Cycloaliphatic Epoxy Research Articles

Study on the corona aging characteristics of KH570-modified nano-Al(OH)₃ cycloaliphatic epoxy resin in hygrothermal environments

Cycloaliphatic epoxy(CE) resin may experience insulation degradation and pose a threat to the safe operation of equipment when used in high-temperature and high-humidity environment. Therefore, to enhance the corona aging resistance of CE under harsh conditions, this study incorporated γ-methacryloxypropyltrimethoxysilane-modified (KH570) nano-Al(OH)₃ with varying content into the CE. The samples were subjected to corona aging tests under different hygrothermal conditions. The corona aging characteristics of CE in high-temperature and high-humidity environments were analyzed using scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), resistivity, and dielectric loss measurements before and after modification. The results indicate that as humidity increases, the unmodified samples develop pores and cracks on the surface, which leads to an increased water absorption rate and internal hydrolysis. However, with the increase in filler content, the water absorption channels on the sample surface decrease, effectively suppressing chemical moisture absorption and maintaining the stability of the internal chemical structure. Among the various filler contents, the effect was most pronounced at 3%wtCE. Under 65 % RH conditions, the volume/surface resistivity increased by 27.28 % and 26.9 %, respectively, the leakage current decreased by 64.85 %, while the dry and wet breakdown voltages increased by 9.3 kV and 6.85 kV, respectively, and the dielectric loss variation with humidity was reduced. Compared to the unmodified material, KH570-modified nano-Al(OH)₃ has significantly improved the insulation and aging resistance properties of the material under hot and humid corona aging conditions. This study provides a reference for improving the performance of epoxy resins under high temperature, high humidity, and strong electric field conditions.

Characterization of Mechanical Properties and Surface Wettability of Epoxy Resin/Benzoxazine Composites in a Simulated Acid Rain Environment

Despite the robustness of thermosetting coatings in various applications, prolonged exposure to acidic environments can cause gradual deterioration, leading to structural or functional damage. This study investigates composite materials comprised of cycloaliphatic epoxy resin (CER) and benzoxazine (BZ) at three different weight ratios: 50:50, 25:75, and 0:100. These composites were exposed to nitric acid, simulating acid rain, for durations ranging from 1 to 5 h. The specimens were characterized for weight change, mechanical properties (flexural strength and short beam strength), and surface properties (contact angle and contact angle hysteresis). Although minimal changes in the physical and mechanical properties of both homopolymer and copolymer composites were detected after short acid exposure (up to 5 h), surface wettability analysis via static contact angle and contact angle hysteresis revealed more pronounced deterioration. The static contact angle decreased by 24.96% and 28.32% for homopolymer BZ and copolymer BZ-CER composites, respectively. Contact angle hysteresis increased by 19.39% and 27.80% for 5 h acid-exposed homopolymer BZ and copolymer CER, respectively. This study underscores the utility of surface wettability analysis as a valuable tool for monitoring deterioration from acidic aging in polymers, particularly in BZ-CER systems used in structural and high-performance applications.

A transparent, strong, moldable wood laminated composite as a sustainable decorative building material

Delignified wood (DW) retaining its microstructure has increasingly been used as an alternative to synthetic or natural fibers in the preparation of fiber-reinforced composites for novel light-transmitting, high-strength structural materials. In this study, wood laminated composite (WLC) was prepared by impregnating with cycloaliphatic epoxy resin (CAE) and laminating using DW as a continuous reinforcing fiber. Results showed that DW effectively strengthened the resin matrix, increasing the epoxy resin's strength by 25.44 %, while CAE modified the wood's opacity, achieving a transmittance of up to 74.83 %. The mechanical and optical properties of the WLC can be effectively tuned through various lamination combinations. Additionally, due to the UV curing properties of CAE and its infiltration of DW, uncured WLC had long-term shade storage capability and excellent processability. The WLC developed in this study combines good processing, mechanical, and optical properties, making it an attractive option for sustainable home decoration and lightweight structural materials.

