Curing Reaction Of Epoxy Resin Research Articles

Kinetic approach for epoxy resins cured with diaminodiphenyl sulfone under non-isothermal conditions

The curing reactions of epoxy resin basing on diglycidyl ether bisphenol A (DGEBA) with 4,4′-diaminodiphenyl sulfone (DDS) were investigated with a differential scanning calorimeter and gel permeation chromatography. Based on the generating function method and the Monte Carlo simulation procedure, kinetic models for both isothermal and nonisothermal curing conditions were proposed. The apparent activation energy of curing reactions was found to be 14.9 Kcal/mol by the thermal analysis. According to our kinetic models, gel points, the profiles of epoxy conversion, and the molecular weights of polymers were calculated. Good agreement is obtained between the model predictions and experimental data. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 721–728, 1999

Core-shell particles designed for toughening the epoxy resins. II. Core-shell-particle-toughened epoxy resins

The diglycidyl ether of bisphenol A–m-phenylene diamine (DGEBA–MPDA) epoxy resin was toughened with various sizes and amounts of reactive core-shell particles (CSP) with butyl acrylate (BA) as a core and methyl methacrylate (MMA) copolymerized with various concentration of glycidyl methacrylate (GMA) as a shell. Ethylene glycol dimethacrylate (EGDMA) was used to crosslink either core or shell. Among the variables of incorporated CSP indicated above, the optimal design was to obtain the maximum plastic flow of epoxy matrix surrounding the cavitated CSP during the fracture test. It could be achieved by maximizing the content of GMA in a shell-crosslinked CSP, the particle size, and the content of CSP in the epoxy resin without causing the large-scale coagulations. The incorporation of reactive CSP could also accelerate the curing reaction of epoxy resins. Besides, it was able to increase the glass transition temperature of epoxy resins if the particle size ≤0.25 μm and the dispersion was globally uniform. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2313–2322, 1998

Properties of Glass-fibre Reinforced Epoxy Composites of Tetrafunctional Epoxy Resin

The curing reaction of epoxy resin l,l,2,2-tetrakis(4-glycidyloxyphenyl) ethane(TK-GOPE) with different aliphatic and aromatic amines has been studied by differential scanning calorimetry (DSC). The thermal stability of the cured products was also studied by thermogravimetric analysis (TGA). Using these data, different glass fibre reinforced epoxy composites were fabricated and their mechanical and electrical properties and their resistance to chemicals were studied. Activation energies of curing reactions is in the range of 80–187.27 KJ-mol−1. The cured products have good thermal stability, the composites have good mechanical strength, electrical insulation properties and chemical resistance.

Synthesis and thermal properties of combined liquid crystalline epoxy resins

Liquid crystalline epoxy resins were prepared by the curing reaction of epoxy and amine compounds with a mesogenic group in the mesomorphic temperature range. Some epoxy resins exhibited a typical liquid crystalline phase. Curing reaction of a mesogenic epoxy compound with an aliphatic amine compound containing cyano biphenyl group was faster than that of another epoxy resins confirmed by thermally controlled Fourier transform infrared measurements. The glass transition temperature of the liquid crystalline epoxy resin containing cyano biphenyl group increased with increasing curing reaction time. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1979–1990, 1998

Synthesis, by reactive extrusion, of high molar mass epoxy prepolymers containing rubber preformed particles

High molar mass epoxy prepolymers containing rubber dispersions based on carboxyl-terminated butadiene-acrylonitrile random copolymer (CTBN) were prepared from initially miscible solution of low molar mass epoxy prepolymers, bisphenol A and CTBN-based rubber. During chain extension inside a twin-screw extruder due to epoxy-phenoxy and epoxy-carboxy reactions, a phase separation process occurs. Epoxy-phenoxy and epoxy-carboxy reactions were catalyzed by the triphenyl phosphine. The effect of reaction parameters (temperature, catalyst, reactant stoechiometry) on the reactive extrusion process were analyzed. The structure of the prepolymers showed low branching reactions (2-5%). Low molar mass prepolymers have a Newtonian rheological behavior. Cloud-point temperature of different reactive liquid butadiene acrylonitrile random copolymer (RLP)/epoxy resin blends were measured for different RLP concentrations. It was shown that rubber particles remain insoluble in a range of temperature from room temperature to 180°C, typical of temperatures used for epoxy curing reactions. Prepolymers containing different rubber concentrations were cured using dicyandiamide as the hardener. The practical adhesion of the issued networks to an aluminium alloy increased with rubber concentration.

