Curing Accelerator Research Articles

A strategy to prepare high Tg and low CTE solder resist using alkali-soluble photosensitive polyimide

Photosensitive Solder resist (SR) materials require a high glass transition temperature (Tg > 170 °C) and a coefficient of thermal expansion matching that of copper (CTE≈17 ppm/°C) to meet the demands of manufacturing processes and application reliability. However, the commonly used epoxy resin in SR materials exhibits insufficient mechanical and thermal properties, failing to meet these requirements adequately. To address this issue, alkali-soluble photosensitive poly (amic ester) (PAE) materials were synthesized. By grafting a low-temperature curing accelerator, 6-([1,1′-biphenyl]–4-yl)–4-chloroquinoline (NQL), onto the hydroxyl groups of the PAE, the resultant grafted PAE resin was blended with an alkali-soluble photosensitive modified epoxy resin (APE) to enhance the mechanical and thermal properties of the SR composite. Research indicates that due to the low-temperature curing effect and electrostatic interactions of NQL, SR-2 (with a 10 % PAE addition) exhibits a Tg of 183 °C and a CTE of 16 ppm/°C, while SR-3 (with a 30 % PAE addition) achieves a Tg of 204 °C and a CTE of 20 ppm/°C. Furthermore, with the PAE addition of 5 %, the lithography quality of SR is enhanced, enabling SR-1 to achieve a pattern resolution of up to 40 μm. The modification method involving PSPI blending has been shown to enhance the thermal stability, dimensional stability, and lithographic performance of SR, indicating significant potential applications in solder resist materials.

Acidic deep eutectic solvent as a novel catalyst for urea–formaldehyde resin curing

ABSTRACT The effect of a novel catalyst, acidic deep eutectic solvent, on the characteristics of urea–formaldehyde (UF) resins-bonded particleboard was studied in this research work. Methyltriphenyl-phosphonium bromide–protocatechuic acid (MTPPBr–PCAT) as a DES was added to the UF resin at different percentages (1%, 2%, and 3% by weight). Then, the prepared resin was used for manufacturing particleboards. Based on this research finding, DES appears to be an effective UF resin catalyst. Increasing the MTPPBr–PCAT–DES level from 0 to 3 wt% caused a decrease in pH but still within the limits acceptable to international standards requirements, and also it caused a shorter gel time and acceleration of resin curing. Wood particleboard prepared with only 1 wt% DES had higher mechanical strength and dimensional stability and lower formaldehyde emission compared to the controls bonded with UF resins catalyzed with 2 wt% NH4Cl. Under scanning electron microscopy, acidic deep eutectic solvent catalyzed UF resins-bonded panels presented a smooth and monotonous appearance. DESs as UF acidic catalysts present advantages, such as being non-toxic, being able to catalyze resin cure similarly or more effectively than the acid itself, and being recyclable as well.

Low viscosity and low temperature curing reactive POSS/epoxy hybrid resin with enhanced toughness and comprehensive thermal performance.

The mechanical and high-temperature resistance properties of epoxy resins cured at low temperatures (Tcuring ≤ 100 °C) are often inferior, and the most toughening modification methods for epoxy resins tend to compromise thermal resistance, which significantly limit the practical applications of it. Therefore, this work reported a low viscosity and low-temperature curing epoxy hybrid resin system (OPEP), adopting E-51 as a resin matrix, liquid anhydride (MHHPA) as a curing agent, tertiary amine (DMBA) as a curing accelerator, and reactive octa-epoxy terminated polyhedral oligomeric silsesquioxane (OG-POSS) as a toughening modifier. Results demonstrated that the OPEP system has excellent processability with low viscosity and long processing window period and satisfies the practical requirements of low-temperature curing. The OG-POSS exhibits superior compatibility and reactivity with the resin matrix, and its addition slightly reduces the Eα of the curing reaction and has a certain promotive effect on the curing of epoxy resin. In addition, the curing reaction rate of the OPEP resin complies with the Šesták-Berggren autocatalytic kinetics model. The impact strength, flexural strength, tensile strength, and elongation at break of the OPEP resin reached a maximum of 15.55 kJ m-2, 121.65 MPa, 90.36 MPa, and 2.48%, representing increases of 55.97%, 3.1%, 64.68%, and 26.51% compared to those of the pure resin, respectively. Notably, due to the heat-resistant inorganic silicon cage structure of OG-POSS, the thermal decomposition temperature (Td5), glass transition temperature (Tg), and heat distortion temperature (THDT) of the OPEP0.02 resin were 313.2 °C, 123.7 °C, and 102.0 °C, showing increases of 13.0 °C, 2.3 °C, and 6.8 °C compared to the pure resin, respectively, which is difficult to achieve for the general thermosetting resin toughening modification method. This research utilized organic-inorganic nanohybrid materials (POSS) to optimize the toughness and thermal stability of the resin in a coordinated manner, providing guidance for the preparation of high-performance epoxy resins that cure at low temperatures.