Liquid-Solid Interaction to Evaluate Thermal Aging Effects on Carbon Fiber-Reinforced Composites

This study investigated the thermally induced aging effects on a carbon fiber-reinforced composite (CFRP) comprising benzoxazine (BZ) and cycloaliphatic epoxy resin (CER). Herein, we employed various testing methodologies to assess the aging behavior of CFRP samples with differing CER and BZ ratios. Traditional techniques, including weight change quantification and qualitative analysis of surface morphology, reveal that higher CER content correlates with increased aging. Additionally, wettability analysis demonstrates that both BZ and BZ-CER composites exhibit heightened hydrophilicity with thermal aging, potentially exacerbating concerns such as icing and surface erosion. Notably, the BZ-CER composite displays greater hydrophilicity compared to the BZ composite, consistent with weight change trends. These findings underscore the utility of surface wettability analysis as a valuable tool for monitoring thermo-oxidative aging in polymers and their surface behavior in response to fluid interactions, particularly within high glass transition temperature (Tg) BZ-CER systems utilized in structural composite applications.

Curing Behavior and Properties of Active Ester Cured Cycloaliphatic Epoxy Resins

Curing Behavior and Properties of Active Ester Cured Cycloaliphatic Epoxy Resins

Influences of amine/epoxide ratio on cross-linking structure and mechanical properties of cured hydrogenated epoxy resin sheets and single-lap joints

The influence of the amine/epoxide ratio (N–H/Ep.), controlled from 0.5 to 2.0, on the network structure and mechanical properties of cured epoxy resin (CER) was investigated using a cycloaliphatic epoxy and amine components, in a form of sheets and single-lap joints (SLJs). The cross-linking density and glass transition temperature of CER sheet was the highest at 1:1 stoichiometric N–H/Ep. ratio and became lower with being out of the ratio. On the contrary, tensile strength of sheet and shear strength of SLJ monotonically increased and decreased with an increase in amine content, respectively. Excess amine can work as fillers for sheets and made interfacial strength weaken between adherend and adhesive for SLJs. Changing the N–H/Ep. ratio can control the mechanical properties of not only sheets, but SLJs. Comparisons with mechanical properties of sheets and SLJs are quite helpful to design the high-performance adhesive.

Effect of Silica Nanofiller on Thermal-Oxidative Degradation of Epoxy Composites Synthesized by the Sol-Gel Method

Using the sol-gel method, amine-curing polymer silica composites based on cycloaliphatic epoxy resin were obtained. The content of SiO2 filler in the composites was 0.5–10 wt %. The formed mass fractal of silica nanoparticles during the synthesis of composites has a reinforcing effect on the epoxy polymer matrix. The patterns of non-isothermal destruction of polymers and composites in the presence of atmospheric oxygen have been established. At 5 wt % SiO2, the effective activation energy of the main stage of destruction of composites increases from 165 to 254 kJ mol–1. As a result, the rate of weight loss of the samples decreases (the temperature corresponding to 50% weight loss shifts towards higher values by 30°C). The mechanism of high-temperature oxidation of pure polymer and composite with oxygen has been studied. It has been established that the introduction of SiO2 into the composition of composites increases the activation energy of isothermal oxidation of the substrate.

Bio-based hybrid nanocomposites as multifunctional sustainable materials for stone conservation

