Properties Of Epoxy System Research Articles

Investigating the effect of silica aerogel content on the mechanical properties of epoxy resin system

Investigating the effect of silica aerogel content on the mechanical properties of epoxy resin system

DGEBA/imidazolium ionic liquid systems: the influence of anions on the reactivity and properties of epoxy systems

Imidazolium salts containing , , , , or ionic liquids were blended with an epoxy prepolymer, dyglycidylether of bisphenol A (DGEBA) to obtain a series of compositions. To characterize the resulting mixtures and determine the influence of the imidazolium anion on the reactivity and properties of epoxy systems, we performed the following analyses and tests: (i) differential scanning calorimetry (DSC), to determine the curing reaction characteristics, (ii) in situ fourier-transform infrared spectroscopy (FTIR), to assess chemical structure changes, (iii) mechanical property testing of the hardened epoxy material, and (iv) thermogravimetric analysis (TGA). The DSC and FTIR analyses indicate that [Hmim]BF4, and [Hmim]PF6 cannot induce the epoxy ring opening reaction and thus these materials are unable to function as epoxy curing agents. In contrast, the imidazolium ionic liquids [Hmim]FeCl4, [Hmim]N(CN)2, and [Hmim]Zn2Cl5 independently promote the epoxy ring opening reaction. TGA analyses show that the cured DGEBA/[Hmim]Zn2Cl5 system exhibits thermal stability similar to the cured DGEBA/[Hmim]FeCl4. These results can provide an essential reference not only for studying the synergistic effect of [C6mim]FeCl4/mixed-amines on the curing process of epoxy systems and the mechanism of the ring opening of epoxides with [C6mim]FeCl4/mixed-amines, but also for designing new epoxy curing systems.

Cure Properties of Naphthalene-Based Epoxy Resin Systems with Hardeners and Latent Catalysts for Semiconductor Packaging Materials

The cure properties of naphthalene-based epoxy resin (EXA-4700) systems with different hardeners and latent catalysts were investigated. The latent catalysts used in this study were tetraphenyl phosphonium-thiocyanate (TPP-SCN) and 2-ethyl-4-methyl imidazolium tetraphenyl borate (EMZ-K). The cure kinetics of these systems were analyzed by dynamic and isothermal data from the Differential Scanning Calorimetry (DSC) experiments, and the kinetic parameters of all systems were reported in generalized kinetic equations with diffusion effects. Thermal expansion coefficients of these epoxy systems were obtained by mean of Thermo Mechanical Analyzer (TMA) measurement. The conversion reaction rate of EXA-4700 system with TPP-SCN is higher than that with EMZ-K, irrespective of the location of hydroxyl group in naphthol hardeners or the differences in cure mechanisms between these latent catalysts. The thermal expansion coefficient in low temperature region (α1) of EXA-4700 resin systems with 2,7-naphthol as a hardener is lower than that with 1,6-naphthol. The cure properties of these epoxy resin systems with different hardeners and catalysts were investigated with respect to the curing molecular structure.

Study on Processing Properties of Epoxy Resin System in VARI

As a low cost moulding technology, VARI is widely used to produce advanced composite materials. At the same time, the particularity of VARI process make it have particular requirements on resin system. Epoxy resin system attracts extensive attention because of its good process performance. Curing reaction and rheological behavior of epoxy resin system were studied by DSC and viscosity experiments. The results showed that resin viscosity decreased from 2600 mPa•S at 15°C to 600mPa•S at 40°C . Viscosity of resin system rose about 0.5Pa•s within the first 2h. Gel time shortened dramatically when the temperature exceed 60°C. the curing temperature is 60°C be based on DSC curve and gel time-temperature curve. Resin cast plate of epoxy resin system has good mechanical properties of compression strength.

Experimental study of epoxy repairing of cracks in concrete

Cracks in concrete structures have always posed a big threat on the durability of concrete. Cracking of concrete is a random process, highly variable and influenced by many factors. Among the crack repair methods is the use of epoxy either by injection or by gravity filling in order to bond the crack and restore its structural integrity. Prior to the use of epoxy compounds and due to their versatility and the wide range of available physical and chemical properties of epoxy resin systems, one has to be completely aware and informed before entering the world of epoxies; other than crack repair, epoxy compounds have found a wide variety of uses in the concrete industry. In this study, 15 concrete cubes, six including cracks without repair, six including cracks bonded with gravity filled epoxy and three with no cracks were crushed and their compressive strengths were obtained. It was found that the cracks caused a reduction in compressive strength up to 40.93% whereas the epoxy system, when properly applied, restored the compressive strength by decreasing the reduction down to 8.23%.

