Curing Accelerator Research Articles

Effects of Chemical Composition of Ca(OH)2 and Precursors on the Properties of Fast-Curing Geopolymers

Geopolymer is an alumina silicate-based ceramic material that has good heat-resistance and fire-resistance; it can be cured at room temperature, and thus its manufacturing process is simple. Geopolymer can be used as a reinforcement or floor finish for high-speed curing applications. In this manuscript, we investigate a high-speed curing geopolymer achieved by adding calcium to augment the curing rate. Metakaolin is used as the main raw material, and aqueous solutions of KOH and K2SiO3 are used as the activators. As a result of optimizing the high bending strength as a target factor for geopolymers with SiO2 / Al2O3 ratio of 4.1 ~ 4.8, the optimum ranges of the active agent are found to be 0.1 ≤ K2O / SiO2 ≤ 0.4 and 10 ≤ H2O / K2O ≤ 32.5, and the optimum range of the curing accelerator is found to be 0.82 ≦ Ca (OH)2 / Al2O3 ≦ 2.87. The maximum flexural strength is found to be 1.35 MPa at Ca (OH)2 / Al2O3 = 2.82, K2O / SiO2 = 0.3, and H2O / K2O = 11.3. The physical and thermal properties are analyzed to validate the applicability of these materials as industrial insulating parts or repairing·finishing materials in construction.

Green fabrication of graphene oxide/epoxy nanocomposite and its application in diamond abrasive tools

In order to improve the wear resistance and service life of the epoxy resin (EP)-bonded diamond abrasive tools, graphene oxide (GO) was incorporated through a green method without any organic solvents. A curing accelerator, 3-methyl-N,N-diethylbenzenamine (3-MBDEA) acts as a phase transfer agent which rapidly catches GO from water phase to epoxy phase, and the diamond/GO/EP abrasive tools were fabricated via in situ polymerization. The effect of GO on the structure of EP was characterized, and the grinding performances of as-prepared diamond/GO/EP abrasive tools were evaluated in the grinding of concrete. Results show that the service life of the diamond/GO/EP abrasive tools are significantly improved by the incorporation of GO. In the case of the diamond with the size of 50 μm (D50)/GO0.5/EP abrasive tool only with 0.5 wt% GO, its service life increases by 75% compares to that of the D50/EP abrasive tool. The excellent performance of diamond/GO/EP abrasive tools is attributed to the improvement of the wear resistance of EP and the enhancement of the interfacial adhesion between EP and diamond with the addition of GO. This work may provide a potential industrial application for graphene-related materials.

Energy Efficient Polystyrene Aerated Concrete Composite Products and Condition Monitoring for Building Structures and Facilities in the Arctic Regions

The harsh climatic conditions of the Arctic zone of the Russian Federation in combination with the current requirements for ensuring comfortable accommodation conditions in buildings and structures lead to strengthening of respective thermal protection regulations. The article outlines the basics for the multi-layer composite material technology based on the use of aerated concrete and polystyrene foam. The novelty of the technology, as confirmed by respective patents of the Russian Federation, consists in layering of aerated concrete and non-foamed or partially foamed polystyrene into a mold, followed by its closing with a lid and subsequent heat and moisture treatment by steaming. The steaming process triggers spontaneous expansion of the aerated concrete mixture and polystyrene, compaction of their structural layers, and acceleration of concrete curing. The result is a composite product with improved performance, complying with the current regulatory requirements for the thermal protection of buildings.In order to ensure the reliability and durability of construction projects, systematic quality control is required for all raw materials used in manufacturing of building structures, as well as proper condition monitoring for all operated buildings and structures. The Kola Testing Centre for Building Materials and Articles (KTCBMA), established 20 years ago, conducts certification and definitive testing of building materials for compliance with the current standards, as well as non-destructive testing of concrete and reinforced concrete structures.