Radiofrequency (27.12 MHz) activation of the curing reaction of epoxy resins of DGEBA type

AbstractRadiofrequency (27.12 MHz) heating is used for the activation of the curing reaction of an epoxy resin of DGEBAa) type in presence of diaminodiphenylmethane as crosslinking agent. The principle of the activation process is based on the partial conversion as heat of the dielectric loss in the organic medium due to the forced dipolar relaxation at 27.12 MHz. The samples of thermosetting matter are positioned between two parallel steel plates or electrodes, and an electrical voltage is applied. When the temperature is sufficiently high, the step‐growth reactions starts working.

Synthesis of Photoreactive Imidazole Derivatives and Thermal Curing Reaction of Epoxy Resins Catalyzed by Photo-Generated Imidazole

Photoreactive blocked imidazoles such as N-(2-nitrobenzyloxycarbonyl)imidazole (2-NBCI), N-(3-nitrobenzyloxycarbonyl)imidazole (3-NBCI), N-(4-nitrobenzyloxycarbonyl)imidazole (4-NBCI), N-(4-chloro-2-nitrobenzyloxycarbonyl)imidazole (CNBCI), N-(5-methyl-2-nitrobenzyloxycarbonyl)imidazole (MNBCI), and N-(4,5-dimethoxy-2-nitrobenzyloxycarbonyl)imidazole (DNBCI) were synthesized in good yields by reactions of N,N′-carbonyldiimidazole (CDI) with corresponding benzyl alcohols. The prepared 2-NBCI decomposed smoothly to produce imidazole by UV-irradiation in tetrahydrofuran (THF) solution or poly(methyl methacrylate) (PMMA) film. Rates of photolysis of DNBCI, MNBCI and CNBCI were higher than that of 2-NBCI in PMMA film, although the rates of 3-NBCI and 4-NBCI were slower than that of 2-NBCI in PMMA film under the same conditions. Thermal curing reactions of epoxy resins and poly(glycidyl methacrylate-co-methyl methacrylate) [P(GMA55-MMA45)] using photo-generated imidazole were examined at 100–160°C. The ring opening reaction of epoxide groups, confirmed by IR spectra, in epoxy resins and P(GMA55-MMA45) proceeded smoothly by catalysis of the photo-generated imidazole.

Effect of mold heat transfer on the curing reaction of epoxy molding compound during transfer molding

The cyclic, transient heat transfer within a transfer molding tool during the EMC (Epoxy Molding Compound) curing stage was analyzed using iterative dual reciprocity boundary element method (DRBEM) and finite difference method (FDM) in a decoupled sequence. It is found that both heat transfer at the mold exterior surface and cyclic, transient variation in mold temperatures are significant and show distinguished influence on the extent of EMC curing. Compared with the presently analyzed results, the simulation based on an assumption of constant mold wall temperature overestimates the conversion profile, whereas the hybrid FESFM (Finite-Element/Shape-Factor Method) underpredicts it around the middle of the cavity surface where the exterior tool transfer effect is less distinguished. However, the FESFM also overestimates the conversion at locations near the mold parting surface where the influence from ambient heat transfer is significant.

