Cationic polymerization behavior of β‐methylglycidyl ether derivatives and physical properties of their cationically cured materials

β‐Methylglycidyl ethers have been applied to Electrical and Electronic adhesives. However, there is no report about the detailed polymerization behavior and physical properties of their cured products. Hence, we investigated cationic polymerization behavior of bisphenol A di(β‐methylglycidyl) ether (Me‐BADGE) and physical properties of the cured products containing Me‐BADGE. DSC analysis suggested that Me‐BADGE could be cured completely at lower temperature than bisphenol A diglycidyl ether (BADGE). Physical properties were analyzed by dynamic viscoelastic analysis. Glass transition temperature (T_g) of BADGE homopolymer was 194°C. In contrast, the copolymer of BADGE (50 wt %) with Me‐BADGE (50 wt %) showed T_g at 124°C. According to the data of E’ and tan δ, crosslink density of the cured products decreased with increasing the Me‐BADGE content. The analysis of cationic polymerization of monofunctional β‐methylglycidyl ether suggested that the cationic polymerization proceeded not only through oxonium cation but also through carbocation formed by ring‐opening reaction of oxonium cation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42377.     

Comparative study of silicon‐containing cycloaliphatic epoxides between different chemical structures and curing mechanisms for potential light‐emitting diode encapsulation applications

The aim of this paper is to systematically investigate the curing behavior of three novel di‐ and trifunctional silicon‐containing cycloaliphatic epoxy resins by both anhydride and cationic ring‐opening polymerization methods as well as the viscoelasticity, thermal stability, water absorption and optical properties of the cured products. Differential scanning calorimetry curves show that, relative to anhydride curing, cationic polymerization can decrease the curing temperature to below 120 °C, and the reaction exothermic peaks become very narrow and sharp, exhibiting rapid curing characteristics at moderately low temperature. In addition, the differences between the anhydride and cationic curing methods bring about interesting variations in physical properties for the cured products which are well related to their chemical structures, polymerization mechanism, crosslinking density, segmental flexibility and inter‐segmental distance. The excellent transparency, rapid cationic curing rate, good thermal stability and high glass transition temperature of over 275 °C make this series of epoxy resins promising candidates for light‐emitting diode encapsulation applications. © 2012 Society of Chemical Industry     

Investigations of water and high energy radiation interactions in an epoxy

Differential scanning calorimetry (DSC) and infrared spectroscopy (IR) have been used to study the crosslinked epoxy system tetraglycidyl-4,4′-diaminodiphenyl methane cured with diaminodiphenyl sulfone. Samples cured at various temperatures were soaked in distilled water for extended periods or irradiated with 0.5 Me V electrons and ⁶⁰Co gamma. DSC results show that the standard-cured (137°C for 2 h and 160°C for 5 h) dry samples have a T_g around 190°C and a large exothermic reaction at about 260°C. The latter is attributed to further reaction of curing agent with the epoxide rings. The exothermic energy is about 124 cal/g for an uncured specimen, 42 cal/g for standard cured specimen, and 20 cal/g for soaked samples containing 4% H₂O. The exothermic energy is shown to decrease monotonically with the ionizing radiation dosage. IR results show a reduction in the intensity of the epoxide band as the exothermic energy is decreased.     

Thermal analysis of the styrene bulk polymerization and characterization of polystyrene initiated by two methods

Among the accidents caused by highly exothermic reactions, the proportion of polymerization thermal runaway accident accounts for about 48%. The mechanism of styrene polymerization in normal reaction process had been studied thoroughly in the literature. However, the interpretation of mechanism of runaway reactions was lacking. Based on the complicated mechanism of styrene polymerization by thermoinitiated and benzoyl peroxide (BPO) initiated. Differential scanning calorimeter and adiabatic rate calorimeter were devoted to analyze the thermal runaway processes of styrene polymerization. The initial exothermic temperature, adiabatic temperature rise, and maximum reaction temperature of BPO-initiated synthesis reaction were lower than those of thermoinitiated polymerization. Moreover, nuclear magnetic resonance imaging, gel permeation chromatography, and Fourier transform infrared spectrometry were used to characterize the polymerization products. The polystyrene initiated by the two methods had the same hydrogen structure, and BPO-initiated process included the effects of the thermoinitiated process. However, their molecular weight and distribution uniformity differed considerably. The free radicals produced by BPO decomposition participated in the chain reaction of styrene polymerization, accelerated instantaneous grain growth, and promoted the formation of short-chain polystyrene. In brief, the BPO-initiated polymerization process exhibited the desired thermal safety characteristics and gained product under thermal runaway was still polystyrene.     

