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Developing effective latent curing agent for rapid curing of epoxy resins at low temperatures remains challenging. This study reports a latent curing agent, ortho‐cresol phenolic epoxy resin‐bisphenol A (EOCN‐BPA), prepared through the addition reaction of o‐methyl phenolic epoxy resin with BPA. When blended with dicyandiamide (DICY) in a 1:3 molar ratio, EOCN‐BPA/DICY is used to cure a linear epoxy phenolic novolac (EPN) resin (epoxy equivalent: 550 g eq−1, softening point: approximately 82°C), at an onset curing temperature of 90°C, which is considerably lower than the onset curing temperature of DICY with EPN (160°C). However, EOCN‐BPA does not react with EPN without a catalyst. Therefore, this latent curing system is successfully applied in powder coatings, rapid curing at 120°C within 3 min without an additional catalyst, outperforming the EPN/EOCN‐BPA system using cocatalyst 2‐methylimidazole. Consequently, DICY catalyzes the curing reaction between the phenol hydroxyl group and epoxy resin and participates in it. The prepared powder coating exhibits excellent storage stability, maintaining its properties for over 3 months at room temperature. These findings demonstrate the excellent latent properties of EOCN‐BPA/DICY, highlighting its potential as a highly effective latent curing agent. [ABSTRACT FROM AUTHOR]

Due to the intricate and volatile nature of the service environment surrounding prestressing anchoring materials, stress corrosion poses a significant challenge to the sustained stability of underground reinforcement systems. Consequently, it is imperative to identify effective countermeasures against stress corrosion failure in cable bolts within deep underground environments, thereby ensuring the safety of deep resource extraction processes. In this study, the influence of various coatings on the stress corrosion resistance of cable bolts was meticulously examined and evaluated using specifically designed stress-corrosion-testing systems. The specimens were subjected to loading using four-point bending frames and exposed to simulated underground corrosive environments. A detailed analysis and comparison of the failure patterns and mechanisms of specimens coated with different materials were conducted through the meticulous observation of fractographic features. The results revealed stark differences in the stress corrosion behavior of coated and uncoated bolts. Notably, epoxy coatings and chlorinated rubber coatings exhibited superior anti-corrosion capabilities. Conversely, galvanized layers demonstrated the weakest effect due to their sacrificial anti-corrosion mechanism. Furthermore, the effectiveness of the coatings was found to be closely linked to the curing agent and additives used. The findings provide valuable insights for the design and selection of coatings that can enhance the durability and reliability of cable bolts in deep underground environments. [ABSTRACT FROM AUTHOR]

Mycelium-based composites are a promising avenue for innovating sustainable materials from the hyphae of fungi. This study focuses on the use of fibers from four local fungal species, namely, Pleurotus ostreatus, Pleurotus sajor-caju (Fr. Singer), Auricularia auricula-judae, and Schizophyllum commune Fr., to produce mycelium-based composites from water hyacinth. An inoculum of each of the mushroom species was cultivated on PDA medium at 25 and 30 °C to determine the optimal temperature based on the growth rate. The obtained optimal condition was used to grow the fungi on water hyacinth (WH) mixed with rice bran in different proportions (100% WH, 70% WH, and 50% WH) with various numbers of fungal inocula (10, 20, and 30 plugs). The obtained composites were coated with a solution of either starch, chitosan, or epoxy resin. Schizophyllum commune Fr. exhibited the highest growth rate and fiber density, with a growth rate of 1.45 ± 1.92 mm/day at 30 °C. Ten inocula of Schizophyllum commune Fr. incubated at 30 °C for seven days on a mixture of 50% WH and 50% rice bran gave the optimal composite. Coating the obtained composite with chitosan improved its mechanical properties, but coating it with epoxy resin improved its water absorbency. Buried in soil, the composite coated with a chitosan solution decomposed within 30 days. The results indicate that Schizophyllum commune Fr. can be used as a binder to produce mycelial composites on a substrate of WH mixed with rice bran. The implications of these results will enable the further development and tuning of mushroom-based materials, especially for the production of sustainable bio-construction materials derived from local mushrooms and bio-waste. [ABSTRACT FROM AUTHOR]