Acceleration of epoxy resin curing by using a combination of aliphatic and aromatic amines

Curing of epoxy resins with aromatic amines, which provides an excellent combination of physical and mechanical properties, requires high temperatures. In this research, the amidoamine adduct of tall oil with triethylenetetramine have been used for acceleration of the reaction of the aromatic amine (diaminodiphenyl sulfone, DDS) with the diglycidyl ether of bisphenol A (DGEBA) epoxy resin. The kinetics of the curing reaction of DGEBA with a mixture of two hardeners was investigated by the non-isothermal DSC method. It was shown that the activation energy of curing decreased from ~ 68 to ~ 59 kJ/mole at amidoamine introduction. Nevertheless, there were no new bands in the IR-spectra of the cured epoxy resins. The acceleration of the curing reaction of the aromatic amine was apparently due to the autocatalytic action of the hydroxyl groups formed by the reaction of the epoxy resin with the amidoamine. Besides acceleration of curing, use of the hardener mixture significantly increased the rubbery-plateau modulus, while not influencing on the value of the elasticity modulus of the cured resin in the glassy state. A disadvantage of using amidoamine for accelerating the curing was lowering of the glass transition temperature of the cured polymer.

Structure and protective properties of epoxy-polyester powder coatings containing curing accelerator

As a result of the study, the effect of curing accelerators (heterocyclic amine and zinc-containing accelerator) on the structure, physico-mechanical and protective properties of coatings based on powder epoxy-polyester compositions was established. The introduction of accelerators into the compositions affects the depth and speed of the curing process of film formers and provides the possibility to reduce the curing temperature. It has been established that the use of heterocyclic amine accelerator is more effective than a zinc-containing catalyst. For compositions containing heterocyclic amine, a decrease in gel time and an increase in the complex of physico-mechanical and protective characteristics of the coatings are observed, which were evaluated for the resistance of the coatings to the static action of a 3 % solution of sodium chloride. It is shown that changes in the protective properties of coatings, depending on the composition, correlate with the structural parameters of the polymer film and are due to the formation of the spatial structure of the polymer with different cross-link density. The use of mixtures of the investigated curing accelerators leads to an increase in the density of the polymer spatial network. This provides high protective properties of coatings to the action of aggressive electrolytes by reducing the permeability of corrosive media into the coating material. For 5000 hours of testing there are no pockets of corrosion under a film and no significant disruption of the continuity of the coatings (bubbles, peeling, wrinkling and cracking) in comparison with the basic compositions that do not contain accelerators.

The Effect of the Thermal Mechanical Properties of Nonconductive Films on the Thermal Cycle Reliability of 40-<inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>m Fine Pitch Cu-Pillar/Ni/SnAg Microbump Flip-Chip Assembly

Nonconductive films (NCFs) have been introduced for 3-D through-silicon via chip stacking interconnection using reliable fine pitch Cu-pillar/Ni/SnAg microbumps. In this paper, four NCF materials with various elastic modulus and coefficient of thermal expansion (CTE) values were used to investigate the effect of the thermomechanical properties of the NCFs on the thermal cycle reliability of fine pitch Cu-pillar/Ni/SnAg/Cu-pad interconnections. The NCFs’ materials properties were adjusted by changing the ratio of epoxy resins and the curing accelerators. Compared with the borate curing accelerator, the use of the imidazole curing accelerator resulted in better thermomechanical properties on NCFs. And, NCFs containing higher ratio of solid epoxy resins showed higher elastic modulus and higher Tg values when using imidazole curing accelerator. After thermocompression bonding using four different types of NCFs, a thermal cycle reliability test (−40 °C–125 °C) was performed to investigate the effects of the NCFs’ thermomechanical properties on the reliability of Cu-pillar/Ni/SnAg/Cu-pad joints. Due to the CTE mismatch of chips and printed circuit board (PCB) substrates, the SnAg solder joint interconnections were damaged during the thermal cycling. Compared with the four types of NCFs, NCFs with higher elastic modulus at 30 °C showed better thermal cycle reliability. And among the NCFs with similar CTE values, those with higher Tg and higher elastic modulus at 30 °C value showed better thermal cycle reliability. In summary, the NCFs with lower CTE and higher elastic modulus at 30 °C were suitable for highly thermal cycle reliable Cu-pillar/Ni/SnAg/Cu-pad bump joints.

