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Vinyl‐substituted hydridopolycarbosilane (VHPCS) is widely studied for its low viscosity, abundance of active functional groups, rapid curing, and high ceramic yield. The curing reactions mainly involve the free radical polymerization of vinyl and hydrosilylation reactions, but these reactions typically require high temperatures such as 160–250°C. The curing behavior of VHPCS‐17 with a tert‐butyl peroxybenzoate/Nickel acetylacetonate (TBPB/NIAA) system is investigated using differential scanning calorimetry and in situ Fourier transform infrared. The properties of VHPCS‐17 with different initiator systems and VHPCS with different vinyl contents (under TBPB/NIAA system) are studied using thermogravimetric analysis and x‐ray diffraction. The results demonstrate that the TBPB/NIAA system can facilitate the free radical polymerization of vinyl; moreover, this system decreases the peak temperature of the curing reaction from 251 to 141°C and increases the ceramic yield from 80.49% to 89.88%. The ceramic yield of cured VHPCS increases gradually, reaching 89.88% when the vinyl content is 17%. The grain size of β‐SiC decreases continuously with the increase in vinyl content, while the high‐temperature oxidation‐resistant properties of SiC ceramics obtained from different VHPCSs are not negatively affected. [ABSTRACT FROM AUTHOR]

With the appearance of new epoxy resins and amines, which are widely used for hardening epoxy compositions using energy-saving technology (at «ordinary» temperatures), on the world market, the targeted selection of these materials to provide the desired technological and operational properties becomes relevant. In order to predictively choose amine hardeners for epoxy resins, their quantum-chemical calculations were performed using the semi-empirical parameterized 3 (PM3) method. The energy value of the highest occupied molecular orbital (HOMO) of amines and the absolute value of the energy gap |Δ| (the absolute difference in energies between the HOMO of amines and the lower vacant molecular orbital (LUMO) of epoxy resins) were used. The relationships between the absolute value of the energy gap |Δ| and the main technological parameters of the curing process of dian epoxy resin ED-20 with individual amines were established with pairwise correlation coefficients of not less than 0.977. The evaluation of the activity of modified polyamines and their mixtures in hardening epoxy resins is proposed to be carried out based on the maximum temperature of the exothermic reaction of interaction between the epoxy groups of resins and the amine groups of hardeners. The possibility of adjusting the temperature of the exothermic hardening reaction of epoxy compositions and their «viability» time by introducing epoxy-containing diluents with different values of the LUMO energy was shown. [ABSTRACT FROM AUTHOR]

Liquid hydridopolycarbosilanes (LHPCS) with vinyl or allyl groups have attracted significant research interest due to their low curing temperature and high ceramic yield. In this study, allyl-terminated hydridopolycarbosilane (AHPCS) and vinyl-terminated hydridopolycarbosilane (VHPCS) were prepared by the Grignard coupling reaction and characterized by NMR and Fourier infrared spectroscopy (FTIR). And the curing reactions of AHPCS and VHPCS with or without initiators (dicumyl peroxide [DCP], tert-Butyl peroxybenzoate [TBPB]) or Karstedt catalyst were investigated using differential scanning calorimetry and in-situ FTIR. The main curing reactions of VHPCS and AHPCS are the double bond free radical polymerization and hydrosilylation reaction, respectively. The addition of initiators and Karstedt catalyst could promote the corresponding curing reaction and increase the weight residual at 1000°C. The thermal properties of the cured resins were investigated by thermogravimetric analysis. The addition of initiators and catalyst could significantly increase the weight residual of VHPCS and AHPCS, respectively. The addition of the Karstedt catalyst increased the weight residual of AHPCS from 75.6% to 83.1%. In addition, the addition of TBPB and DCP increased the weight residual of VHPCS from 74.2% to 81.2% and 80.2%, respectively. [ABSTRACT FROM AUTHOR]

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Resin transfer molding (RTM) process is a major molding process in the manufacture of resin-based composites, and the simulation of this process can play a key role in the process of optimization for the design of RTM parts. This paper independently developed a three-dimensional non-isothermal RTM simulation model based on the control volume/ finite element method (CV/FEM) on the basis of two-dimensional isothermal RTM program. Based on the Darcy equation, the continuity equation, the energy conservation equation, the curing reaction equation and multiple rheological curing models, the simulation model adopts semi-discrete method and three convergence criteria to effectively solve the problems of mold preheating and resin non-isothermal in the non-isothermal RTM simulation process. For the simulation problems such as viscosity changing and curing heat release during the filling process, the simulation function has reached the level of similar international products. After the application verifications of the flat plate test piece and casing simulation, this simulation model can simulate filling time, velocity and pressure of RTM process that is the same as the products in the world. This simulation model basically has the ability of simulation for the actual complex structure parts. [ABSTRACT FROM AUTHOR]