Polyether polyols can improve the performance of waterborne epoxy curing agent. In this paper, intermediates were synthesized from polyether triols with epoxy resin E‐51 and introduced into the epoxy curing agent by reacting with TETA. This paper focuses on the process of synthesizing the intermediates. The 2K waterborne epoxy coating film prepared with polyether triols‐modified waterborne epoxy curing agent exhibits desirable corrosion protection capacity and neutral salt spray resistance up to 600 h. In addition, the 2K waterborne epoxy coating film prepared using the modified waterborne epoxy curing agent with polyether triols displayed improved surface appearance, mechanical properties, and water resistance. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) is considered as one of the most promising corrosion inhibitors because of its unique redox and environmental stability. Pyridine and its derivatives can chelate metal ions during corrosion, forming an inert protective layer on the metal surface to achieve the anticorrosion effect. Therefore, polyaniline is combined with pyridine together to achieve deep anticorrosion in this work. 4‐((2,2′:6′,2″‐terpyridin)‐4′‐yl)aniline (TPY) and 1,3,5‐benzenetricarbonyl chloride (TMC) were applied to synthesize a novel corrosion inhibitor N1, N3, N5‐tri (4‐((2,2′: 6′, 2′‐tri‐pyridine)‐4′‐yl) phenyl) benzene‐1,3,5‐tri‐formamide (TBT). Then, TBT was in situ loaded onto the PANI surface to obtain the composite TPANI. The TPANI was successfully dispersed in epoxy resin (EP) at various dosages to prepare composite coatings. Electrochemical impedance spectroscopy and salt fog tests were employed to evaluate the performance of the coatings. After experimentation, we discovered that when the TPANI content was 0.25 wt%, the impedance value remained stable at 5.83 × 109 Ω cm2 after immersing the coatings in a 3.5 wt% NaCl solution for 28 days. In contrast, the EP coating exhibited a resistance decrease ranging from 9.56 × 109 to 7.8 × 108 Ω cm2 within the same soaking time, decreasing by an order of magnitude, while the TPANI‐0.25% coating still maintaining a high order of magnitude. These results indicated that the TPANI filler effectively preserved long‐term stability and provided persistent protection against corrosion. The protective mechanism of TPANI composite coatings was further elucidated through detailed analysis. Overall, the incorporation of TPANI into the epoxy resin yielded promising results, demonstrating its potential as an effective corrosion inhibitor for protective coatings. [ABSTRACT FROM AUTHOR]

Preparation of hydrophobic coatings is still a challenge for researchers in various fields of science. One of the easiest ways consists of the use of special modifiers. However, usually such modifiers are poorly compatible with organic polymeric matrixes, which leads to segregation of modifiers and deterioration of coating properties. In this work, we have synthesized a number of organosilicon copolymers and studied their compatibility with epoxy matrix and hydrophobic efficiency. It was shown that the increase of phenyl-containing units leads to increase of compatibility but decreases hydrophobic efficiency. Addition of small amounts of such modifiers into commercial epoxy paint material can lead to an increase of contact angle of the final coating from 63 to 87° without deterioration of other physico-mechanical properties. These results open new perspectives in preparation of organosilicon hydrophobic modifiers with directed properties for fields of application such as paints and coating materials. [ABSTRACT FROM AUTHOR]

Dual microcapsule systems, especially those based on the polyurea matrix, have emerged as pivotal components driving innovation in self-healing materials, thanks to the intrinsic properties of polyurea, primarily diamine and diisocyanate, rendering it an optimal choice for enhancing self-healing coatings. However, the encapsulation of polyurea components is fraught with substantial technical hurdles. Addressing these challenges, a novel methodology has been devised, leveraging n-heptane as a solvent in the liquid diamine emulsion process to facilitate the synthesis of diamine microcapsules. These microcapsules exhibit a uniform spherical morphology and a robust shell structure, with an encapsulated core material ratio reaching 39.69%. Analogously, the encapsulation process for diisocyanate has been refined, achieving a core material percentage of 10.05 wt. %. The integration of this bifunctional microcapsule system into diverse polymeric matrices, including epoxy resins and polyurethanes, has been demonstrated to significantly enhance the self-healing efficacy of the resultant coatings. Empirical validation through a series of tests, encompassing scratch, abrasion, and saltwater immersion assays, has revealed self-healing efficiencies of 21.8% and 33.3%, respectively. These results indicate significant improvements in the durability and self-repair capability of coatings, marking a notable advancement in self-healing materials with promising potential for tailored applications in automotive, aerospace, and construction industries. [ABSTRACT FROM AUTHOR]