Novel Thermal Curing Reactions of Epoxy Resin and Poly(glycidyl methacrylate) Using Photo-generated Difunctional Thiols

Novel Thermal Curing Reactions of Epoxy Resin and Poly(glycidyl methacrylate) Using Photo-generated Difunctional Thiols

Curing of Epoxy Resin with Styrene–Maleic Anhydride Copolymer: A Differential Scanning Calorimetric Investigation

Curing reactions of epoxy resin (EP-450) with stryene–maleic anhydride copolymer (St–MAn) samples are investigated by differential scanning calorimetry at a scan rate of 10 °C min−1 in an N2 atmosphere. The overall kinetic parameters of the curing reactions are estimated using Barrett as well as Freeman–Carroll methods based on a single dynamic scan. The curing reactions are found to follow overall first-order kinetics up to about 60–70% completion. Thermogravimetric analysis (TGA) of all the cured samples of epoxy resin (EP-450) with St–MAn copolymer samples has also been carried out at a heating rate of 10 °C min−1 in air.

Curing Properties of Matrix Epoxy Resin on Surface Modified Carbon Fibers

Changes in the curing properties of matrix epoxy resin and the dynamic viscoelastic properties of the composites have been studied for the purpose of research on the properties-change mechanism of composites depending on the surface modifed reinforcing fibers. The dynamic viscoelastic properties of the composites using the surface modified carbon fibers by photo-oxygenation were measured by torsional braid analysis (TBA). The curing properties using epoxy resin added with model reactants involving carboxyl or hydroxyl group were measured by differential scanning calorimetry (DSC) analysis. The obtained results are as follows.(1) The dynamic viscoelastic properties in curing of epoxy resin on carbon fibers were changed by photo-oxygenation. The Gr-onset temperatures, the gelation temperatures and the activation energies induced from TBA data were down. The glass transition temperatures after cure were up.These show that easy to react and well-progressed changes were induced by using the surface modified cabon fibers.(2) The hydroxyl group was superior to the carboxyl group in the promoting effect of epoxy curing reaction.

Study on curing reaction of epoxy resin modified with prepolymers containing spiro orthocarbonate

AbstractPrepolymers were prepared by the reaction of 3,9‐dihydroxyethyl‐3′9′‐dibenzyl‐1,5,7,11‐tetraoxaspiro(5,5)undecane with 4,4′‐diphenylmethane diisocyanate (MDI) and 1,6‐hexa‐methylene diisocyanate (HDI). The number‐average molecular weights of the prepolymers can be controlled by changing the mole ratios of spiro compound and diisocyanates. Kinetic studies of the cure reaction for the epoxy resin system modified with or without prepolymers were followed by a HLX‐1 dynamic torsional vibration apparatus. The results indicated that gel time (tg) and activation energy (Ea) increased as the content of prepolymers in the epoxy resin system increased. A difference with the cure reaction of the pure epoxy resin, the second‐order reaction for the epoxy resin modified with the prepolymers, was obtained. Rate constants (k) of the cure reaction are 0.231 min−1 for the epoxy resin, and 0.312 min−1 for the modified epoxy resin. The mechanism of the cure reaction was discussed. © 1995 John Wiley & Sons, Inc.

Photo-generation of Poly-functional Thiol and Thermal Curing Reaction of Epoxy Resins Using the Thiol

Photo-generation of Poly-functional Thiol and Thermal Curing Reaction of Epoxy Resins Using the Thiol

Photogeneration of polyfunctional amines and novel thermal curing reactions of epoxy resin and polyurethane oligomer using these amines

AbstractPhotochemical reactions of various blocked polyfunctional amines such as bis(4‐formylaminophenyl)methane (FAPM), bis(4‐acetylaminophenyl)methane (AAPM), bis(4‐benzoylaminophenyl)methane (BAPM), 2,4‐diformylaminotoluene (DFAT), m‐xylene diformamide, and bis[[(2‐nitrobenzyl)oxy]carbonyl]hexane‐1.6‐diamine were carried out to give the corresponding free amines in THF solution, in epoxy resin, or in polyurethane oligomer with terminal isocyanate groups. Photolysis of FAPM and DFAT to produce the corresponding polyfunctional amines such as 4,4'‐methylenedianiline and 2,4‐diaminotoluene proceeded with 80 and 75% conversions, respectively, in THF solution under UV irradiation at 5 h. AAPM and BAPM also produced the corresponding photo‐Fries rearrangement products with 32 and 38% conversions, respectively, under the same irradiation conditions. The photolysis of those compounds also occurred with similar conversions in the epoxy resin and in the polyurethane oligomer under UV irradiation; and the thermal curing reactions of the epoxy resin and the polyurethane oligomer with photogenerated polyfunctional amines proceeded smoothly after heating at 140°C for 2 hrs. © 1993 John Wiley & Sons, Inc.