Considering the poor cohesiveness of the joint between pothole repair materials on asphalt pavement and old pavement, epoxy resin (EP) was toughened in this study, and a new composite resin material applicable to pavement repair was proposed. In particular, epoxy acrylic resin was prepared through the blending modification of acrylic resin and EP. The rheological properties of the composite resin were analyzed, and the influence of different acrylic acid contents on the toughness of the composite resin was discussed. Subsequently, the curing reaction process of the composite resin was explored via differential scanning calorimetry, and the theoretical curing process was determined. On this basis, the thermal stability of the composite resin was analyzed through thermogravimetric analysis. Results show that the tensile strength, elongation at break, and impact strength of the optimal composite resin are increased by 88.43%, 4202%, and 103.14%, respectively compared with those of EP alone, indicating that acrylic resin exerts a remarkable toughening effect on EP. The construction process parameters of the resin can be effectively predicted by measuring the curing reaction degree. The onset temperature of the resin is 101 ℃, and its thermal stability is favorable and can meet the application requirements of the resin in high-temperature weather during summer. The conclusions provide an important reference for follow-up research on pavement maintenance materials. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Atomic & Molecular Physics (1000-0364) is the property of Journal of Atomic & Molecular Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Considering its great industrial potential, epoxidized linseed oil (ELO) was crosslinked with different agents, both natural and synthetic: citric acid (CA, in the presence of water—W, or tetrahydrofuran—THF, as activator molecules) and Jeffamine D230, respectively, resulting bio-based polymeric matrices, studied further, comparatively, in terms of their properties, through different methods. Thermal curing parameters were established by means of Differential Scanning Calorimetry (DSC). Fourier transform Infrared Spectroscopy (FTIR) and DSC were used to identify the reactivity of each ELO-based formulation, discussing the influence of the employed curing systems under the conversion of the epoxy rings. Then, the obtained bio-based materials were characterized by different methods, establishing the structure–properties relation. Thermogravimetric analysis revealed higher thermal stability for the ELO_CA material when THF was used as an activator. Moreover, a higher glass transition temperature (Tg) with ~12 °C was registered for this material when compared with the one that resulted through the crosslinking of ELO with D230 conventional amine. Other important features, such as crosslink density, storage modulus, mechanical features, and water affinity, were discussed. Under the loop of a comprehensive approach, a set of remarkable properties were obtained for ELO_CA_THF material when compared with the one resulting from the crosslinking of ELO with the synthetic Jeffamine. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The irreversible curing reaction of thermosetting epoxy asphalt mixture (EAM) brings challenges to the construction of epoxy asphalt concrete (EAC) on the steel bridge deck, and the curing reaction degree (CRD) of EAM before compaction has a great influence on the compaction quality. The objective of this study is to investigate the effects of excessive CRD condition and uneven CRD condition of warm mix EAC on its field compaction. To achieve this goal, a field compaction model for EAC on a steel bridge deck was developed using discrete-element method (DEM) first. In the DEM model, a two-stage contact model that combined Burges model with the parallel bond model was used to characterize the thermosetting and viscoelastic behaviors of EAM, and the values of the contact model's parameters under different CRDs were determined by a trial calculation method based on Superpave gyratory compaction test. Subsequently, the field compaction process of cured EAM with different CRDs was simulated by changing the contact parameters' value, and the effects of excessive CRD condition and uneven CRD condition on the compaction quality were analyzed. Results show that the highly cured EAM is hard to be compacted unless larger compaction loads are adopted in the repeated compaction. Uneven CRD of EAM is prone to generate the mixture agglomeration, and it has negative effects on the compaction quality of the surrounding EAM. [ABSTRACT FROM AUTHOR]

Copyright of Chemija is the property of Lithuanian Academy of Sciences Publishers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the effects of polyetheramine (D230) functionalized graphene oxide loading on the curing reaction, thermal and mechanical properties of epoxy composites were studied and the correlation between structure and property of epoxy composite was established. In the functionalization of graphene oxide (GO), the effect of the mass ratio of D230 to GO on chemical properties of the functionalized GO was investigated. Results showed that D230 were successfully covalently grafted onto surface of two-dimensional functionalized GO sheet. The functionalized GO sheets prepared under optimal condition of D230/GO ratio of 1:1 dispersed evenly in epoxy composites, indicating the possibility of the epoxy composite fabrication by the solvent-free technique. The analysis of qualitative Cure Index suggested that epoxy composites were subjected to excellent curing. The quantitative evaluation of curing kinetics demonstrated that the functionalized GO exhibited a chemical facilitation on the curing reaction. However, the functionalized GO simultaneously physically restricted the curing reactivity, especially at high loading. These contributed to the improved interfacial properties and high toughness of the epoxy composites. Compared to neat epoxy, the epoxy composites showed effective tensile strength improvement of ∼10.0% (77.0 MPa), tensile modulus enhancement of ∼7.7% (3.34 GPa), flexural modulus increment of ∼12.1% (3.43 GPa), and flexural strength increment of ∼10.6% (124.3 MPa). This study demonstrated an effective and environment-friendly strategy to design GO reinforced epoxy composites with favorable dispersion and interfacial bonding, and it further clarified the relationship between the crosslinking network/interfacial structure and the mechanical properties of epoxy composites. [ABSTRACT FROM AUTHOR]

Natural fibers and particularly flax fibers have a great potential to replace glass fibers in composite materials. However, the interaction between these fibers and thermoset matrices remains unclear and results in a weak interface affecting the mechanical properties of the composite. This study was carried out to investigate the impact of natural fibers on the chemical reaction between the resin and the hardener, studying the interaction of fibers with each component separately to understand more precisely the phenomena involved. The results show that the contact with the fibers involves a change of the matrix properties that has been attributed to the water absorbed on their surface. On the one hand, water could modify amine functions of the hardener leading to a decrease of 40°C of matrix glass transition temperature (Tg). This issue could be corrected by adding a 16% excess of hardener. On the other hand, the water added to the resin could also accelerate the epoxide/amine reaction increasing slightly the Tg of the matrix and also generating weaker distinct networks of lower Tg by post-modification of the hardener. Therefore, the control of the water content in flax fibers is a crucial parameter for composite manufacturing. [ABSTRACT FROM AUTHOR]