Corrosion is a major problem that can lead to the degradation of metal structures. In this study, we developed a novel corrosion-protective coating for metal substrates based on a modified epoxy acrylate formulation reinforced with halloysite nanotubes (HNTs). Epoxy acrylate oligomers were first synthesized through the acrylation of epoxy using acrylic acid, followed by copolymerization with butyl methacrylate/vinyl acetate monomers to produce grafted epoxy acrylates (GEA). HNTs were then incorporated into the polymeric dispersion at weight loadings of 1%, 1.5%, and 2%. The corrosion resistance and waterproofing properties of the coatings were evaluated. The results showed that steel samples coated with HNTs-modified GEA showed no signs of rusting even after 16 days of immersion in a corrosive solution, whereas those coated with GEA alone showed rusting after only 9 days. These results demonstrate the effectiveness of HNTs- modified GEA coatings in protecting steel surfaces against corrosion. The coatings are also water-resistant and can be easily applied. This work provides a new approach to developing corrosion-protective coatings for metal substrates. [ABSTRACT FROM AUTHOR]

This work investigates the stick–slip phenomenon during sliding motion between solid lubricant-impregnated epoxy polymer-coated steel bars and AISI 52,100 steel balls. An acoustic sensor detected the stick–slip phenomenon during the tribo-pair interaction. The wear characteristics of the workpiece coated with different epoxy coatings were observed and scrutinized. The RMS values of the acoustic sensor were correlated with the frictional coefficient to develop a standard based on the acoustic sensor, leading to the detection of the stick–slip phenomenon. As per the findings, the acoustic waveform remained relatively similar to the friction coefficient observed during the study and can be used effectively in detecting the stick–slip phenomenon between steel and polymer interaction. This work will be highly beneficial in industrial and automotive applications with a significant interaction of polymer and steel surfaces. [ABSTRACT FROM AUTHOR]

Co3O4 nanoparticles (Co3O4-NPs) are synthesized using the facile solvothermal method. FT-IR and XRD spectroscopic analyses verify the creation of cobalt oxide nanoparticles with an average size of 13.20 nm. Furthermore, Zeta potential assessments were carried out to identify the electrical charge of the surface of the produced Co3O4-NPs, which was found to be -20.5 mV. In addition, the average pore size of Co3O4-NPs is 19.8 nm, and their BET surface area is 92.4 m/g. The study also concerned the effect of Co3O4-NPs on epoxy's improvement of mechanical and corrosion protection for carbon steel in salt solution. By including Co3O4-NPs in an epoxy (EP) coating, corrosion is effectively prevented by non-permeable protective coatings that effectively reduce the transfer of corrosion ions and oxygen. [ABSTRACT FROM AUTHOR]

Waterborne polymer–cement coatings have been widely applied in building materials due to their organic solvent-free nature, low cost, and eco-friendliness. However, these coatings can easily crack during the drying process as a result of construction environment factors, compromising the barrier performance of the coating and limiting its large-scale application. In this study, a dual-shell self-healing microcapsule was developed, which can effectively heal damage on a macro scale in waterborne polymer–cement coatings. Specifically, this dual-shell self-healing microcapsule was designed with a silica gel shell and a tannic acid–cuprum (TA–Cu) double-shell structure embedded with an epoxy resin (EP) healing agent, which was successfully fabricated via a two-step in situ polymerization. This silica gel shell self-healing microcapsules can effectively load into waterborne polymer–cement coatings. As the coating dries and solidifies, the silica gel shell of the microcapsule also becomes loose and brittle due to dehydration. This improves the mechanical initiation efficiency of the microcapsules in the coating. This study provides a novel approach for the application of self-healing microcapsules in waterborne coating systems, which can significantly reduce cracking during the drying process of waterborne polymer–cement coatings and improve the service life of the coating under complex conditions. [ABSTRACT FROM AUTHOR]