Valorisation of Chitosan Natural Building Block as a Primary Strategy for the Development of Sustainable Fully Bio-Based Epoxy Resins.

The non-toxic and biodegradable nature of chitosan makes it a valuable resource offering promising opportunities in the development of bio-based materials with enhanced mechanical and thermal properties. In this work, the combination of epoxidized linseed oil, oxalic or citric acids, and chitosan (CHI) as a curing accelerator presents an attractive strategy to create bio-based and sustainable thermosetting materials. This article aims to provide a comprehensive exploration of the systems reactivities, characteristics, and performance evaluation of the designed bio-thermosets. Both the nature of the two carboxylic acids and the presence of chitosan are shown to have a big impact on the thermomechanical properties of the developed networks. While oxalic acid favours the formation of elastic networks, with low Tg values (increasing with CHI content between 0.7 and 8.5 °C) and relatively low Young's modulus (~2.5 MPa), citric acid promotes the formation of very dense networks with lower mass of the segments between the crosslinks, having 20 times higher Tg values (from 36 to 45 °C) and ~161 times higher Young's modulus (from 94 MPa up to 404 MPa in these systems). The CHI has a strong impact on the curing reaction and on the overall properties, by increasing the materials' performance.

Curing Kinetics and Dielectric Properties of Anhydride Cured Epoxy Resin With Different Accelerator Contents

The addition of accelerator reduces the curing reaction temperature, changes the curing reaction process, and affects the morphology of the crosslinking structure, which would lead to the difference in the dielectric properties of the epoxy resin. In this study, the curing behaviors and dielectric properties of diglycidyl ether of bisphenol A (DGEBA)/methyl hexahydrophthalic anhydride (MHHPA) were investigated with respect to the contents of the curing accelerator, Tris-(dimethylaminomethyl) phenol (DMP-30). The curing behavior of epoxy resin was studied by differential scanning calorimetry (DSC), and it was found that the system conforms to the Sestak–Berggren kinetic model [SB ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m},{n}{)}$ </tex-math></inline-formula> ]. The accelerator content has a saturation effect on the dielectric properties of the epoxy resin curing sample, and excessive content can lead to the increase of dielectric constant and loss and decrease of breakdown strength. The cured sample with 0.5% accelerator addition has the best dielectric properties and the highest breakdown strength. The analysis concludes that the optimum accelerator content allows for a more rational curing crosslinking network.

Compositions for Limestone Restoration

Information about the lime composition used for the restoration of limestone is given. It has been shown that using a polysilicate mortar to formulate a lime composition contributes to an increase in water resistance, adhesion strength of the composition to the base, and acceleration of curing. A primer composition is proposed, including liquid sodium glass and calcium chloride.

Molecular dynamics simulation of crosslinking process and mechanical properties of epoxy under the accelerator

AbstractTo simulate the crosslinking process of epoxy resin under the accelerator action, the crosslinking system of bisphenol‐A diglycidyl ether (DGEBA) as a monomer, methyl tetrahydro‐phthalic anhydride (MTHPA) as a thermal curing agent and 2,4,6‐tris (dimethylaminomethyl) phenol (DMP‐30) as a thermal curing accelerator has been studied using molecular dynamics (MD) simulation. An algorithm that can construct the high‐crosslinked system with different crosslinking density is completed based on the Perl language, and the subsequent properties are simulated. The results of molecular dynamics simulation show that modulus have an increasing trend, and glass transition temperature (Tg) raises from 325 K to 480 K when crosslinking density is from 0% to 95.5%. Conversely, cohesive energy density lessens from 620 J/cm3 to 170 J/cm3, solubility and Poisson's ratio decrease, and the tensile strength firstly increases and then diminishes. The friction coefficient decreases firstly and then increases, meanwhile, the temperature suddenly adds by 20 K and the relative concentration distribution (RCD) grows by 1.58 times at the contact surface. This study predicts for the crosslinking process and micro mechanical properties in the DGEBA/MTHPA/DMP‐30 system.

