CAP on angiogenesis, pyroptotic, oxidative stress, and inflammatory mediators during the wound-healing mechanisms associated with diabetes. Intraperitoneal administration of streptozotocin (STZ, 60 mg/Kg) of body weight was used to induce type-1 diabetes. Seventy-five male mice were randomized into 3 groups: the control non-diabetic group, the diabetic group that was not treated, and the diabetic group that was treated with CAP. The key mediators of pyroptosis and its impact on the slow healing process of diabetic wounds were examined using histological investigations employing H&E staining, immunohistochemistry, ELISA, and Western blotting analysis. Angiogenesis proteins (VEGF, Ang-1, and HO-1) showed a significant decline in expression concentrations in the diabetic wounds, indicating that diabetic animals' wounds were less likely to heal. Furthermore, compared to the controls, the major mediators of pyroptosis (NLRP-3, IL-1β, and caspase-1), oxidative stress (iNOS and NO), and inflammation (TNF-α and IL-6) have higher expression levels in the diabetic wounds. These factors substantially impede the healing mechanism of diabetic wounds. Interestingly, our results disclosed the therapeutic impacts of CAP treatment in the healing process of diabetic wounds via significantly regulating the expression levels of angiogenesis, pyroptosis, oxidative stress and pro-inflammatory mediators. Our findings demonstrated the curative likelihood of CAP and the underlying mechanisms for enhancing the healing process of diabetic wounds.

Internal curing and its application to alkali-activated materials: A literature review

Alkali-activated materials (AAM) are considered as promising alternative to Portland cement, as they can utilize industrial by-products or wastes as precursors and contribute to reducing CO2 emissions. However, poor volume stability, especially in the case of alkali-activated slag (AAS) systems, remains a significant obstacle in their large-scale application. In recent years, internal curing has gained increasing attention and has been introduced into the AAM system. This review paper provides an overview of the mechanism of internal curing, common internal curing agents, with a particular focus on the most promising agent—superabsorbent polymers. It also explores the limitations associated with the AAM systems and the advancements made in the internal curing technique within AAM systems. The introduction of voids by internal curing agents typically has a negative impact on mechanical properties. However, this can be (partially) counteracted by the continuous water release during internal curing which promotes hydration. While the effect of internal curing in reducing autogenous shrinkage of AAM systems has been well-established, the effect on drying shrinkage described in different studies varies widely, with some articles even suggesting a negative impact.

Experimental study on the development mode and evolution mechanism of sodium silicate solidified sand under different temperatures and curing paths

Water glass, which can be cured by rapid dehydration, is an ideal environmentally friendly material for engineering grouting solidification and ecological environment restoration. The curing efficiency of water glass at room temperature was low, the curing mechanism and strength characteristics at high temperature were not clear, and the engineering applicability and optimal curing methods were to be explored. In this paper, 10 curing paths were designed within 100 °C. The mechanical and acoustic characteristics of water glass-cured sandy soils were tested by uniaxial compressive tests and acoustic emission (AE). The relationship between strength, wave velocity and curing age was established based on the “logistics” model. The characteristic parameter “Q” value was proposed based on the AE characteristic value. Combined with the results of scanning electron microscopy (SEM), the solidification evolution process was revealed in terms of gel structure, crystal morphology and pore space. The process of water glass curing sandy soil was divided into a “strength rising period” and a “strength deterioration period”. The enhancement and weakening effects of high temperature on the gel layer were stronger than those at room temperature. The longer the room temperature curing time is, the weaker the effect of high temperature on the specimen. After high-temperature curing, the maximum strength of the specimens increased by 107.85 %, and the strength growth rate and strength deterioration rate increased by 586.34 % and 3738.79 %, respectively. The conversion rate of the gel under high temperature conditions determined the strength of the specimen. The rate of strength deterioration of the specimen was determined by the hardening effect of the undehydrated gel and the excessive dehydration effect of the rigid gel.

Optimization, formation, and evolution of the photoinduced curing gradients and in-situ lamellar gaps in additive manufacturing of ZrO2 ceramics: From curing to sintering behaviors

The photoinduced curing gradients and in-situ lamellar gaps were related to the three-dimensional curing mechanism of stereolithography and researched in this work. Based on the photocuring mathematic theories presented by our team, photoinduced curing gradients were influenced by printing parameters such as laser power and frequency, scanning angle, and printing thickness. Among these curing gradients, the inadequate curing area was the main factor affecting the surface quality and physical properties of ceramics. The in-situ lamellar gaps were derived from the inadequate curing area. The lamellar gap size of green bodies was enlarged in brown bodies (sintering at 1170 ℃) and shrunk in sintered bodies (sintering at 1500 ℃). The correlations between the surface quality and printing parameters were clarified by establishing mathematical formulations of the lamellar gap size. Furthermore, anisotropic volume shrinkage, anisotropic surface topography, and density and hardness evolutions were associated with the wrapped particle density differences induced by the photoinduced curing gradients. Finally, the optimal printing parameters (75% of laser power, laser frequency of 150 kHz, scanning angle of 90º, printing thickness of 25 μm, and scanning speed of 2.5 m/s) were obtained by the orthogonal experimental analysis. This study provides a distinct understanding of the high-quality forming and extreme-performance manufacturing of stereolithography.