Recently, photocurable coatings are being used frequently. However, it is worth mentioning that the use of photopolymerization has its drawbacks, especially in the case of curing coatings on three-dimensional surfaces and in places that are difficult to access for UV radiation. However, it is possible to develop a system in which UV technology and thermal methods for curing coatings can be combined. Moreover, the obtained resins are derived from low-viscosity epoxy resins or diglycidyl ethers, making them an ideal building material for photopolymerization-based three-dimensional printing techniques. Due to the need to improve this method, a series of epoxy (meth)acrylates containing both epoxy and (meth)acrylate groups were obtained via the addition of acrylic or methacrylic acid to epoxy resin, diglycydylether of bisphenol A epoxy resin (DGEBA), cyclohexane dimethanol diglycidyl ether (CHDMDE) and neopentyl glycol diglycidyl ether (NPDE). The structures of the synthesized copolymers were confirmed through spectroscopic analysis (FTIR) and studied regarding their nonvolatile matter content (NV) and acid values (PAVs), as well as their epoxy equivalent values (EEs). Due to the presence of both epoxy and double carbon–carbon pendant groups, two distinct mechanisms can be applied: cationic and radical. Hence, the obtained resins can be cured using UV radiation with thermally appropriate conditions and initiators. This type of method can be used as a solution to many problems currently encountered in using UV technology, such as failure to cure coatings in underexposed areas as well as deformation of coatings. Synthesized epoxy (meth)acrylate prepolymers were employed to formulate photocurable coating compositions. Furthermore, the curing process and properties of cured coatings were investigated regarding some structural factors and parameters. Among the synthesized materials, the most promising are those based on epoxy resin, characterized by their high glass transition temperature values and satisfactory functional properties. [ABSTRACT FROM AUTHOR]

Biomass resources possessed the advantages of being natural, renewable, abundant, inexpensive, and easy to degrade. Therefore, fabricated bio‐based UV‐curable materials have gradually attracted much more attention, which meet the requirements of sustainable development and save petrochemical resources. In this paper, cardanol was modified to synthesize radical reactive diluent and hybrid reactive diluent by a facial method and was used to adjust the viscosity and reduce the volume shrinkage of UV‐curable epoxy acrylic resin. The structure–activity properties and UV‐curing kinetics of the obtained UV‐curable materials were clarified, and the anti‐shrinkage mechanism was also explored. In addition, the obtained cardanol‐based materials were compared with petroleum based diluent methyl methacrylate (MMA) and application for UV‐curable coatings. The volume shrinkage of the cardanol‐based reactive diluents was 3.5% and 2.1%, respectively, which were lower than MMA (4.6%). The CC conversion of the cardanol‐based reactive diluent exhibited the highest value of 79.6%. This work provided a specific theoretical basis for the subsequent design and application of bio‐based UV‐curable resins. It is of certain significance to the alleviation of the shortage of petrochemical resources and the sustainable development of the UV‐curable coating industries. [ABSTRACT FROM AUTHOR]

In this work, polyaniline-cellulose nanofiber (PANI-CNF) nanocomposites were prepared by in-situ polymerization of aniline on 2,2,6,6-tetramethyl1-piperidinyloxy (TEMPO) oxidized CNFs. Fourier transform infrared spectroscopy and transmission electron microscope demonstrate the successful polymerization of aniline on CNFs. The PANI-CNF nanocomposites were added as nanofillers to waterborne epoxy resin (WER) in different proportions. The composite coatings with different contents of PANI-CNFs were prepared by fabricating the mixture on the Q235 steel sheets. The corrosion resistance of different coatings was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. The results confirmed that composite coatings containing 0.5% PANI-CNF exhibit the optimum anticorrosion behaviors and best corrosion resistance, which shows the lowest corrosion current density (1.788 * [10.sup.-7] A/[cm.sup.-2]) and highest corrosion potential (-0.458 V). In addition, PANI-CNF can significantly enhance the anticorrosion performance of WER coatings and maintain a high value even after 40 days of immersion in NaCl solutions. The above performances are attributed to the synergistic effect of the barrier effects and the passivation mechanism. Therefore, the bio-based composite materials developed in this work are promising in enhancing the corrosion protection of mild steel, which is essential for the sustainable development of waterborne coatings. KEYWORDS anticorrosive coating, cellulose nanofiber, nanocomposite, polyaniline, waterborne epoxy resin, 1 | INTRODUCTION Metals are very important and the most used materials in modern life and industry due to their competitive prices, good mechanical performances, and high recyclability. However, most [...]