This study was aimed at developing a sustainable versatile bio-based epoxy-silica material to be potentially employed as hydrophobic and biocidal consolidating product in the field of stone conservation. For this purpose, two hybrid formulations containing 2,2,4,4-tetramethyl-1,3-cyclobutanediol diglycidylether (CBDO-DGE), a cycloaliphatic epoxy precursor derived from the arnica root, together with (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and octyltriethoxysilane (OcTES) as silica-forming additives, were chosen as the basis of the multifunctional material to be finely adjusted and gain biocidal properties. With this goal in mind, different synthetic strategies based on ionic liquids (ILs), essential oils (EOs) and nanoparticles (NPs) doping have been employed. Specifically, dimethyloctadecyl[3(trimethoxysilyl)propyl]ammonium chloride (QAS), tetradecyl phosphonium chloride (QPS) and thymol, as well as cerium-TiO2 NPs and thymol-loaded SiO2 NPs were incorporated into the starting hybrid formulations, during the sol-gel process, to investigate their influence on the network formation. First, distribution studies by scanning electron microscopy/energy-dispersive X-ray (SEM-EDS) analysis were performed, whereas the suitability of each formulation to match the main requirements for a stone conservation material was evaluated in terms of thermostability, hydrophobicity and inhibition of the microbiological growth by a combination of TG-DTA, DSC, dynamic mechanical analysis (DMA), with contact angle and disk-diffusion measurements, respectively. Based on the data analysis, it was observed that the direct incorporation of ILs and EOs had an adverse effect on the ability of GPTMS to act as a coupling agent. This resulted in decreased thermal stability and a 50 % reduction in glass transition temperatures, along with the retention of hydrophilic behavior. In contrast, the inclusion of NPs did not significantly interfere with the hybrid network formation, and effectively maintained the thermo-mechanical and hydrophobic properties of the hybrids within satisfactory parameters. Consequently, both nanocomposite materials were further tested on stone samples by artificial ageing experiments under acidic atmosphere. In view of the results, the hybrid enriched with thymol-loaded SiO2 NPs demonstrate the most suitable thermo-mechanical and hydrophobic properties (Tonset, Tα and CA values of 276 °C, 54 °C and 100°, respectively), as well as a proper biocidal capability against bacteria. Furthermore, the developed material provided effective stone protection, resulting in a 92 % reduction in material loss, while preserving the substrate chromatic characteristics (ΔE 2.23). These findings suggest that the proposed treatment meets the first main requirements for stone conservation.

Radical Afterglow Emission Harnessed by Doping N,N’‐Diaryl‐5,10‐Dihydrophenazines to Epoxy Resins

AbstractDeveloping radical‐induced afterglow emission under ambient conditions is challenging since newly formed radical species are susceptible to air and water. In this work, long afterglow materials (up to 4 s) are realized by doping a series of N,N’‐diaryl‐5,10‐dihydrophenazine (DPP)derivatives into rigid cycloaliphatic epoxy resins (CER). The afterglow is found to result from the interaction between the matrix and the excited states of the dopants through the generation of radical species under continuous UV excitation, which can be regulated by the peripheral functional groups of the N‐phenyl substituents. Density functional theory (DFT) calculations predict that the introduction of electron‐withdrawing groups hinders the afterglow emission, which may be related to the reducing reduction potential and inefficient spin‐orbit coupling (SOC) coefficients. The afterglow emission of the radical‐based systems demonstrates a bright opportunity for information encryption, anti‐counterfeiting, and photolithography.

Synthesis and properties of trifluoromethyl organosilicon cycloaliphatic epoxy monomers for cationic photopolymerization

AbstractThe cycloaliphatic epoxy compounds have been widely used as the monomers in cationic photopolymerization and the fluorine‐modified organosilicon materials combine the merits of both organosilicon and organofluorine. In this work, three trifluoromethyl organosilicon cycloaliphatic epoxy monomers with different chain length (CE‐FSin, n = 3, 6, 9) were designed and prepared by using a facile two‐step synthesis and very competitive raw materials. CE‐FSin showed good ability to cationically photopolymerize. The final conversion of the alicyclic epoxy group of CE‐FSin systems reached up to 84.0% under the irradiation for 900 s. The addition of CE‐FSin enhanced the surface water repellency, heat resistance, elongation at break and glass transition temperature (Tg) of the cured film because of the presence of organosilicon chain and trifluoromethyl group of CE‐FSin. The cured film of CE‐FSi3‐0.5% had the largest water contact angle (105.0°), while the cured film of CE‐FSi9‐0.5% had tensile strength of 0.49 MPa and elongation at break of 68.51% that was three folds as that of the blank control. The addition of CE‐FSin had no obvious influences on the adhesion forces of the cured films, but decreased the pencil hardness.