Preparation and reaction mechanism of low environmental load mud solidification agent from multivariate solid waste

Utilizing various industrial solid waste to replace cement to prepare mud solidification materials could achieve energy conservation, carbon reduction and sustainable development. This research conducted solidification mud (SM) experiments using solidification agent (SA) compounded by mixing five types of solid waste. The focus was on studying the performance of SA and SM in the presence of different activators, as well as the influence of different activators on the SA curing mechanism. The results indicate that the SA and SM specimens with 3.0% Na2SiO3 addition had the highest compressive strength values at 1 d and 28 d, respectively. In addition, the microscopic test analysis showed that when 3.0% Na2SiO3 was added, the hydration activity of SA was relatively high, and the continuous distribution of cluster gel in the hydration product made its overall structure more compact.

Research on reuse of shield soil dregs on synchronous grouting materials and its application

Shield tunnel construction will produce a large amount of soil dregs. Transporting soil dregs directly to landfills raises costs and CO2 emissions. In this paper, the shield tunnel of Intercity from Shenzhen to Huizhou is taken as an example, based on the special treating agent of shield soil dregs, the soil dregs were prepared as synchronous grouting material. The working performance and mechanical properties of soil dregs grouting material were studied. The optimal dosage of the treating agent was proposed, and the curing mechanism of the soil dregs synchronous grouting material was analyzed. The soil dregs grouting material was applied to practical engineering, and the application effect was verified by surface subsidence monitoring. The results showed that the setting time, bleeding rate, stone rate and compressive strength of the soil dregs grouting material were better than cement mortar grouting material. The treating agent realized the cementation of soil particles through the synergistic effect of epoxy resin and nano-SiO2, and the optimum dosage is 0.02 % of the solid component. The maximum surface settlement of the soil dregs grouting construction section was 10 mm, which is smaller than the maximum surface settlement of the cement mortar grouting section. Through the life cycle assessment (LCA) method, the CO2 emission reduction capacity of the soil dregs synchronous grouting material was analyzed. The soil dregs grouting material reduced the production and transportation of fly ash and bentonite, and reduces the outward transportation of soil dregs. The use of 1 t soil dregs synchronous grouting material can reduce 59.05 kg CO2 emission.

The roles played by anionic and cationic species in the curing process of aromatic nitrile resins

Understanding the curing mechanism of aromatic nitrile (AN) resins is crucial for improving their curing efficiency. Blending the Bronsted acid-containing aromatic nitrile monomers (ACN) and Bronsted base-containing aromatic nitrile monomers (BCN) is a novel approach that simultaneously lowers the melting point and rapid curing reaction temperature of AN resins. To investigate the impact of anionic and cationic species on the curing behavior of ACN-BCN blends, a series of ACN-BCN blends were designed and synthesized. DSC and TGA results demonstrated a significant improvement in the curing efficiency when ACN and BCN blended, the curing temperature decreased by more than 50 ℃, accompanied by a decrease in melting point. According to the DMA results, the Tg of the cured substance of the system can reach 405 ℃ at the curing temperature of 325 ℃. The curing behaviors of ACN-BCN blends were studied through thermal analysis and spectroscopic analysis, which indicates that cationic species can polarize the cyano rather than attack the cyano groups, promoting their curing reaction. Moreover, it was determined that while cationic species play a polarizing role on the cyano, active anionic species attack the cyano, serving as the rate-determining step in the curing process of ACN-BCN blends.

Design, synthesis and curing mechanism of two novel photothermal dual-curing adhesives for propellants and explosives

Photothermal dual-curing adhesive is not only required to realize the basic curing function, but also has the characteristics of rapid setting and strong curing, which possesses a vital role in the molding speed, stability and structure integrity for 3D-printed propellants and explosives. Herein, the acrylate hydroxyl terminated polybutadiene, as novel photothermal dual-curing binders, were designed and synthesized utilizing cationic ring opening polymerization and active monomer mechanism as the strategy of photothermal dual-curing reaction. The mechanical properties and thermal stability of the photothermal dual-curing elastomers were systematically investigated. The results suggested that the target MAHTPB(Acrylate hydroxy‑terminated polybutadiene)-based adhesives could be cured rapidly within 5 s under UV light irradiation and completely cured in 1.5 h under heating conditions. Specifically, the elastomer film formed by MAHTPB-based photothermal dual-curing has a tensile strength of 4.63 MPa and an elongation of 386%, which exhibits stronger mechanical properties than the elastomer film formed by single photo- or thermal-curing. As a result, the synthesized photothermally cured adhesives have performed 3D printing experiments and achieved relatively satisfactory printing effects. Our study aims to solve the problems of short photocuring time, slow curing rate and incomplete curing for traditional photocuring, which lays a solid foundation to achieve rapid prototyping and precise performance control in 3D printing of propellants and explosives.