In order to eliminate the deficiencies of the solvent-based cold patch asphalt mixture, this paper presented the cold patch asphalt mixture modified with waterborne epoxy resin (WER). Firstly, the new evaluation method were put forward based on its technical features and application requirements. Then the influence of different compositions and contents of WER on the cold patch asphalt liquid was evaluated by laboratory tests. Further, the pavement performance and workability of WER modified cold patch asphalt mixture were systematically evaluated. The results show that (i) WER can significantly improve strength, moisture susceptibility, high temperature performance and cohesion. However, the inappropriate addition may lead to poor storability and low temperature performance. So the optimal WER content is recommended 1.2–1.8 wt%, and its component ratio of epoxy resin to curing agent is 3:1. (ii) Different WER components produce different performances of mixture. The EP-20 + HGC brings about higher curing strength, excellent high temperature performance and storability. In comparison, the mixture modified with EP-20 + HGA owns preferable initial strength and moisture susceptibility. In the practical project, it is necessary to choose suitable WER considering the performance deficiency of cold patch materials and maintenance needs. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the curing process of hydroxyl‐terminated polyether (HTPE) with different curing agents, aliphatic triisocyanate (N100) and toluene diisocyanate (TDI), the crosslink density (XLD) and chemical processes of the curing reactions have been investigated by low‐field NMR spectroscopy and FTIR spectroscopy, respectively, while the mechanical properties of those two cure systems were studied as well. The results show that, for either HTPE/N100 or HTPE/TDI, the higher curing temperature leads to the shorter curing time to reach stability of XLD, while the final XLD decreases by increasing the temperature. The XLD and tensile strength of HTPE/TDI are both lower than those of HTPE/N100, although curing reaction of the HTPE/TDI system is faster and more complete, as seen from FTIR spectra. Besides, the tensile strength of HTPE/N100 based propellant attains the maximum value of 0.64 MPa at NCO/OH ratio of 1.4, while the maximum XLD value of 6.5× 10−5 mol⋅cm−3 was obtained at the same time. The XLD is well correlated in tensile strength with the variation of NCO/OH, that suggests regulation of XLD value may be an effective way to optimize the curing conditions for improving mechanical properties of HTPE/isocyanate‐based propellants. [ABSTRACT FROM AUTHOR]

Epoxy/polysufone (PSF) composites cured with 4,4'‐diaminodiphenyl sulfone (DDS) and 4,4'‐diaminodiphenyl methane (DDM) were fabricated, and the effect of dual curing reaction of diamines with epoxy on morphology, mechanical, and thermal performance was investigated. DSC results indicated that DDM was more reactive than DDS and the activation energy decreased with the rising of DDM content. Structures with small domain size at the early stage of phase separation were fixed by the fast epoxy‐DDM reaction. When the DDM content was elevated to a high level, large dual structures were changed to fine bicontinuous structures, which was favorable to improve the mechanical property. The mechanical performance of epoxy composites was enhanced and the maximum values were achieved when the DDM/DDS ratio was located at 75/25 (PSF/DDS0.25‐DDM0.75). The flexural and tensile strength relative to epoxy/DDM system were enhanced more than those relative to epoxy/DDS, while the increase in toughness was the opposite. TGA measurement showed that thermal stability of epoxy/PSF composites was improved because of the restricting effect of continuous PSF domains on thermal motion of epoxy. DMA analysis exhibited two relaxation peaks for PSF/DDS0.25‐DDM0.75, which could be attributed to the formation of phase separated morphology and epoxy network with different cross‐link density. [ABSTRACT FROM AUTHOR]

Thermosetting resins like polyfurfuryl alcohol (PFA) tend to get prematurely cured and viscous during storage. Understanding a resin shelf-life is very helpful but no definite and validated method could be found in both scientific literature and standard methods. Cure kinetics of PFA was determined through tracing the complex viscosity changes as a function of time at elevated temperatures of 160, 170, 180, 190 and 200 °C. Adopting an empirical statistical approach, shelf-life of PFA resin at ambient temperature was estimated using the accelerated cure profiles. To this end, two functions were fitted on experimental results and then the empirical cure reaction rate constants at different temperatures were extrapolated to 25 °C. Subsequently, the viscosity versus time profiles were built for curing the resin at ambient temperature. The time interval corresponding to a viscosity range of 10–12.5 Pa.s was considered as the practical shelf-life of the resin at ambient conditions. The findings were validated by comparing the model results to the real-time, experimentally-obtained values. [ABSTRACT FROM AUTHOR]