The formation of composites from imidazolate polymer with epoxy resins

The chemical reaction of imidazole with metallic copper was studied by means of IR and XPS techniques. The product is bis-imidazolato-copper, which covers the surface in the form of a compact polymeric film. This reaction product can catalyze the curing reaction of epoxy resin at 450 K. The kinetics of the curing reaction was investigated with a model compound phenyl glycidyl ether (PGE). Measurement of the tensile shear strength shows that the adherence to epoxy resin of copper treated with azoles is stronger than the untreated ones.

Novel Thermal Curing Reactions of Epoxy Resin and Polyurethane Oligomers Using Photo-generated Poly-functional Amines

Novel Thermal Curing Reactions of Epoxy Resin and Polyurethane Oligomers Using Photo-generated Poly-functional Amines

Mounting of lead/acid battery positive-plate materials in epoxy matrices: an investigation of instances of excessive heating

Epoxy resins are often employed as the media for mounting lead/acid battery samples, as preparation for microscopic examination. Occasionally, it is found that the large quantities of heat, well in excess of those expected for normal epoxy curing reactions, are liberated during the mounting of sections of positive-plate material (mainly lead dioxide). This leads to the destruction of samples and creates a hazardous environment. In an initial study of the problem, the ambient temperature and the residual acid content of the plate material have been selected as the factors most likely to contribute to excessive heating. An investigation has shown that neither factor exerts a direct influence over the course of epoxy curing reactions. It appears, therefore, that instances of thermal runaway are determined by a complexity of parameters and laboratory procedures should take into account the possibility of such heating phenomena.

A model for the curing reaction of epoxy resins

Proposition de formule parametrique decrivant le durcissement de polymere reticulables et basee sur l'interdependance entre la vitesse de reaction et le temps de relaxation moleculaire, les variations de ce temps de relaxation etant decrites par analogie avec le recuit physique des verres. Un programme d'ordinateur permet la prediction des proprietes viscoelastiques des resines durcies. Application aux cas de resines epoxy derivees du bisphenol A

Vitrification effect on the curing reaction of epoxy resin

The curing reaction of diglycidyl ether of Bisphenol A(DGEBA) with triethylene tetramine(TETA) was studied by the differential scanning calorimetry(DSC). The reaction was affected as the vitrification occurred when the glass transition temperature(Tg) of the reaction mixture exceeded the curing temperature. In order to describe the curing reaction in the rubbery state as well as in the glassy state, the reaction kinetic equation containing the generalized WLF equation term was proposed and the parameters were determined from the DSC data.

Acceleration mechanisms in curing reactions involving model systems

AbstractThe mechanisms involving some of the most common accelerators in the curing reactions of epoxy resins have been investigated by use of model systems. Phenyl glycidyl ether was used as a model compound. The characterization of the reaction products was mainly carried out by High‐Performance‐Liquid‐Chromatography and by preparative methods. Special attention was paid to the oligomerization reactions of the oxirane ring in the presence of tertiary amines. Three different types of oligomers depending on phenyl glycidyl ethers are discussed. The mechanisms of multifunctional accelerators such as imidazoles or phenol‐MANNICH‐base‐compounds are much more difficult. The extraordinary interaction of imidazoles depends on the formation of different oligomers. Furthermore, the cleavage of the imidazole ring was observed. It is possible that the glycidyl ether oligomerization plays an important role in understanding the network structure. Some aspects of the accelerating effect of tertiary amines in the curing of glycidyl ethers with acid anhydrides were likewise discussed. The results obtained using these model reactions may be applied to influence the curing process in commercial epoxy resin systems.