Synthesis and properties of urethane elastomer-modified epoxy resin having hydroxymethyl group

Synthesis and properties of urethane elastomer-modified epoxy resins were studied. The urethane elastomer-modified epoxy resins were synthesized by the reaction of a 4-cresol type epoxy compound having hydroxymethyl groups (EPCDA) with isocyanate prepolymer. The structure was identified by IR, ¹H NMR and GPC. These epoxy resins (EPCDATDI) were mixed with a commercial epoxy resin (DGEBA) in various ratios. The mixed epoxy resins were cured with a mixture of 4,4′-diaminodiphenylmethane and 3-phenylenediamine (molar ratio 6:4) as a hardener. The curing behaviour of these epoxy resins was studied by DSC. The higher the concentration of EPCDATDI, the higher the onset temperature and the smaller the rate constant (k) of the exothermic cure reaction were. It was considered that the ratio of hydroxymethyl group to epoxide group was very small and the molecular weight of EPCDATDI was large. Therefore, the accelerating effect of the hydroxymethyl group on the epoxide–amine reaction was cancelled by the retardant effect of increased molecular weight and viscosity, and decreased molecular motion. Toughness was estimated by Izod impact strength and fracture toughness (K_1C). On addition of 10 wt% EPCDATDI with low molecular weight (M?_n 6710, estimated by GPC using polystyrene standard samples), Izod impact strength and K_1C increased by 70% and 60%, respectively, compared with unmodified epoxy resin. Glass transition temperatures (T_g) for the cured epoxy resins mixed with EPCDATDI measured by dynamic mechanical spectrometry were the same as those of unmodified epoxy resin. The storage modulus (E′) at room temperature decreased with increasing concentration of EPCDATDI. Toughness and dynamic mechnical behaviour of cured epoxy resin systems were studied based on the morphology.     

Glycidyl Azide Polymer Crosslinked Through Triazoles by Click Chemistry: Curing,Mechanical and Thermal Properties

Glycidyl azide polymer (GAP) was cured through “click chemistry” by reaction of the azide group with bispropargyl succinate (BPS) through a 1,3‐dipolar cycloaddition reaction to form 1,2,3‐triazole network. The properties of GAP‐based triazole networks are compared with the urethane cured GAP‐systems. The glass transition temperature (T_g), tensile strength, and modulus of the system increased with crosslink density, controlled by the azide to propargyl ratio. The triazole incorporation has a higher T_g in comparison to the GAP‐urethane system (T_g−20 °C) and the networks exhibit biphasic transitions at 61 and 88 °C. The triazole curing was studied using Differential Scanning Calorimetry (DSC) and the related kinetic parameters were helpful for predicting the cure profile at a given temperature. Density functional theory (DFT)‐based theoretical calculations implied marginal preference for 1,5‐addition over 1,4‐addition for the cycloaddition between azide and propargyl group. Thermogravimetic analysis (TG) showed better thermal stability for the GAP‐triazole and the mechanism of decomposition was elucidated using pyrolysis GC‐MS studies. The higher heat of exothermic decomposition of triazole adduct (418 kJ ⋅ mol⁻¹) against that of azide (317 kJ ⋅ mol⁻¹) and better mechanical properties of the GAP‐triazole renders it a better propellant binder than the GAP‐urethane system.     

A study on isothermal cure behavior of an epoxy-rich/anhydride system by differential scanning calorimetry

Cure behavior of a catalyzed epoxy/anhydride system was investigated for an epoxy-rich formulation using differential scanning calorimetry (DSC). The mixture was isothermally cured at different times and temperatures, and the cure behavior of the samples was analyzed by the peak exothermic temperature (T_peak) and the extent of cure reaction (X) from DSC thermograms. For the excess epoxy sample, two exothermic peaks at a low temperature from esterification reaction and at a high temperature from etherification on DSC curves appeared in the early stage of cure and shifted to a lower temperature scale with curing. However, the esterification peak disappeared and the remaining etherification peak shifted to a higher temperature with further cure. The shift of the peaks may be attributed to the change of reaction mechanism from kinetically controlled to diffusion-controlled. The extent of cure of esterification and etherification was also considered separately in this article. The result shows that esterification reaction mainly occurs in the early stage of cure and then etherification slowly proceeds after the completion of the esterification. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1101–1108, 1998     

Preparation and properties of high performance phthalide‐containing bismaleimide reinforced polydicyclopentadiene

A series of phenolphthalein‐containing bismaleimide (PPBMI) reinforced polydicyclopentadiene blends (PPBMI/polyDCPD) were prepared via the ring‐opening metathesis polymerization of DCPD in the presence of PPBMI. The crosslinked networks between PPBMI and polyDCPD backbones resulted in the reinforced structures. The curing behavior, thermal, and mechanical properties were investigated. Differential scanning calorimetry investigations showed the samples exhibit similar singular exothermic peak, and the exothermic peak of the PPBMI/polyDCPD blends slightly shifted to a lower temperature direction compared with the unfilled polyDCPD, meanwhile, the exothermic peak of the PPBMI/polyDCPD blends slightly shifts back to a higher temperature direction with the PPBMI content increased. Both dynamic mechanical analysis and thermo gravimetric analysis measurements revealed the optimal thermal performance of PPBMI/polyDCPD was obtained with 20 wt % loading of PPBMI. In addition, while PPBMI content increased, the weight loss peak at 100–200°C disappeared and the temperature of maximum rate of decomposition (T_d,max) increased. Moreover, bending tests showed the best mechanical performance was achieved at 5 wt % loading of PPBMI in blends. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40474.     