Superhydrophobicity of alloy surfaces is generally determined by the low-energy chemical composition and geometric structure of the surface. The appropriate geometry on alloy surfaces can be easily constructed via chemical etching methods. However, the subsequent low-energy modifications for pre-etched alloys are time-consuming or expensive, thus preventing their further application. Here, we prepared superhydrophobic alloy surfaces based on combining wet chemical etching and room temperature vulcanized (RTV) silicone treatment. Compared to traditional immersion methods, RTV silicone treatment for superhydrophobic 6061 Al alloy surfaces needs only 30 s, which is several thousand times faster than stearic acid or polymethyl triethoxy silane solution treatment. Mechanisms of RTV silicone treatment were investigated. The results show that dip-coating modification is different from these traditional methods. We found that the optimized proportion for RTV silicone rubber is HPDMS, PMTSi, and DBTDL with hexane solvent (HPDMS:PMTSi:DBTDL:hexane = 4:3:1:46, weight ratio), and the water contact angles of treated surfaces of pre-etched 6061 Al alloy, pure Al, and steels are 159° ± 2.7°, 168° ± 1.2°, and 169° ± 1.5°, respectively. Herein, our results demonstrate a facile, low-cost strategy to fabricate superhydrophobic alloy surface that is notable and easy to scale up for industrial applications. [ABSTRACT FROM AUTHOR]

Featured Application: Microcapsule based self-healing system is developed for intelligent repair of microcracks or/and damage in cementitious composites. Self-healing cementitious composites have been developed by using microcapsules. In this study, the effect of the healing agent on the crosslinking and curing reaction kinetics was analyzed. The effect of the diluent n-butyl glycidyl ether (BGE) on the reaction was investigated for five fractions, namely 10.0%, 12.5%, 15.0%, 17.5%, and 20.0% mass fractions to epoxy resin. The Kissinger and Crane equations were used to obtain the activation energy and reaction order with different mass fractions of diluent, as well as the kinetic parameters of the curing reaction. The optimal fraction of BGE was determined as 17.5%. Likewise, the effect of the curing agent MC120D on the reaction kinetics was investigated for 10%, 20%, 30%, 40%, and 50% mass fractions to the diluted epoxy resin. The optimal fraction was determined as 20%. The mechanism of the curing reaction with the healing agent was investigated. The infrared spectra of the cured products of 20% MC120D with BGE/E51 (0.0%, 12.5%, 15.0%, 20.0%, 100%) were analyzed. It is shown that not only the epoxy resin E-51 was cured, but also that the BGE was involved in the cross-linking reaction of the epoxy resin E-51 with MC120D. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gels were obtained from resol type phenolic resins, with resorcinol, formaldehyde and lignin as precursors. Thermal response was evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and curing kinetics were determined from the SDTA curves using Flynn-Wall-Ozawa and Friedman iso-conversional models. Additionally, it was used Fourier transform infrared spectroscopy (FTIR) to evaluate the progress of the curing reaction. These analyzes were performed for two gels, one of them prepared with lignin (lignin resin), and a reference (resorcinol resin). Lignin resins tend to be more thermally stable than resorcinol resins. Average values found for activation energy of the curing processes are 55.07 kJ mol−1 and 60.60 kJ mol−1 for resorcinol resin and lignin resins respectively using Flynn-Wall-Ozawa method; values of 51.94 kJ mol−1 and 53.14 kJ mol−1 were obtained using Friedman method. It was possible to conclude that the lignin affects positively the thermal stability of the resin; the curing reaction takes place in the first six hours and the Flynn-Wall-Ozawa model fits better. [ABSTRACT FROM AUTHOR]

4,4′-Diphenylmethane bismaleimide (BMI)/2,2′-diallylbisphenol A (DABPA) resin was modified with a multifunctional thiol containing isocyanuric ring and long-chain aliphatic unit (tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate (TEMPIC)). To investigate the relationship of the curing reaction and properties of cured BMI/DABPA resin modified with TEMPIC, the temporal change in the functional groups during the curing reaction process was analyzed using Fourier transform infrared analysis. Despite the decreased cross-link density with increasing TEMPIC concentration, the glass transition temperature of BMI/DABPA resin was not decreased by modification with TEMPIC. The storage modulus of BMI/DABPA/TEMPIC resin maintained a value on the order of 109 Pa in the rubber region, which is similar to that of the unmodified resin. The fracture toughness and flexural strength were also improved by modification with TEMPIC. Moreover, the observation of the fracture surface of BMI/DABPA/TEMPIC resin using scanning electron microscopy showed a uniform structure with no phase separation. These results were consistent with the single α-relaxation peak in the loss tangent curve of the dynamic viscoelastic behavior. [ABSTRACT FROM AUTHOR]

A green analytical method was applied to evaluate the incompatible hazard for 3,4-epoxycyclohexane methyl-3′4′-epoxycyclohexyl-carboxylate (EEC) mixed with its synthetic materials. During the manufacturing process, numerous accidents of human poisoning, explosion, or fire have been reported due to the chemical's incompatible reaction. A calorimetric application and product's analysis approach have been employed to obtain related information for the incompatible hazard investigations of chemicals. This study also used nonlinear regression analysis to establish a kinetic model. The results proved that HSO can cause an abnormal curing reaction and release significant amounts of heat of the curing reaction for EEC, increasing the occurrence probability of accidents. [ABSTRACT FROM AUTHOR]

ABSTRACT A uniform dispersion of reactants is necessary to achieve a complete reaction involving multicomponents. In this study, we have examined the role of plasticizer in the reaction of two seemingly unlikely reactants: a highly crystalline hexamethylenetetramine (HMTA) and a strongly hydrogen bonded phenol formaldehyde resin. By combining information from NMR, infrared spectroscopy and differential scanning calorimetry, we were able to determine the role of specific intermolecular interactions necessary for the plasticizer to dissolve the highly crystalline HMTA and to plasticize the phenol formaldehyde resin in this crosslinking reaction. The presence of the plasticizer increased the segmental mobility, disrupted the hydrogen bonded matrix, and freed the hydroxyl units, which further increased the solubility of the HMTA. Both the endothermic and exothermic transitions are accounted for in the calorimetric data obtained. For the first time, it is possible to obtain the effective molar ratio of each component needed to complete the crosslinking reaction efficiently. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1519-1526 [ABSTRACT FROM AUTHOR]