Experimental Analysis on the Curing and Adhesive Behaviour of Standard Moisture-cured and Fast-cured Polyurethanes Used in Automotive Industry

In this paper, the adhesive behaviour of different polyurethane glues was studied and compared. The study was inspired by real conditions in the production of car windows, and it is divided into several parts, which deal with three types of polyurethane adhesives. The first type is a standard one-component polyurethane adhesive, which cures with air humidity. The second type is a one-component polyurethane adhesive with the addition of a curing accelerator. And the third type is a two-component polyurethane adhesive. Adhesive blocks of defined dimensions and plastic parts glued to the glass were used for this experiment to simulate a real product. The influence of temperature and humidity on the curing process was evaluated. The test included measuring the force required to tear the parts from the glass and assessing the type of failure. Based on the achieved results, the adhesives were evaluated regarding their applicability in the real automotive industry and the key properties necessary to maintain the safety and quality of the glued part were determined

Novel High-Temperature-Resistant Phosphates: Thermal Ablation Behavior of La-Al System Phosphates at 2000 °C.

The saturation-free and directionless cross-linking and interpenetration processes between La3+ and [(H2PO4)2Al(HPO4)]-plasma in La–Al phosphate by mixing Al(OH)3, CrO3, and H2O2 dissolved in H3PO4 and La2O3 as a curing accelerator, as well as the thermal stability of the La–Al phosphate bulk materials and the evolutions of the phase composition and morphology at different temperatures were studied using thermogravimetric/differential scanning calorimetry under different temperatures in a muffle furnace. The La–Al phosphates showed good thermal stability, and the thermal weight loss rate of the materials decreased from 18% before heat treatment to ∼2% after heat treatment. In addition, the La–Al phosphate bulk material showed excellent resistance to ablation when subjected to ablation by an oxyacetylene flame at 2000 °C for 30 s. It evolved into a dense LaPO4 and AlPO4 high-temperature phase layer on the sample surface, which prevented further ablation damage to the sample and significantly improved the temperature resistance of the La–Al phosphate bulk material.

Thermally Controlled Acceleration of Epoxy Resin Curing through Polymer-Bound Imidazole Derivatives with High Latency

Imidazole-containing polymeric accelerators were synthesized through free-radical polymerization and applied in the curing of diglycidyl ether of bisphenol A resin with the hardener dicyandiamide. Reactivity and storage stability were followed via differential scanning calorimetry, and an increased pot life was observed after incorporation into polymers. Depending on the employed monomers and composition, the compatibility with epoxy resin was adjusted and the storage stability thereby improved, while a high reactivity is retained under curing conditions. Microscopy imaging showed the dissolution of the polymeric accelerators in epoxy resin above a critical temperature enabling a high reactivity. The best performing accelerator was then applied in an epoxy adhesive film formulation. The strength of the bonding of stainless-steel test bodies was examined in a lap shear test showing superior long-term stability while maintaining efficient acceleration of this type of polymeric accelerator for adhesive applications.

Imidazole derivative with an intramolecular hydrogen bond as thermal latent curing accelerator for epoxy/phenolic resins

AbstractOne‐component epoxy systems with long shelf life during storage or transportation, while high curing reactivity during molding as well as satisfactory mechanical and thermal performances after curing, are extremely essential for industrial application. Herein, we used salicylaldehyde and o‐phenylenediamine to synthesize 2‐(2′‐hydroxyphenyl)‐1H‐benzimidazole (HPBI), an imidazole derivative with an intramolecular hydrogen bond between the phenolic hydroxyl group and the pyridine‐type nitrogen atom of imidazole ring, and further employed HPBI as a thermal latent curing accelerator for epoxy/phenolic resins. The intramolecular hydrogen bond endowed HPBI with inert activity toward resins at room temperature, making the one‐component resin system a long‐term storage stability (21 days of shelf life at 30°C). Once rising the temperature to a high degree, a rather high activity of HPBI to accelerate the curing process of epoxy/phenolic resins. It was attributed to the effective release of high activity of the pyridine‐type nitrogen by breaking the intramolecular hydrogen bond at high temperature. In addition, the resulted thermosets from HPBI also possessed the comparable Tg (&gt;130°C, determined by DMA) and thermostability (Td‐5% &gt; 380°C) with that from common curing accelerators. Therefore, HPBI was proved to be a promising thermal latent curing accelerator applied in electronic packaging field.