The green catalyst: Role of hemp fibers in the curing reaction of bio-based epoxy composites

Understanding the curing behavior of epoxy is a critical aspect in the production of epoxy-based composite and pivotal for process optimization. This study focusses on evaluating the curing kinetic parameters of hemp fiber/bio-epoxy composite at different fiber loading (0–30 wt%). The apparent activation energy was determined using Vyazovkin model. The results revealed an intricate chemistry between hemp fibers and bio-epoxy curing mechanism. The activation energy decreased upon the addition of fibers, indicating the catalytic effect of hemp fibers in the curing kinetics of epoxy resin. Further, at low fiber loading exhibiting augmented curing reaction up to 15 wt% fiber loading, whereas a decreased trend was observed thereafter. As a result, the curing time required to cure the bio epoxy was reduced notably when the fiber loading was less than 15 wt%. Hemp fibers with excellent functional groups such as hydroxyl moieties that actively facilitated the curing reaction, providing insight into their role of augmenting curing efficiency. This research provides crucial insights into tailoring the curing conditions and augment the process control efficiency in the manufacturing of thermoset composites.

Cure behavior and mechanism of cyanate ester with aromatic amines at room temperature

Herein, the catalytic effects of aromatic amines with different structures on the room temperature curing of bisphenol E cyanate (BECy) have been studied using differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectroscopy. Our results revealed that the mixed amine comprised of aniline and N,N-dimethyl-p-phenylenediamine (AN/NNDPA) bearing primary amino groups in its structure was a highly effective catalyst for the room temperature curing of cyanate esters. When the cyanate ester and mixed amine were combined at a molar ratio of 100:5 and cured at room temperature for 5 days, the curing degree of BECy resin reached 79.7%. The room temperature curing mechanism of the BECy-AN/NNDPA system was investigated using pyrolysis gas chromatography-mass spectrometry (PY GC-MS). Our results showed that the formation reactions of the intermediate structure and cyclotrimerization reactions occurred during the room-temperature curing process. The activation energies of BECy and different aromatic amine systems at different heating rates were determined using non-isothermal DSC. The results further demonstrated the catalytic effect of AN/NNDPA on the cyanate ester curing reaction. BECy-AN/NNDPA cured at room temperature has suitable heat resistance and a 5% weight loss temperature (Td5) of 361°C.

Mechanical Properties of Fiber-Reinforced Permeable Geopolymer Concrete.

In this paper, permeable geopolymer concrete with high compressive strength and permeability is prepared using alkali-activated metakaolin as a slurry, and its mechanical properties are reinforced by adding steel fibers. The influencing factors of the strength, porosity and permeability coefficient of the fiber-reinforced permeable geopolymer concrete, as well as its microstructure and curing mechanism, are determined by conducting an unconfined compressive strength test, scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. The test results show that, under the water permeability required to meet the specification conditions, when the alkali activator modulus is 1.4 and the activation-to-solid ratio is 0.9, the effect of metakaolin activation is the most obvious, and the unconfined compressive strength of the permeable geopolymer concrete is the highest. Moreover, the paste formed via the alkali activation of metakaolin contains a large number of silica-oxygen and aluminum-oxygen bonds with a dense and crack-free structure, which enables the paste to tightly combine with the aggregates; the strength of the permeable geopolymer concrete is early strength, and its strength at a curing age of 3 days is the highest. The strength at a curing age of 3 days can reach 43.62% of the 28-day strength; the admixture of steel fiber can effectively improve the strength of the permeable concrete, and with an increase in the amount of admixture, the strength of the fiber shows a trend of increasing, and then decreasing. Under the conditions of this test, a volume of steel fiber of 0.3% enables the optimum unconfined compressive strength to be reached.

Experimental Study on the Curing Mechanism of Red Mud-Based Stabilized Soil Co-Modified by Nano-SiO2 and Gypsum.

In order to effectively utilize red mud and reduce its occupation of land resources, as well as its impact on the environment, experiments were conducted to develop stabilized soil materials using nano-SiO2 synergistically modified red mud and to investigate the curing mechanism of stabilized soil. The unconfined compressive strength, microscopic morphology, and curing mechanism of the red mud-based stabilized soil materials with different amounts of modified materials were investigated. The test results show that after 7 days of curing, the unconfined compressive strength of red mud-based stabilized soil meets the compressive strength requirement of road base material when nano-SiO2, gypsum, and cement are synergistically modified. In such cases, the soil structure has the lowest fracture rate and the best structural compactness when the amount of nano-SiO2 is 1%. It is found that the needle-like and columnar calcium alumina in the modified red mud-based stabilized soil increases, and the binding energy of hydration product ions in the modified material is improved. The chemical curing mechanism of modified red mud-based stabilized soil includes hydration reaction, pozzolanic reaction, promotion effect of nano-SiO2, and enhancement effect of gypsum. On this base, a model of the early start hydration process of red mud-based stabilized soil promoted by nano-SiO2 is established.