Advanced 3D printed mini-vascular network for self-healing concrete

Recently, the development of 3D mini-vascular networks has demonstrated their ability to facilitate self-healing in concrete structures. These 3D printed polylactide (PLA) hollow ligament tetrahedral shaped units (TETs) can heal multiple occurrences of damage by releasing a single-component healing agent stored within. To improve the healing efficacy of the concrete-TET system whilst overcoming the potentially short shelf life of single-component healing agents, the TETs design was modified. TETs with co-axial hollow ligaments (d-TETs) suitable for storing bi-component healing agents were manufactured. Different healing agents, including epoxy resin (i.e. cycloaliphatic epoxy resin plus hardener) and sodium silicate in isolation or in combination with either nanosilica or nanolime solution were explored. The d-TETs were effective in storing these bi-component healing agents without them undergoing premature mixing and curing. Moreover, the d-TETs successfully ruptured and released healing agents at a crack width of 0.35 mm. After one damage-healing cycle, significant strength and stiffness recovery was achieved: d-TETs hosting sodium silicate and nano-lime yielded the best strength recovery (25%), whilst most other sodium silicate-based healing agent combinations demonstrated stiffness recoveries of approximately 40%. This demonstrates the efficiency of the d-TETs concept as a system, which allows strength and stiffness recovery despite the limited volume of healing agent.

Cycloaliphatic Epoxy Matrix in the Development of Anticorrosive Coatings Containing Various Modifying Additives

Cycloaliphatic Epoxy Matrix in the Development of Anticorrosive Coatings Containing Various Modifying Additives

Flame-Retardant Cycloaliphatic Epoxy Systems with High Dielectric Performance for Electronic Packaging Materials.

Flame-retardant cycloaliphatic epoxy systems have long been studied; however, the research suffers from slow and unsatisfactory advances. In this work, we synthesized a kind of phosphorus-containing difunctional cycloaliphatic epoxide (called BCEP). Then, triglycidyl isocyanurate (TGIC) was mixed with BCEP to achieve epoxy systems that are rich in phosphorus and nitrogen elements, which were cured with 4-methylhexahydrobenzene anhydride (MeHHPA) to obtain a series of flame-retardant epoxy resins. Curing behaviors, flame retardancy, thermal behaviors, dielectric performance, and the chemical degradation behaviors of the cured epoxy system were investigated. BCEP-TGIC systems showed a high curing activity, and they can be efficiently cured, in which the incorporation of TGIC decreased the curing activity of the resin. As the ratio of BCEP and TGIC was 1:3, the cured resin (BCEP1-TGIC3) showed a relatively good flame retardancy with a limiting oxygen index value of 25.2%. In the cone calorimeter test, they presented a longer time to ignition and a lower heat release than the commercially available cycloaliphatic epoxy resins (ERL-4221). BCEP-TGIC systems presented good thermal stability, as the addition of TGIC delayed the thermal weight loss of the resin. BCEP1-TGIC3 had high dielectric performance and outperformed ERL-4221 over a frequency range of 1 HZ to 1 MHz. BCEP1-TGIC3 could achieve degradation under mild conditions in an alkali methanol/water solution. Benefiting from the advances, BCEP-TGIC systems have potential applications as electronic packaging materials in electrical and electronic fields.

Investigation of cycloaliphatic amine-cured bisphenol-A epoxy resin under quenching treatment and the effect on its carbon fiber composite lamination strength

AbstractThermosetting epoxy resin polymer with cycloaliphatic amines curing agent has been widely used for a composite matrix with carbon fiber reinforcement. The utilization was increased due to the superior performance of this epoxy resin compared to other polymers. However, a changing operational environment has potentially reduced composite performance, which most likely begins with matrix degradation. This research applies thermal treatment by the quenching process sequence to the epoxy resin matrix and its reinforced carbon fiber composite (CFRP). The composite is made by epoxy resin diglycidyl ether bisphenol-A, curing with cycloaliphatic amine as matrix and strengthening carbon fiber mat/woven. Three times quenching treatment was performed by heating the specimen around the glass transition temperature and then dipped immediately in fresh water. After quenching treatment, the epoxy resin shows a reduction in tensile strength and elongation. Under infrared observation, epoxy resin does not significantly show changes in functional groups. Investigation under X-ray refraction also indicates no difference in a crystalline structure; this epoxy resin stays in an amorphous form before and after quenching. In contrast to the matrix, the quenching treatment of the CFRP composite above the epoxy resin s glass transition temperature revealed an increase in the interlaminar shear strength (ILSS). The matrix ductility reduction after quenching should be carefully considered for application in the form of epoxy resin sheets or CFRP composite construction materials.