Curing properties of high‐Ortho phenol‐formaldehyde resins with co‐catalysis

ABSTRACTIn this study, sodium carbonate (Na2CO3) was used as a catalyst to prepare high‐ortho phenol‐formaldehyde (HOPF) resin, and ester and carbonate curing accelerators were used to increase its curing rate. The physicochemical properties of the prepared resins and the mechanism of curing acceleration were investigated. The results showed that, with the addition of Na2CO3, the ortho/para ratio of methylol groups increased from 7.257 to 27.800. The gel time of the cure‐accelerated HOPF resins decreased from 620 to 240 s as compared with PF resin. The bonding strength of plywood bonded with the cure‐accelerated HOPF resins were all above 0.70 MPa. The curing acceleration was caused by the carbonate ions rather than the metal ions, and a temporary incorporation mechanism apparently occurred for the ester accelerators. The prepared phenolic resin had fast curing rate, low curing temperature, high thermal stability, and favorable mechanical performance, which has potential for industry applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47229.

Methylpiperidine-functionalized graphene oxide for efficient curing acceleration and gas barrier of polymer nanocomposites

We synthesized methylpiperidine-functionalized graphene oxide (MP-GO) by introducing 4-amino-1-methylpiperidine into reactive epoxy and/or carboxylic acid groups on pristine GO. Then, we applied the MP-GO as a curing catalyst for polyimide (PI) nanocomposites. The MP-GO was found to be an effective base-catalysts for the thermal conversion of polyamic acid (PAA) precursor to PI. Interestingly, when 3 wt% of MP-GO was added to the PI matrix, the complete imidization of nanocomposites was achieved at a temperature lower than 200 °C. In addition, the PI/MP-GO nanocomposite films exhibited reinforcement of the oxygen barrier properties which were even better than those of pristine PI, due to the excellent dispersion state of MP-GO and the favorable non-covalent interaction between MP-GO and the PI matrix. Comparison to pristine PI, the oxygen permeability of nanocomposite films that contained only 1 wt% of MP-GO loading was significantly decreased, by about 80%. Furthermore, all the PI/MP-GO nanocomposites exhibited high thermal stability.

Usability of chemical additives to accelerate initial curing time of AAC

AbstractAutoclaved aerated concrete (AAC) products have been promising materials for the construction sector. For this reason, fast production techniques are becoming more important in this area. In the present study, effects of chemical accelerators on the initial curing time of AAC blocks have been studied. Two different organic additives (Ad1 and Ad2), which are commercial chemical agents used as setting accelerators in cement sector, were studied to investigate effects of curing times of G2/350 receipt. Ad1 and Ad2 were added into the raw materials mix of G2/350 recipe in proportion of 0.3, 0.6, and 0.9% of cement amount in raw materials mix during mixing process. Curing times of expended mud (cake) samples were measured by the hardening apparatus. On the other hand, mechanical, physical, and microstructural analyses of autoclaved samples were investigated. According to the results, it is determined that Ad1 and Ad2 can be used as a curing accelerator in production of AAC blocks. In addition to that Ad1 (in the amount of 0.3%) is the most suitable chemical agent to shorten initial curing time of R1 recipe of AAC.