ABSTRACT This study demonstrates that the curing reaction of thermosetting polymers, in particular, epoxy resins cured with aliphatic amines, can be characterized by different multiple-quantum (MQ) NMR experiments performed in low-field spectrometers. Measurements of the curing reaction at 40 °C, 70 °C, and 100 °C are carried out to obtain the kinetic parameters like induction time, vitrification time, polymerization rate, and activation energy being consistent with data obtained by other traditional and complementary techniques. Besides, it is demonstrated that 1H MQ-NMR spectroscopy is a successful approach to overcome the experimental challenge arising from the characterization of high dipolar-coupled polymers to study the network structure and segmental dynamics of thermosetting polymer networks. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1324-1332 [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) spectroscopy is a rapid and nondestructive method for the simultaneous measurement of different constituents in resin matrix polymer composites. This strategy has been applied in the synthesis of resin matrix polymer composites. In this article, we mainly review the control of curing reaction kinetics of the phenolic, epoxy resin, polyester resin, polyurethane, and other polymer resin based on NIR spectra, which is important to control the quality of the resin matrix polymer composites during synthesis. [ABSTRACT FROM PUBLISHER]

Recent experimental results showed that the Tg of cured resin scarcely decreased and the impact strength of resins increased by over 50% when a tetrafunctional epoxy named N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl ether (TGDDE) was introduced to an appropriate flexible chain from a dimer fatty acid (DFA). In order to understand the reason for this phenomenon, the modification and the chemical structure of the prepolymer together with the curing reaction and the viscoelasticity of the cured resins were studied in detail in the present work. The results indicated that the modification would help the prepolymer improve its molecular mobility. As a result, the resins could be further cured, resulting in the cross-linking density increasing. This is because the curing efficiency was increased, but the tetrafunctional epoxy was not cured completely due to its large steric hindrance. Moreover, the flexibility of some parts of the networks was improved, which was beneficial for the toughness of the cured resins. Therefore, the toughness of the tetrafunctional resin was improved with little influence on the thermal properties when the epoxies were modified with an appropriate content of DFA. [ABSTRACT FROM AUTHOR]

Purpose -- The purpose of this paper was to check effectiveness of amine functional chloroaniline acetaldehyde condensate (AFCAC) as a new curing agent for diglycidyl ether of bisphenol A (DGEBA) resin. For this purpose, first AFCAC was synthesised, characterised and then curing reaction was carried out. Design/methodology/approach -- Equimolecular mixture of AFCAC and DGEBA was subjected to curing reaction, and the reaction was followed by differential scanning calorimetry (DSC) analysis. The kinetic studies of this curing reaction were also carried out from those DSC exotherms. The mechanical properties, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) of cured epoxy were also reported. Findings -- DSC results reflected the effective first order curing reaction of AFCAC with epoxy resin. Mechanical properties reflected appreciable rigidity of AFCAC cured epoxy matrix and TGA showed that the cured epoxy networks were thermally stable up to around 297°C. Research limitations/implications -- The curing agent AFCAC was synthesised by using chloroaniline and acetaldehyde in acid medium. There are some limitations for this procedure. The synthetic procedure is pH dependent. So reaction cannot be done at any pH value. The reaction must also be carried out at room temperature without any heating. To obtain low molecular weight curing agent, chloroaniline and acetaldehyde cannot be taken in equimolecular ratio because the equimolecular mixture of them produces high molecular weight condensate. This was shown in our previous publication. Some implications are also there. By changing amine and aldehyde other curing agents could be synthesised and the curing efficiency of those for epoxy resin could also be studied. Originality/value -- Experimental results revealed the greater suitability of AFCAC as curing agent for DGEBA resin and novelty of AFCAC cured matrix in the field of protective coating, casting, adhesives, etc. [ABSTRACT FROM AUTHOR]

The curing process of diglycidyl ether of bisphenol A (DGEBA)-isophoronediamine (IPDA) system filled with different contents of Fe nanoparticles (nano-Fe) has been investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy analysis in order to understand the effect of nano-Fe. These studies revealed that high percentage of the nanofiller, i.e. 10 %, results in improved epoxy matrix as evidenced by increasing in the reaction heat and conversion degree. Kinetics of DGEBA/IPDA/10 % nano-Fe cure was studied by calorimetry measurements at isothermal mode. Isothermal kinetic parameters, including k, k, m, and n were determined and it was shown that the reaction kinetics could be expressed well by d α/d t = ( k + k α)(1− α) which called Kamal model. The results also showed that the diffusion control does not occur. The excellent fitting Kamal model with experimental data at the end of the isothermal cure process could be mentioned as evidences here. The dispersion of 10 % nano-Fe into epoxy matrix was analyzed by atomic force microscopy observations. [ABSTRACT FROM AUTHOR]