Triphenylphosphine‐containing microcapsules fabricated from Pickering emulsions as a thermal latent curing accelerator for an epoxy/anhydride system

AbstractLatent curing accelerators are essential for application to one‐component epoxy systems in various industries, such as coatings, adhesives and electronic packaging. Herein, we developed organic–inorganic hybrid microcapsules encapsulating triphenylphosphine (TPP) by Pickering emulsion polymerization of styrene and methoxyethyl methacrylate with dimethoxydiphenylsilane‐modified silica nanoparticles as emulsifiers. The microcapsules were further surface‐modified by epoxy silane and employed as a thermal latent curing accelerator for an epoxy/anhydride system. Good dispersibility and interfacial bonding of the hybrid microcapsules with the resin matrix were observed. Compared with TPP, the microcapsule‐type accelerator endowed the one‐component epoxy curing system with significantly enhanced storage stability at room temperature of 25 °C (a pot life of 20 days) and a comparable curing activity at high temperature. The activity of the encapsulated accelerator can be blocked and released rapidly and effectively with increasing temperature to trigger the segmental motion of the polymeric microcapsules. Furthermore, the addition of microcapsules increased the glass transition temperature and thermal stability of the epoxy thermosets owing to the organic–inorganic hybrid character. Moreover, the toughness of the cured resin was also improved. Therefore, the latent curing accelerator demonstrated a promising prospect for application in high‐performance one‐pot epoxy formulations. © 2021 Society of Industrial Chemistry.

Development of the Tetrabutylphosphonium Carboxylates as Latent Curing Accelerators for Thermosetting System of Epoxy Resins and Bismaleimide Resins

Development of the Tetrabutylphosphonium Carboxylates as Latent Curing Accelerators for Thermosetting System of Epoxy Resins and Bismaleimide Resins

UV硬化促進・機能付与剤 「DPNG」・「IPEMA」

UV硬化促進・機能付与剤 「DPNG」・「IPEMA」

Regression rate of paraffin-based fuels in hybrid rocket motor

Paraffin-based fuels are regarded as a promising solid fuel for hybrid rocket motor (HRM) owing to high regression rate, excellent mechanical performance, and high dropping point. The regression rate of paraffin-based fuels was characterized by static fire test with nitrous oxide (N2O) and gaseous oxygen (GOX) as oxidizer, and the effect of combustion catalyst, injector and chamber pressure on the regression rate was evaluated in this study. The results show that the average regression rates of paraffin-based fuel with GOX and N2O are similar under the optimal oxidizer/fuel (O/F) ratio, and the exponent n is larger with GOX as the oxidizer, indicating high sensibility to oxidizer mass flux. The average regression rate increased with the increase in swirling number Sg, and the tangential injector with Sg of 6.83 improved the regression rate significantly. The local regression rate unchanged with axial position when a jet injector was used, but a complex local regression rate appeared at the first half of fuel grain for tangential injector. Both copper chromite and cobalt stearate obviously increased the regression rate; however, only copper chromite could be used as a preferable regression rate improver owing to significant curing acceleration of fuels by cobalt stearate. The average regression rate slightly increased with the increase in chamber pressure with GOX as the oxidizer, but a noticeable positive relationship could be found for the cases of N2O.

Synthesis of isocyanurate‐based imidazole carboxylate as thermal latent curing accelerator for thermosetting epoxy resins

AbstractA novel thermal latent curing accelerator, 1‐(2‐cyanoethyl)‐2‐methylimidazole/tris (2‐carboxyethyl) isocyanurate adduct (2MICN‐T), was successfully synthesized through an acid–base neutralization of tris(2‐carboxyethyl)isocyanurate (TCEIC) and 1‐(2‐cyanoethyl)‐2‐methylimidazole (2MICN). It was further added into diglycidylether of bisphenol A based epoxy resin/methylhexahydrophthalic anhydride mixture to form one‐component curing systems. With the addition of 2 wt% of 2MICN‐T, the one‐component system could be steadily stored for more than 1 month at room temperature, while the shelf life of 2MICN curing system was only 2 days. Nonisothermal differential scanning calorimeter also demonstrated the excellent thermal latency of 2MICN‐T in low‐temperature region and rapid initiation of the curing reaction when raising temperature. Compared to the cured resins with original 2MICN as accelerator, the resulted thermosets exhibited enhanced glassy storage modulus, glass transition temperature, and thermal stability when 2 wt% of 2MICN‐T was applied. It was attributed to the chemical incorporation of the isocyanurate moieties with multi carboxyl groups and nitrogen‐contained heterocyclic ring, effectively increasing the crosslinking density, chain rigidity, and heat resistance of the cured resin. Thus, it is suggested that 2MICN‐T can play both roles as latent curing accelerator and modifier for one‐component epoxy compounds, and is particularly recommended for application in electronic packaging fields.