The synthesis of a new ionic liquid and its use as a multifunctional additive in different rubber composites

A novel functional ionic liquid (ILM) was synthesized using the ion exchange reaction of mercaptobenzothiazole (MBT) and 1-allyl-3-methylimidazolium. ILM was then added into carbon black/rubber, silica/rubber and microcrystalline cellulose (MCC)/rubber compounds, respectively, and its effects on the processing, physico-mechanical, and dynamic properties of the vulcanizates were investigated. For carbon black/rubber and silica/rubber compounds, ILM worked very well as a curing accelerator and surface modifier of carbon black and silica. For MCC/rubber compounds, the improvement was slight for the curing rate but obvious for the tensile properties. And it is noteworthy that the sizes of the MCC were decreased in situ from 20–90 μm to less than 5 μm during the processing of the rubber compounds, and the interfacial bonds between MCC and the rubber matrix were also improved. These results indicate that ILM is a multifunctional additive that can be used in different rubber composites.

Preparation and properties of novel fluorinated epoxy resins cured with 4-trifluoromethyl phenylbenzimidazole for application in electronic materials

A novel 3-trifluoromethyl phenylhydroquinone epoxy monomer (3-TFMEP) and a novel 4-trifluoromethyl phenylbenzimidazole (4-TFMBI) curing agent both with trifluoromethyl moieties were synthesized via a multi-step procedure. Their chemical structures were confirmed by FT-IR and 1H NMR spectra. Herein, we employed 3-TFMEP as the epoxy matrix, and 4-TFMBI as the curing agent or the curing accelerator. Next, we prepared a series of epoxy resins with four kinds of different curing system as 3-TFMEP/Methylhexahydrophthalicanhydride(Mehhpa)/2-methylimidazole (2-MI), 3-TFMEP/Mehhpa/4-TFMBI, 3-TFMEP/2-MI and 3-TFMEP/4-TFMBI in order to investigate the variation of the properties with different curing agents and curing accelerators. The result showed that no matter whether 4-TFMBI was used as the curing agent or as the curing accelerator, the epoxy resin cured with 4-TFMBI exhibited high mechanical and thermal stabilities, as well as low dielectric constant and dielectric loss. In particular, 3-TFMEP/4-TFMBI possessed the highest Td5% (the decomposition temperature of 5% weight loss) of 374 °C, 131 °C higher than 3-TFMEP/Mehhpa/2-MI. Additionally, the storage modulus of 3-TFMEP/Mehhpa/4-TFMBI was 3266 MPa at 25 °C, which was much higher than other kinds of cured epoxy resins. Moreover, 3-TFMEP/4-TFMBI possessed the lowest dielectric constant of 3.38 at 107 Hz among these cured epoxy resins. Therefore, we believed that this novel fluorinated epoxy resin cured with 4-TFMBI containing 3-trifluoromethyl moieties have a great potential for application in the electronic packaging material field.

Enhancing the processibility of high temperature polymerizing cardanol derived benzoxazines using eco-friendly curing accelerators

The advent of bio-based benzoxazine in the field of polybenzoxazines is a major breakthrough towards their sustainable development. Cardanol derived benzoxazine offers solvent less synthesis and processing benefits over the petro based resin, however these mandate high curing temperatures. The polymerization temperature can be alleviated through structural modifications or physical blending with curing accelerators; the latter approach being preferred in view of its economic viability. Most of the curing accelerators are moisture sensitive, which adversely affect the end performance of the polymer. In this paper, the potential of eco-friendly stearates based on transition metals as curing accelerators for the polymerization of cardanol based benzoxazine resin has been demonstrated. Metal stearates were formulated with bio-based monomer which leads to significant lowering of the curing profiles, the extent of which was proportional to the amount of accelerator. The hydrophobicity associated with the long alkyl chain in stearate bestows it hydrolytic stability, which allows its use under ambient conditions without special caution. Zinc(II) stearate exhibit highest activity towards acceleration and its inclusion does not alter the viscosity of the formulation offering a processing advantage. Kinetic parameters associated with polymerization of the resin were established using Kissinger Akahira Sunose method.

Epoxidized soybean oil cured with tannic acid for fully bio-based epoxy resin.