The influence of the end groups of two liquid rubbers on curing kinetics, morphology, and hardness behavior of diglycidyl ether of bisphenol-A based epoxy resin (DGEBA) has been studied. The rubbers are silyl-dihydroxy terminated (PDMS- co-DPS-OH) and silyl-diglycidyl ether terminated (PDMS-DGE). Crosslinking reactions, investigated by shear rheometry, ranged 90-110 °C, using a constant concentration (5 phr) of liquid rubbers and 1,2-Diamino cyclohexane (1,2-DCH) as hardener agent. The gel time, t, of the neat epoxy significantly decreased when adding the elastomers, more so for the silyl-dihydroxy terminated elastomer; at 110 °C the reaction was nearly complete before rheological test started. The results suggest that the elastomers induced a catalytic effect on the curing reaction. Scanning electron microscopy revealed phase separation of the elastomer during the curing reaction with rubber domains about 5 μm size. However, the DGEBA/dihydroxy terminated elastomer composite cured at 110 °C exhibited a homogenous morphology, that is, the rapid reaction time would not allow for phase separation. Water contact angle tests evidenced either more hydrophilic (silyl-diglycidyl ether terminated rubber) or more hydrophobic (silyl-dihydroxy terminated rubber) behavior than the neat epoxy. The latter effect is attributed to the presence of aromatic rings in the backbone structure of PDMS- co-DPS-OH. Microindentation measurements show that the elastomers significantly reduced the hardness of the epoxy resin, the DGEBA/ether terminated composite exhibiting the lowest hardness values. Moreover, hardness increased as reaction temperature did, correlating with a reduction of microdomains size thus enabling the tuning of mechanical properties with reaction temperature. [ABSTRACT FROM AUTHOR]

With our multiscale simulation strategy developed previously, we study the curing reaction of soybean oil and styrene to prepare a thermosetting resin. From atomistic simulation details, we estimate the parameters used in coarse-grained (CG) simulations. Then, with the mesoscopic dissipative particle dynamics simulation, the CG network structure and average cross-linking density of a material can be obtained. Finally, the reverse-mapping scheme of the CG structure to atomistic representation is carried out to analyse the mechanical properties and the glass transition temperature of the system. We find in such a system that the molar ratio of double bonds in the two reactants plays a significant role in determining the physical properties of a product. These results shed light on improved control and design of thermosetting resin material via curing reaction of soybean oil. [ABSTRACT FROM AUTHOR]

In order to improve the dielectric and overall properties of cyanate ester (CE) resin, octa(aminopropyl)silsesquioxane (POSS-NH2) was used to modify CE. A series of POSS-NH2/CE hybrids containing different contents of polyhedral oligomeric silsesquioxane (POSS) were elaborated by melt casting and then curing. The curing kinetics and reaction mechanisms of the resin systems were studied using Fourier-transform infrared (FT-IR). Dielectric properties, thermal stability, and hot/wet resistance of the hybrids have been investigated. FT-IR results show that both temperature and POSS content may influence the curing reaction of CE. POSS-NH2 mainly displays the catalytic effect at higher temperature (220°C). Dielectric results indicate that NC1 containing 1 wt% of POSS displays not only the lowest dielectric constant but also the lowest dielectric loss. The increase in POSS content leads to significant increase in glass transition temperature (Tg) at lower POSS content (≤5 wt%). However, further increase in POSS content (>5 wt%) does not lead to great increase in Tg. Besides, all the POSS-NH2/CE hybrids show lower water absorption than that of CE. [ABSTRACT FROM AUTHOR]

Octaepoxysilsesquioxane (POSS-Ep) was first synthesized by the hydrolysis and condensation of γ-[(2,3)-epoxypropoxy]propyltrimethoxysilicane (KH-560) with the presence of ethanol and HCl at 55°C for 72 h. Then, it was cured with 4,4′-diaminodiphenylsulfone (DDS) and methylnadic anhydride (MNA), respectively. The curing reactions between POSS-Ep and DDS or MNA were investigated by FTIR. Thermal stability of the cured nanocomposites was studied by TGA. The micromophologies of the obtained hybrids were observed by SEM. FTIR results show that POSS-Ep can be cured completely with DDS or MNA to obtain the final organic-inorganic (O-I) hybrids after the same experimental curing cycle: 120°C/2 h + 140°C/2 h + 160°C/2 h + 180°C/2 h + 200°C/2 h. TGA results show that POSS-Ep/DDS hybrid displays better thermal stability than that of POSS-Ep/MNA hybrid. Initial thermal degradation temperature (Tdi) of POSS-Ep/DDS hybrid is 420°C, 195°C higher than that of POSS-Ep/MNA (225°C). SEM images of the fracture surfaces of the hybrids suggest the cured POSS-Ep possesses good mechanical properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

In order to understand the strength developing law of the epoxy asphalt mixture, a curing reaction model of the epoxy asphalt binder was proposed based upon the thermokinetic analysis. Given some assumptions, the model was developed by applying the Kissinger law as well as Arrhenius equation, and the differential scanning calorimetry was performed for estimating the model parameters. To monitor the strength development of the epoxy asphalt mixture, a strength test program was employed and then results were compared to those produced from the proposed model. The comparative evaluation shows that a good consistency exists between the outputs from test program and the proposed model, indicating that the proposed model can be used effectively for simulating the curing reaction process for the epoxy asphalt binder and predicting the strength development for the epoxy asphalt mixture. [ABSTRACT FROM AUTHOR]