Redox cationic frontal polymerization: a new strategy towards fast and efficient curing of defect-free fiber reinforced polymer composites.

Frontal polymerization of epoxy-based thermosets is a promising curing technique for the production of carbon fiber reinforced composites (CFRCs). It exploits the exothermicity of polymerization reactions to convert liquid monomers to a solid 3D network. A self-sustaining curing reaction is triggered by heat or UV-radiation, resulting in a localized thermal reaction zone that propagates through the resin formulation. To date, frontal polymerization is limited to CFRCs with a low fiber volume percent as heat losses compromise on the propagation of the heat front, which is crucial for this autocatalytic curing mechanism. In addition, the choice of suitable epoxy monomers and thermal radical initiators is limited, as highly reactive cycloaliphatic epoxies as well as peroxides decarboxylate during radical induced cationic frontal polymerization. The resulting networks suffer from high defect rates and inferior mechanical properties. Herein, we overcome these shortcomings by introducing redox cationic frontal polymerization (RCFP) as a new frontal curing concept. In the first part of this study, the influence of stannous octoate (reducing agent) was studied on a frontally cured bisphenol A diglycidyl ether resin and mechanical and thermal properties were compared to a conventional anhydride cured counterpart. In a subsequent step, a quasi-isotropic CFRC with a fiber volume of >50 vol%, was successfully cured via RCFP. The composite exhibited a glass transition temperature > 100 °C and a low number of defects. Finally, it was demonstrated that the redox agent effectively prevents decarboxylation during frontal polymerization of a cycloaliphatic epoxy, demonstrating the versatility of RCFP in future applications.

Dual curing agents for optimized flame-retardancy and physico-mechanical properties of cycloaliphatic epoxy coating

Higher durability with excellent insulation properties is to be considered an important factor for the formulation of intumescent fire-retardant coating (IFR) against the external environment. In this work, two structurally different hardeners such as cycloaliphatic amine and polyamido amine were used for curing hydrogenated bisphenol-A epoxy resin (DGEHBA) to develop intumescent fire-retardant (IFR) coating for exterior applications. Initially, a differential scanning calorimetry study was carried out to estimate the curing kinetics of DGEHBA resin and the hardeners. The IFR coating was prepared by mixing fire-retardant fillers such as ammonium polyphosphate, pentaerythritol and melamine along with TiO2 pigment in DGEHBA resin. The prepared DGEHBA coating was mixed with two different hardeners individually and their combinations in different weight ratios to make a series of epoxy IFR coatings. The impact of curing on the protection ability and integrity of these coatings was evaluated by analyzing their thermal, fire retardance and physico-mechanical virtues. Furthermore, the coatings were also studied for accelerated aging in humidity, weatherometer, seawater immersion and salt spray chamber to deduce the sustainability of the coatings. We have demonstrated enhancement in both, physico-mechanical and fire-retardant properties by using the above prepared coating compositions.

Effect of temperature and oxygen functional groups on interaction between epoxy resins and graphene surface