Properties of epoxy systems with clay nanoparticles

AbstractLow molecular epoxy resin was mixed with different concentrations of montmorillonite clay with alkylamine‐modified surface. The presence of the clay nanoparticles influences the gel time of the amine cured resin as well as the mechanical properties. Toughness and modulus, both in the glass and the rubberlike region, increase with clay concentration. An increasing amount of lower mobility phase with increased clay concentration was observed.

Properties of Epoxy Systems with Clay Nanocomposites

Different types of montmorillonite clays are often used for the modification of thermoplastic polymers. In the case of epoxy systems, the presence of the clays can complicate the cure process. Therefore, the influence of montmorillonite concentration and the temperature regime on the cure rate and mechanical properties of the composite material obtained is investigated in this paper.

Dynamic mechanical studies on epoxy resins cured by electron beam radiation

Dynamic mechanical analyses on electron beam (EB)-cured epoxy resins were made in the paper. Through the studies on variation rules of gel fraction, tanδ and storage modulus for varied samples, the important effects of EB radiation dosage, initiator dosage, chemical structure, molecular weight and distribution, and heat treatment on curing reaction and properties of epoxy resin systems have been obtained. Under low radiation doses, the gel fraction, glass transition temperature (Tg) and high temperature modulus of cured epoxy resin increase with increasing radiation dose and initiator dosage. The crosslinking density of epoxy resin decreases slightly with increasing molecular weight. When radiation doses increase, the molecular weight has a little influence on the increasing of curing level and an optimal dosage of initiator appears. The experimental results indicate that the radiation reactivity of epoxy resins is directly associated with their chemical structures. Under the same radiation dose, the reaction extent in sample with high polydispersity is higher than that in low polydispersity sample, but the degree of homogeneity in crosslinking structure is lower. When the EB-cured epoxy resin is heated, the crosslinking density is enhanced. If the temperature of heating treatment exceeds the thermal-initiating temperature of initiator, the local thermal-crosslinking network can be formed in resin system.

Surface properties of epoxy systems, 2. Evolution of epoxy‐amine system with reaction time

AbstractWith the plate method we determined dynamically the surface tension of different epoxy‐amine systems. After different critical observations about the validity of this type of measurement during the reaction time, we were able to correlate the evolution of the surface tension with epoxy conversion. For epoxy systems based on cycloaliphatic diamines, the diamine is the low energy component in the monomer blend. As the diamine reacts, its concentration in the bulk decreases, the surface is improverished in surfactant, and the surface tension of the reactive system increases. A constant value is obtained when all the diamine monomer has been consumed. The final surface tension of a fully cured epoxy system without additive can be higher than any of the surface tensions of the initial reactants. But for rubber‐modified epoxy systems, the rubber is the component with the lowest surface energy, the surface properties of the reactive system are independent of the reaction time and very close to the surface properties of the rubber.

The effect of γ-Irradiation on the electrical properties of epoxy resin systems

The electrical properties, glass transition temperature, T g , and activation energy, E, of the MY750/HY956 epoxy system and the MY750/DDSA epoxy system have been systematically investigated before and after irradiation, after annealing and in other situations. The change in electrical properties of the system has been related to a two phase structure and the compounds contained in the epoxy systems. A monopole polarization has been suggested to explain the effect of the post-irradiation annealing for the MY750/HY956 epoxy system for temperatures T < T g .

Über die Synthese und das Verhalten von Polyoxypropylenglykol‐Diglycidäthern

AbstractPolyoxypropylene glycols with average molecular weights of 270, 425, 565, and 920 are converted by two different methods to the corresponding diglycidyl ethers. Polyoxypropylene glycol diglycidylethers (A) synthesized via chlorohydrin contain ClCH2 groups as a result of competition between the secondary hydroxyl groups of the poly‐oxypropylene glycol and those of the already formed chlorohydrin ethers in the presence of the epichlorohydrin. The formation of these ClCH2 groups consumes epichlorohydrin, thus causing a corresponding deficit of glycidyl groups. Treating the sodium alkoxides of the polyoxypropylene glycols with allyl bromide followed by epoxidizing the diallyl ethers with peracetic acid yields diglycidyl ethers (B), which contain acetyl groups Crosslinking mixtures from diglycidyl ether of bisphenol‐A and polyoxypropylene. glycol diglycidyl ethers A or B with diethylene triamine yields flexible epoxy resins. Properties of epoxy resin systems containing diglycidyl ethers A or B differ only slightly. By applying the theory of rubberlike elasticity the crosslinking density and thes hear modulus G of the flexible epoxy resins systems are calculated. The calculated shear moduli and those measured above the glass transition temperature are in relatively good agreement. Epoxy resin systems with none or a high content of flexibilizer show differences, which are caused by two effects.