We introduce a reaction model for use in coarse-grained simulations to study the chemical reactions in polymer systems at mesoscopic level. In this model, we employ an idea of reaction probability in control of the whole process of chemical reactions. This model has been successfully applied to the studies of surface initiated polymerization process and the network structure formation of typical epoxy resin systems. It can be further modified to study different kinds of chemical reactions at mesoscopic scale. [ABSTRACT FROM AUTHOR]

Novolac resins of varied ortho to para (O/P) ratios were prepared and characterized with FTIR and 13C-NMR. The nonisothermal curing reactions of these novolac resins with hexamethylenetetramine (HMTA) were studied in detail using a dynamic differential scanning calorimetry (DSC) technique at a series of heating rates. The global activation energies of the reactions were determined with the Ozawa, Kissinger methods, respectively; additionally, Kissinger-Akahira-Sunose (KAS) isoconversional kinetic approach was used to obtain activation energy as a function of conversion. The results showed that the peak temperatures of the exothermic reactions and global activation energies decreased with increasing O/P ratios, which indicated that the higher the O/P ratio was, the faster the curing speed. In addition, the results from the KAS analysis exhibited that the activation energies increased quickly with conversion at the later reaction stage, which was likely associated with the diffusion-controlled kinetics. [ABSTRACT FROM AUTHOR]

A new liquid crystalline thermoset (LCT) based on 1,3,4-oxadiazole was prepared from liquid crystalline epoxy resin containing oxadiazole and diaminodiphenyl methane. The LCT was characterized and compared with the conventional thermoset. The Time-Temperature Transformation diagram was constructed to determine an appropriate set of cure cycles. The goal of this paper was centered on the evaluation of the mechanical performances of this new class of thermoset. In the case of LC thermoset, a higher Tg and good fracture resistance were noticed than that of the conventional thermoset. The LC thermoset exhibited higher thermal stability when compared with the conventional non-LC thermosets. The results tempted to consider the LCT materials as potential candidates for advanced composites. [ABSTRACT FROM AUTHOR]

To answer the question "How does lanthanide doping in iron oxide affect cure kinetics of epoxy-based nanocomposites?", we synthesized samarium (Sm)-doped Fe3O4 nanoparticles electrochemically and characterized it using Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-Ray analysis (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy analyses (XPS). The magnetic particles were uniformly dispersed in epoxy resin to increase the curability of the epoxy/amine system. The effect of the lanthanide dopant on the curing reaction of epoxy with amine was explored by analyzing differential scanning calorimetry (DSC) experimental data based on a model-free methodology. It was found that Sm3+ in the structure of Fe3O4 crystal participates in cross-linking epoxy by catalyzing the reaction between epoxide rings and amine groups of curing agents. In addition, the etherification reaction of active OH groups on the surface of nanoparticles reacts with epoxy rings, which prolong the reaction time at the late stage of reaction where diffusion is the dominant mechanism. [ABSTRACT FROM AUTHOR]

The influence of pressure on the polycondensation reaction between novolac resin (N) present in commercially available moulding compounds and hexamethylenetetramine (HMTA) was studied up to 80 bars under air and in an inert atmosphere. For a low HMTA content (N/HMTA=98/2 mass ratio) high pressure enables the detection of two successive curing reactions. With increasing HMTA content the peak due to the first curing reaction becomes less pronounced at high pressure, while the enthalpy of the second increases. In an inert atmosphere both curing reactions are well observable even at ambient pressure and for lower HMTA content take place at lower temperatures, as expected. For the sample with N/HMTA=98/2 the curing reaction was followed using TG-MS. [ABSTRACT FROM AUTHOR]

Liquid crystalline epoxy resin (LC epoxy resin) - p-phenylene di{4-[2-(2,3-epoxypropyl)ethoxy]benzoate} (PEPEB) was synthesized. The mixture of PEPEB with bisphenol-A epoxy resin (BPAER) was cured with a curing agent 4,4-diamino-diphenylmethane (DDM). The curing process and thermal behavior of this system were investigated by differential scanning calorimeter (DSC) and torsional braid analysis (TBA). The morphological structure was measured by polarizing optical microscope (POM) and scanning electron microscope (SEM). The results show that the initial curing temperature Ticu (gel point) of this system is 68.1°C, curing peak temperature Tpcu is 102.5°C, and the disposal temperature Tfcu is 177.6°C. LC structure was fixed in the cured epoxy resin system. The curing kinetics was investigated by dynamic DSC. Results showed that the curing reaction activation energy of BEPEB/BPAER/DDM system is 22.413 kJ/mol. The impact strength is increased 2.3 times, and temperature of mechanical loss peak is increased to 23°C than the common bisphenol-A epoxy resin, when the weight ratio of BEPEB with BPAER is 6 100. [ABSTRACT FROM AUTHOR]

Thermosetting resins are converted into three-dimensional networks via a polymerisation reaction known as cure. This reaction determines the resin morphology that, in turn, will determine the physical, electrical, and mechanical properties of the cured material. Moreover, the cure reaction of thermosets is exothermic and polymers exhibit low thermal conductivity so the temperature and rate of reaction can vary considerably within the curing mass. Simulations of the behaviour of these materials require analytical models accurately describing its cure kinetics. An integrated thermal-kinetic model is presented to study photo-initiated curing reactions and determine different aspects associated with these reactions, describing both the heat transfer phenomenon all along the reaction and the cure kinetics. This model is sensitive to the resin composition, temperature and light intensity, apart from describing the main events occurring during cure reactions. The kinetic model and the law of the conservation of energy are coupled, while the integrated model is numerically solved. [ABSTRACT FROM AUTHOR]