The construction of fully bio-based epoxy resins (EP) has been of particular interest in both academia and industrial circles for years; among these, epoxidized soybean oil (ESO) derived thermosets have received the most attention, but they usually exhibit poor performance due to their flexible fatty chains. Herein, tannic acid (TA), with its great degree of functionality and massive aromatic structures, was chosen as the multi-phenol curing agent for ESO to prepare fully bio-based EP thermosets with a high relaxation temperature and satisfactory mechanical properties. As a natural 2-substituted imidazole-containing substance, histidine (H) was used as the curing accelerator under moderate curing conditions (120–180 °C). This EP system showed high curing activity and a good curing degree while operating. The cured thermosets were found to be thermally stable (T5% > 270 °C) and displayed a high relaxation temperature (77 °C) with a tensile strength of 23 MPa. Preliminary adhesion tests showed that the cured product exhibited a high lap-shear strength of about 19 MPa in adhesion failure mode. Taking these advantages into account, this kind of fully bio-based EP could introduce more chances for versatile applications, such as being used in structural materials and construction adhesives.

Biobased Heat Resistant Epoxy Resin with Extremely High Biomass Content from 2,5-Furandicarboxylic Acid and Eugenol

Preparing a biobased (biomass-based) high performance epoxy resin with extremely large biomass content is of great importance for sustainable development. Herein, a new epoxy resin with a precise structure, bis(2-methoxy-4-(oxiran-2-ylmethyl)phenyl)furan-2,5-dicarboxylate (EUFU-EP), was synthesized from two biobased green and low toxic compounds (2,5-furandicarboxylic acid and eugenol) and the biomass content of EUFU-EP is as large as 93.3%. In addition, a new biobased epoxy resin, EUFU-EP/MHHPA, was prepared by using methyl hexahydrophthalic anhydride (MHHPA) as the curing agent and 2-ethyl-4-methylimidazole as the curing accelerator. The curing reactivity and integrated performances including thermal and mechanical properties as well as flame retardancy of the cured resin were systematically researched and compared with those of petrochemical resource-based epoxy resin (DGEBA/MHHPA) consisting of commercial diglycidyl ether of bisphenol A (DGEBA), MHHPA and 2-ethyl-4-methylimidazole. Results show that E...

Ionic liquids as curing catalysts for epoxide-containing compositions

Studies of the chemical structure of ionic liquids and its influence on the curing regularities and the properties of epoxide-containing liner compositions and the epoxy binder were performed. The used ionic liquids were compounds in which imidazolium and pyrrolidinium cations correspond to dicyanamide and tetracyano-borate anions. It was shown that ionic liquids with a dicyanamide anion possess a catalytic activity that is expressed in acceleration of curing of the epoxy-rubber liner composition, the EDT-10 epoxy binder, and the microorganoplastic on its basis. It was established that the use of ionic liquids as a curing catalyst instead of dimethylbenzylamine does not affect physical and mechanical characteristics, such as lifetime, strength, swelling in transformer oil, and structural glass-transition temperature of the liner composition and provides a high stable strength of microorganoplastic.

The preparation of multifunctional accelerators derived from tea phenols and their use in rubber compounds

Tea polyphenols (TPs) are natural compounds extracted from tea trees whose molecular structures possess many phenolic hydroxyl groups, and therefore are highly reactive. Based on the principle of the Mannich reaction, two types of multifunctional accelerators (Tea polyphenols-mercaptobenzothiazole [TPM] and Tea polyphenols-N-tert-butylbenzothiazole-2-sulphenamide [TPN]) were synthesized by the reaction of TPs with 2-mercaptobenzothiazole and N-tert-butylbenzothiazole-2-sulphenamide, respectively. The chemical structures of TPM and TPN were characterized using Fourier transform infrared spectroscopy, and the curing activity was measured using a vulcameter. The results showed that TPM and TPN had been synthesized successfully and possessed curing activity similar to that of traditional accelerators. TPM and TPN were then used in silica/rubber compounds to determine their effects on processing and on physiomechanical and antiaging properties. The results showed that TPM and TPN improved the curing rate of silica compounds and also improved the dispersion of silica in a rubber matrix as observed using transmission electron microscopy. Furthermore, the retention of tensile strength was higher for TPM and TPN vulcanizates after air aging than it was for the control sample. These results indicated that TPM and TPN, which incorporated the functions of a “curing accelerator,” a “silica surface modifier,” and an “antidegradant,” were new multifunctional accelerators for silica/rubber compounds.