Surface interactions between epoxy matrices and graphene nanosheets can directly affect the properties of nanocomposites, and such interactions are crucial to investigate. In this study, molecular dynamics simulation was used to investigate the interaction rate between epoxy thermoset resins (EPON 828, EPON 862, Epoxy Novolac, and Cycloaliphatic Epoxy) with graphene, and Functionalized Graphene with Oxygen Functional Groups. The effect of temperatures and different weight percentage of graphene oxide (1, 3, and 5 wt.%) was studied, and as a result of which it was observed that increasing the weight percentage of graphene oxide improved the interaction energy (adhesion) between epoxy resins and graphene oxide. Also, it decreased the radius of gyration (more contraction of epoxy molecules than graphene oxide nanosheets). In addition, increasing the temperature led to reduction of the interaction energy between epoxy resins and functionalized graphene. Moreover, escalating the temperature did not have any significant effect on the radius of gyration and Epoxy molecules resizing compared to graphene oxide nanosheets. The amount of interaction energy between epoxy resins and pristine graphene is very low in comparison with graphene oxide; therefore, temperature has a small effect on the amount of interaction energy and radius of gyration. Finally, the strongest interaction energy was found to be related to Epoxy Novolac and EPON 862 resins by comparing the interaction energy and radius of gyration between epoxy resins with graphene oxide. Therefore, they were the best candidates for matrixes in epoxy/graphene oxide nanocomposites.

Effect of adsorption, hardener, and temperature on mechanical properties of epoxy nanocomposites with functionalized graphene: A molecular dynamics study

Investigating Epoxy/hardener ratio and adsorption rate in epoxy/graphene oxide nanocomposites is of great importance, since these values can affect on the mechanical properties of the nanocomposite. In this study, molecular dynamics simulation was used to investigate and compare the mechanical properties of epoxy/graphene and graphene oxide nanocomposites (EPON 828, EPON 862, Epoxy Novolac, and Cycloaliphatic Epoxy with GNs and GO). Also, the effect of different weight percentages of graphene oxide (0,1,3 and 5 wt %), different weight percentages of epoxy compared to hardener, adsorption rate, and different temperatures were studied. The results showed that increasing the weight percentage of graphene oxide in epoxy matrices improved the adsorption rate between Epoxy/GO and the strength of nanocomposites. In addition, the amount of Young's modulus slightly decreased with increasing the temperature. Besides, the highest amount of Young modulus was obtained by increasing the weight percentage of epoxy to hardener at 63:37 wt %. Moreover, by comparing the mechanical properties of epoxy nanocomposites at 5 wt % graphene oxide, the highest Young modulus were found to be related to Novolac/GO 4.27 Gpa and EPON 862/GO 4.24 Gpa. This study contributes to a more comprehensive understanding on the behavior of the mechanical properties of epoxy/graphene oxide nanocomposites.

Research of cycloaliphatic epoxy resin and silicone rubber composite insulator interface based on four‐electrode system and temperature rise model

AbstractInterface degradation between mandrel and sheath can cause a decrease in insulation performance and mechanical strength of composite insulators. In this study, the interface ageing properties of cycloaliphatic epoxy resin and silicone rubber composite insulator were compared. A water diffusion test was adopted to simulate the composite insulator ageing in a hot and humid environment. A four‐electrode system was built to detect leakage current at different locations (mandrel, sheath and interface), which is an important basis for evaluating insulator performance. The ageing degree of insulator could be quantitatively characterised by leakage current change. It was found that the infiltrated moisture had a great effect on insulation performance. Based on the water absorption test result, the interface performance of two insulators was mainly influenced by their sheath sealing quality. As an auxiliary evaluation method, temperature rise during the test was recorded using an infrared camera. The experiment results showed that interface degradation was the main factor for the insulation performance decrease of silicone rubber composite insulators. However, insulation level reduction of the cycloaliphatic epoxy resin was caused by the wet sheath. In addition, a model for temperature rise of cycloaliphatic epoxy resin insulators was proposed based on good correspondence between sheath material and insulation. The model incorporated multiple processes such as ageing and heating of insulators, and it can predict the early temperature rise well.

Cover Image, Volume 139, Issue 32

The cover image, prepared by Yuhao Liu, Ying Lin, Liming Wang, and Yaying Xu, shows a silicone prepolymer prepared to modify a cycloaliphatic epoxy resin (CEP) with uniformly distributed solid dispersion phases. The toughness, hydrophobicity, and hydrophobic transfer properties of the CEP were simultaneously improved. This method has potential for applications in outdoor insulation or other waterproof and humidity fields. The proposed mechanism offers a guide on how to design hydrophobic CEP materials. DOI: 10.1002/app.52478