Crystallization of bisphenol A (DGEBA)- and bisphenol F (DGEBF)-based epoxy resins is a natural property of these oligomers. However, manufacturers of coatings and other systems based on these epoxy resins are making efforts to slow down the crystallization process as much as possible, thereby extending the shelf life and improving the competitiveness of their products. This paper focuses on the kinetics of the crystallization process of epoxy resins and the effect of the presence of a certain degree of crystallinity on selected parameters of epoxy-based materials. Furthermore, an analysis of the impact of a certain degree of crystallinity of the epoxy base on the resulting coating parameters was carried out. The highest value of crystallinity (17%) was achieved in the sample containing the highest proportion of DGEBF in the crystallization phase "c", and the enthalpy of melting (Ht) of the crystalline DGEBF sample was 6.3 J/g. Mechanical parameters as well as chemical and thermal resistance of hydrophobic epoxy systems were investigated. The best abrasion resistance (1.5 cm3/50 cm2) was achieved with the blend containing only amorphous DGEBA. The adhesion of the epoxy samples on concrete was greater than 6.5 MPa. The chemical resistance tests performed showed that, in general, the chemical resistance of epoxy systems decreases with increasing crystallinity content. The tighter arrangement of molecules in the crystalline regions of the epoxy matrix results in an increase in density, strength and hardness. This study presents a comprehensive examination of the crystallization of DGEBA and DGEBF, which is, as yet virtually unavailable. It also contributes to knowledge by outlining the possibility of speeding up or slowing down the crystallization process of epoxy resins, including the principle of selecting nucleating agents. [ABSTRACT FROM AUTHOR]

A method has been developed for producing an epoxy composition based on a low-viscosity epoxy-resorcinol resin, a phosphazene-containing curing agent, isophoronediamine, and thermally expanded graphite as a filler. The degree of cure and the absence of side reactions during the curing process were confirmed using IR spectroscopy. The influence of the content of phosphazene-containing curing agent and filler on the physico-mechanical properties of the composition, its fire resistance, and antistatic properties were studied. Using the UL-94 HB horizontal burning test, it was found that the addition of 10 and 20 wt. % phosphazene-containing curing agent (relative to isophoronediamine) reduces the burning speed by 10 times compared to a sample without phosphazene. The addition of a filler to a composition containing phosphazene reduces the burning speed by 25 times compared to a composition without phosphazene and imparts antistatic properties to the epoxy composition, as evidenced by the specific volume electrical resistance of the order of 101 Ohm·m. Phosphazene-containing curing agent had no statistically significant effect on specific volume electrical resistivity (p > 0.05). Tests of physico-mechanical and adhesive properties (tensile strength, compressive strength, water absorption, water solubility, abrasion resistance, and adhesive strength) of filled epoxy compositions with 10 and 20 wt. % phosphazene-containing curing agent demonstrated that these properties met the requirements for floor coverings in construction and parts of electrical devices. [ABSTRACT FROM AUTHOR]

Abstract Novel hybrid ablation thermal protection coatings (FHMP-ATPCs), employing iron trioxide ([Fe.sub.2][O.sub.3]) powder, hollow glass microspheres, and mica powder as the fillers in hydroxyl-terminated silicone oligomer-bridged epoxy resins (PSG) copolymer, [...]

Epoxy resin‐based composite materials were investigated. Samples were made of epoxy resin ED‐20 with the addition of different amounts of microspheres. Structure and sizes of small filler particles were determined. The derived compounds were tested for resistance to alternating temperatures and corrosive media. The results demonstrated that samples with the addition of 10 % of microspheres are more resistant to the impact of 25 % acid and alkali, as well as to gasoline. At the same time, the amount of the filler from 2 to 10 wt % does not influence the resistance to alternating temperatures significantly. The conducted tests demonstrated the resistance of the developed composite materials to alternating temperatures and corrosive media, which allows using them as corrosion‐resistant coatings for metal structures and in machine maintenance. [ABSTRACT FROM AUTHOR]