Synthesis of branched benzoxazine monomers with high molecular mass,wide processing window,and properties of corresponding polybenzoxazines

Four cyclotriphosphazene‐based benzoxazine monomers (I, II, III, and IV) with relatively high molecular weight were synthesized by a nucleophilic substitution reaction, and their chemical structures were confirmed by ¹H‐NMR and ³¹P‐NMR. A new term, oxazine value (OV, similar to epoxy value), was first proposed to explain the structure–property relationship of the cured polymers. The polymerization behaviors of the four monomers were studied by differential scanning calorimetry and Fourier transform infrared spectroscopy. The maximum exothermic peaks of the four monomers are in the range 244–248 °C. All monomers possess a wide processing window despite their high molecular weight. The thermal stability, glass‐transition temperature (T_g), and mechanical properties of each cured polymer were studied by thermogravimetric analysis and dynamic mechanical thermal analysis. The char yield at 850 °C, T_g, and storage moduli of PIV (polybenzoxazine obtained from monomer IV) are 60.0%, 218 °C, and 9.0 GPa, respectively. The surface property and humidity absorption character of the cured polybenzoxazines were also studied. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44453.     

Are 3‐D models necessary to simulate packed bed reactors? analysis and 3‐D simulations of adiabatic and cooled reactors

Simulations and analysis of transversal patterns in a homogeneous three‐dimensional (3‐D) model of adiabatic or cooled packed bed reactors (PBRs) catalyzing a first‐order exothermic reaction were presented. In the adiabatic case the simulation verify previous criteria, claiming the emergence of such patterns when (ΔT_ad/ΔT_m)/(Pe_C/Pe_T) surpasses a critical value larger than unity, where ΔT_ad and ΔT_m are adiabatic and maximal temperature rise, respectively. The reactor radius required for such patterns should be larger than a bifurcation value, calculated here from the linear analysis. With increasing radius new patterned branches, corresponding to eigenfunction of the problem emerge, whereas other branches become unstable. The maximal temperature of the 3‐D simulations may exceed the 1‐D prediction, which may affect design procedures. Cooled reactor may exhibit patterns, usually axisymmetric ones that can be characterized by two anomalies: the peak temperature may exceed the corresponding value of an adiabatic reactor and may increase with wall heat‐transfer coefficient, and the peak temperature in a sufficiently wide reactor need not lie at the center but rather on a ring away from it. In conclusions, we argue that transversal patterns are highly unlikely to emerge in practical adiabatic PBRs with a single exothermic reaction, as in practice Pe_C/Pe_T > 1. That eliminates patterns in stationary and downstream‐moving fronts, whereas patterns may emerge in upstream‐moving fronts, as shown here. This conclusion may not hold for microkinetic models, for which stationary modes may be established over a domain of parameters. This suggests that a 1‐D model may be sufficient to analyze a single reaction in an adiabatic reactor and a 2‐D axisymmetric model is sufficient for a cooled reactor. The predictions of a 2‐D cylindrical thin reactor with those of a 3‐D reactor were compared, to show many similarities but some notable differences. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Effects of water sorption at different temperatures on permanent changes in an epoxy

Crosslinked epoxy resins, tetraglycidyl 4,4′-diamino diphenyl methane cured with 4,4′-diamino diphenyl sulfone, were soaked in water at either 25°C or 70°C for varying lengths of time. The infrared spectra and DSC thermograms were obtained for samples that were soaked, or soaked and dried. There was a monotonic decrease in exothermic reaction energy with water content. The glass transition was also lowered, although samples soaked at 70°C showed a leveling in the T_g around 115°C. When the soaked samples were dried, the exothermic reaction energy showed near reversibility for samples soaked at 25°C while the 70°C samples were highly irreversible. IR of the latter samples showed that the 70°C water soaking resulted in reaction of some of the unreacted epoxide groups that remained after the initial cure.     