ZnO Nanoparticles Bonded to SiO2 Filler as a Curing Accelerator in Cold Vulcanizing Adhesives

6th International Congress and Exhibition on Advances in Applied Physics and Materials Science (APMAS) -- JUN 01-03, 2016 -- Istanbul, TURKEY

A Simplified Model to Describe the Effect of Alkyl Anilines on the Polymerization of Methyl Methacrylate

SummaryIn the formulation of acrylic coatings, monomer blends are required to cure in situ using a peroxide initiator. Curing accelerators (typically alkyl anilines) are added to the blend in order to initiate the curing process at room temperature. This was proved to cause a process safety issue related to the presence of accelerators that increase the possibility of runaway reactions especially at industrial scale. In this paper, the polymerization of methyl methacrylate containing different curing accelerators has been studied. Based on Differential Scanning Calorimetry tests, a simplified kinetic model for the polymerization process has been developed, describing the induction time due to the presence of stabilizers, the global kinetic rate, and the influence of diffusion phenomena, based on a free volume theory approach specifically modified for the free radical polymerization of methyl methacrylate added with different types of accelerators.

Influence of curing accelerators on the imidization of polyamic acids and properties of polyimide films

In order to lower the imidization temperature of polyamic acids (PAA), the catalytic activities of the curing agents p-hydroxybenzoic acid (PHA), quinoline (QL), benzimidazole (BI), benzotriazole (BTA), triethylamine (Et3N) and 1, 8-diazabicyclo [5.4.0]undec-7-ene (DBU) were investigated in the process of thermal imidization of PAA. In addition, the effect of these various curing agents on the thermal stabilities and mechanical properties of the resultant polyimide (PI) films was determined. Quinoline was found to be an effective curing accelerator in the use of two-step method for synthesizing PI. Due to its moderate base strength, low steric crowding effect and moderate boiling point, quinoline could not only accelerate PAA to achieve imidization completely at 180 °C, but also maintain the mechanical properties and thermal stability of the ordinary PI film. Any residual quinoline could be removed from PI films by heating at 250 °C for 4 h.

Metal‐Organic Frameworks as curing accelerators for benzoxazines

AbstractBenzoxazine resins, although exhibiting attractive properties; particularly high thermal stability and near zero‐ shrinkage, suffer from a major drawback associated with its high curing temperature. In view of the Lewis acidity associated with the Zn4O nodes in a zinc based metal organic framework [Zn4O(BDC)3, MOF5], we considered it of interest to explore its potential as a curing accelerator for a representative biobased benzoxazine resin. MOF 5 was solvothermally synthesized and characterized using different techniques including powder X‐ray diffraction (PXRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Fourier transform infrared spectroscopy (FT‐IR) and Nitrogen physisorption measurements. Bio‐based benzoxazine resin was synthesized by mannich type condensation of cardanol and aniline with formaldehyde under solventless conditions, the structure of which was confirmed using FT‐IR and 1H‐NMR. The curing behavior of the synthesized resin was systematically investigated using non‐isothermal Differential Scanning Calorimetry (DSC). Introduction of MOF 5 led to a shift in the curing profile to lower temperature, the extent of which was proportional to the amount of MOF 5 in the formulation. DSC studies were performed at different heating rates to establish the kinetic parameters associated with the curing of the resin. Activation energy, as calculated using Kissinger Akahira Sunose method, was found to concomitantly decrease from 98 kJ/mol to 58 kJ/mol upon addition of MOF 5 (5 % w/w).