The liquid crystalline epoxy resin p-phenylene di[4-2-(2,3-epoxypropyl)ethoxy] benzoate (PEPEB) was synthesized. The curing behavior of the liquid crystalline epoxy resin (LCER) with 4,4-diaminodiphenylmethane (DDM) was studied by fourier transform infrared (FTIR), differential scanning calorimetry (DSC), and torsional braid analysis (TBA). Morphology of curing product was observed by polarized optical microscopy (POM) at different temperatures. Nonisothermal curing kinetics of this system were investigated by DSC. Results show that the PEPEB has a smectic liquid crystalline structure, and the melting point, T m , is 119°C, the clearing point is 184°C. The cured-system's gel point, T I , is 83.5°C; cure temperature, T P , is 111.6°C; and the disposal temperature, T f , is 145.8°C; activation energy of curing reaction is 4.84 KJ/mol. Observation by POM shows that with the upgrade of initial curing temperature, the filament structure of this system transferred from anisotropy to isotropy. [ABSTRACT FROM AUTHOR]

The curing reaction of bisphenol A type novolac epoxy resin (bis-ANER) with 4,4′-diaminodiphenyl sulfone (DDS) was investigated with Fourier-transform infrared (FTIR) spectroscopy. It was found that the obvious structure changes involve the disappearance of epoxide groups and increase of hydroxyls. Thermal degradation of the bis-ANER/DDS network was studied with thermogravimetry in both dynamic air and nitrogen atmospheres. The degradation takes place in two steps in air but in only one step in nitrogen. FTIR measurement was carried out to identify the changes in the structure during the degradation at different steps. In addition, the thermal degradation reaction mechanism of bis-ANER/DDS with the Coats-Redfern method showed that the kinetic model function of the thermal degradation obeys the Avrami-Erofeev model equation, that is, g (α) = [-ln(1 - α)] 2/3 . [ABSTRACT FROM AUTHOR]

The curing reaction of the diglycidyl ether of 2,7-dihydroxy-naphthalene (2,7-DGEDHN) epoxy mesogenic resin, in the presence of sulfanylamide (SAA), diaminopyridine (DAP) and diaminodiphenylsulfone (DDS) as curing agents, was studied by differential scanning calorimetry, optical microscopy and X-ray diffraction. The curing reaction of 2,7-DGEDHN/SAA mixture led to a texture of nematic-like structure of the Schlieren type. The mixture 2,7-DGEDHN/DAP on curing presents a high-density smectic-like structure of the Schlieren type. The curing reaction of the 2,7-DGEDHN/DDS mixture led to a network without liquid crystalline properties. [ABSTRACT FROM AUTHOR]

Here, we propose a novel attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy method for simultaneously monitoring the curing reaction and the diffusion behavior of curing agents at the surface of rubber in real-time. The proposed scheme was demonstrated by fluorine rubber (FKM) and FKM/carbon nanotube (CNT) nanocomposites with a target curing agent of triallyl-isocyanurate (TAIC). The broadening and the evolution of the C=O stretching of TAIC were quantitatively analyzed to characterize the reaction and the diffusion. Changes in the width of the C=O stretching indicated the reaction rate at the surface was even faster than that of the bulk as measured by a curemeter. The diffusion coefficient of the curing agent in the course of heating was newly calculated by the initial increase in the absorbance and our model based on Fickian diffusion. The diffusion coefficients of TAIC during curing were evaluated, and its temperature and filler dependency were identified. Cross-sectional ATR-FTIR imaging and in situ ATR-FTIR imaging measurements supported the hypothesis of the unidirectional diffusion of the curing agent towards the heated surface. It was shown that our method of in situ ATR-FTIR can monitor the degrees of cure and the diffusion coefficients of curing agents simultaneously, which cannot be achieved by conventional methods, e.g., rheological measurements. [ABSTRACT FROM AUTHOR]

Unsaturated polyester resin (UP) is a critical polymer material in applications of many fields, such as the chemical industry, military, and architecture. For improving the mechanical properties, some hardeners, such as methyl ethyl ketone peroxide (MEKPO) or tert-butyl peroxy-2-ethylhexanoate (TBPO), can trigger the curing reaction in UP polymerization, which causes that UP changes the structure from monomer to polymer. However, polymerization is a strong exothermic reaction, which can increase the risk of thermal runaway reaction in UP. Therefore, the mechanisms and characteristics in the thermal runaway reaction of UP mixed with hardeners should be studied for preventing and controlling UP explosion. The thermal hazards of UP mixed with hardeners were determined by thermogravimetric analyzer (TGA) and differential scanning calorimetry (DSC) analysis. According to the results, UP mixed with MEKPO exhibited a more violent mass loss and exothermic reaction than UP mixed with TBPO. Furthermore, the thermal runaway reactions of UP mixed with MEKPO or TBPO with different mixing proportions of 1:1, 3:1, and 5:1 were determined. Irrespective of MEKPO or TBPO, the mixing proportions of 3:1 exhibited a high onset temperature and low enthalpy of curing reaction (ΔHexo). This demonstrated that this proportion was safer during UP polymerization. The results of this study can provide useful information for preventing UP explosion and developing polymerization technology. [ABSTRACT FROM AUTHOR]