ВЛИЯНИЕ МОДИФИКАТОРОВ НА ВРЕМЯ ОТВЕРЖДЕНИЯ ФЕНОЛОФОРМАЛЬДЕГИДНОГО СВЯЗУЮЩЕГО ДЛЯ ПРЕССОВАНИЯ ФАНЕРЫ ПРИ НИЗКОТЕМПЕРАТУРНОМ РЕЖИМЕ

Volumes of plywood production with increased water resistance for indoor and outdoor use (FSF brand) are increasing in Russia. The demand for it in the country and in the world continues to grow. The phenol-formaldehyde oligomer during the curing process passes through the stages of resol, resitol and resite. Ensuring long-term water resistance of plywood is possible only if the resite stage is reached and the solidified phenol-formaldehyde resin (FFR) reaches non-melting and insoluble state. The problem is that the industrial process of FSF plywood pressing is carried out in the rezitol temperature range. In literature, there are conflicting data on the temperature ranges of the stages of the FSF polycondensation process. The authors have proposed to operate with scientific data on the temperature ranges of FFR curing, confirmed by the results of spectroscopic studies. It is necessary to develop phenol-formaldehyde binder compositions capable of curing to the resite stage at lower pressing temperatures than unmodified FSF to ensure the necessary operational characteristics of FSF plywood. In this study, a number of modifiers have been proposed that potentially reduce the time it takes to press plywood at low temperatures. The gelatinization time of the phenol-formaldehyde binder based on the SFZh-3014 resin (according to 20907-2016 State Standard) and modifying additives (hydrogen peroxide, eight-water zinc sulfate, ammonium alum, anhydrous magnesium chloride, six-water iron chloride, six-water aluminum chloride, aluminum dimethyl sulfate, dimethyl glyoximate, and sulfate, sulfosalicylic two-water acid) have been determined. A study of the gelatinization process in the presence of a large number of modifying additives (more than 1.5%) revealed a significant deterioration in the spreadability of the binder. Therefore, it is recommended to use FFR curing accelerators in the amount not exceeding 1-1.5%.

Comprehensive properties study of low-temperature imidized polyimide with curing accelerators

Six curing accelerators of QL, IQL, 2-QL, 4-QL, 8-QL, and THQL were incorporated with PAA for low-temperature imidization. The results proved that the acidity and molecular structure possess significant effect on the properties of polyimides.

Effect of press temperature on some properties of cement bonded particleboard

It is known that there is a correlation between hydration heat and physico-mechanical properties of wood based cement panels. Cement hydration is affected by many variables, such as chemical composition, water/cement ratio, wood/cement ratio, wood chemical properties, mineral additions and producing conditions. This study mainly aimed to investigate the effects of press temperature on some properties of three-layer cement bonded particleboard made from the particles of spruce (Picea orientalis) and poplar (Populus tremula). For this purpose, a total of 16 experimental board groups with 1200 kg/m3 target density and 1/3 wood-cement ratio were produced at the press temperatures of (20, 30, 40, 50, 60, 70 and 80) °C. As cement curing accelerator, CaCl2 was used at a rate of 5 % (cement weight basis). The physical, mechanical and thermal properties of the boards were determined. The results indicated that the press temperature substantially affected the properties of cement-bonded particleboard depending on the wood species. In the light of this study, the optimum temperatures in producing of cement-bonded particleboard were found as 40 °C for poplar wood and 60 °C for spruce wood.

Microcapsules derived from Pickering emulsions as thermal latent curing accelerator for epoxy resins

Organic-inorganic hybrid microcapsules encapsulating 2-phenylimidazole (2-PhIm) were prepared by Pickering emulsion polymerization of styrene and divinyl benzene using methacryloyloxy silane-modified silica particles as the stabilizer, and served as a thermal latent curing accelerator for diglycidylether of bisphenol A epoxy/anhydride system. The one-component curing composition containing 5wt% of the microcapsules exhibited an excellent storage stability. The pot life at room temperature was as long as 30 days, while which of 2-PhIm curing system was only 2 days. At elevated temperature, the encapsulated 2-PhIm could be released from microcapsules effectively, and instantly accelerated the curing reaction. Meanwhile, the addition of microcapsules did not cause an adverse effect on the thermomechanical performance of the epoxy thermosets. In addition, the latency and curing behavior could be facilely regulated at a wide range of temperature by adjusting monomer ratios of the polymer matrix, to match different process temperatures. The microcapsules with robust cross-linked polystyrene matrix structure also showed good resistance to shearing forces, indicating their feasibility for high-speed mixing or kneading process in practical applications. It is suggested that the novel latent curing accelerator is potential for high-performance one-pot epoxy formulations, particularly recommended for application in electronic packaging fields.