Synthesis of polymer materials by low energy electron beam. III. Effects of polymerization temperature in EB solid-state polymerization of semicrystalline urethane-acrylate film

In an electron beam (EB) polymerization of a urethane-acrylate prepolymer, the polymerization temperature greatly affected the structure and properties of the resulting gel film. Urethaneacrylate, which was synthesized by the reaction of poly(butylene adipate)diol, 4,4′-diphenylmethane diisocyanate, and 2-hydroxyethyl acrylate, was used as a prepolymer. The prepolymer was semicrystalline and showed a melting point in the region of 50–60°C. The maximum polymerization rate of the prepolymer was obtained when the prepolymer film was irradiated in the temperature range of 25–40°C. EB polymerization below the melting point (T_m) of the prepolymer produced semicrystalline polyurethane-acrylate gel films with a spherulitic texture. On the other hand, EB polymerization above the T_m destroyed the crystalline phase of the prepolymer to give transparent gel films. The gel film cured below the T_m had higher stress at yield, Young's modulus, and tensile strength than those cured above the T_m. Such temperature effects are attributed to whether or not the EB polymerization proceeds with retention of crystalline structure of the prepolymer.     

Curing kinetics and thermal properties of vinyl ester resins

The curing kinetics of dimethacrylate-based vinyl ester resins were studied by scanning and isothermal DSC, gel time studies, and by DMTA. The rate of polymerization was raised by increased methyl ethyl ketone peroxide (MEKP) concentration but the cocatalyst, cobalt octoate, retarded the reaction rate, except at very low concentrations. By contrast, the gel time was reduced for all increases in either peroxide or cobalt concentration. This contradictory behavior was explained by a kinetic scheme in which the cobalt species play a dual role of catalyzing the formation of radicals from MEKP and of destroying the primary and polymeric radicals. The scanning DSC curves exhibited multiple peaks as observed by other workers, but in the present work, these peaks were attributed to the individual influence of temperature on each of fundamental reaction steps in the free radical polymerization. Physical aging appeared to occur during the isothermal polymerization of samples cured below the “fully cured” glass transition temperature (T_g). For these undercured materials, the difference between the DSC T_g and the isothermal curing temperature was approximately 11°C. Dynamic mechanical analysis of a partially cured sample exhibited anomalous behavior caused by the reinitiation of cure of the sample during the DMTA experiment. For partially cured resins, the DSC T_g increased monotonically with the degree of cure, and this dependence was fitted to an equation related to the Couchman and DiBenedetto equations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 769–781, 1997     

Mn+Sb2O3 Thermite/Intermetallic Delay Compositions

The binary Mn+Sb₂O₃ pyrotechnic composition was investigated for mining detonator time delay applications. EKVI thermodynamic modelling predicted two maxima in the adiabatic reaction temperature. The local maximum, at a manganese fuel content of ca. 36 wt‐%, corresponds to a pure thermite‐type redox reaction: 3 Mn+Sb₂O₃→3 MnO+2Sb. The overall maximum in the adiabatic reaction temperature (ca. 1640 K), at the fuel‐rich composition of 49 wt‐% Mn, is consistent with the reaction 5 Mn+Sb₂O₃→3 MnO+2 MnSb, i.e. a combination of the standard thermite with an additional exothermic intermetallic reaction. XRD analysis of combustion residues confirmed the formation of MnSb and Mn₂Sb for fuel‐rich compositions. Burn rates were measured using delay elements assembled into commercial detonators. The d₅₀ particle sizes were 23.4 and 0.92 μm for the Mn fuel and Sb₂O₃ oxidant powders, respectively. The delay elements comprised rolled lead tubes with a length of 44 mm and an outer diameter of 6.4 mm. The rolling action compacted the pyrotechnic compositions to 74 ± 2 % theoretical maximum density. The burning rate increased linearly from 4.2 to 9.4 mm s⁻¹ over the composition range 25–50 wt‐% Mn.     

Thermosetting foam with a high bio‐based content from acrylated epoxidized soybean oil and carbon dioxide

A resilient, thermosetting foam system with a bio‐based content of 96 wt % (resulting in 81% of C₁₄) was successfully developed. We implemented a pressurized carbon dioxide foaming process that produces polymeric foams from acrylated epoxidized soybean oil (AESO). A study of the cell dynamics of uncured CO₂/ AESO foams proved useful to optimize cure conditions. During collapse, the foam's bulk density increased linearly with time, and the cell size and cell density exhibited power‐law degradation rates. Also, low temperature foaming and cure (i.e. high viscosity) are desirable to minimize foam cell degradation. The AESO was cured with a free‐radical initiator (tert‐butyl peroxy‐2‐ethyl hexanoate, T_i ～ 60°C). Cobalt naphtenate was used as an accelerator to promote quick foam cure at lower temperature (40–50°C). The foam's density was controlled by the carbon dioxide pressure inside the reactor and by the vacuum applied during cure. The viscosity increased linearly during polymerization. The viscosity was proportional to the extent of reaction before gelation, and the cured foam's structure showed a dependence on the time of vacuum application. The average cell size increased and the cell density decreased with foam expansion at a low extent of cure; however, the foam expansion became limited and unhomogeneous with advanced reaction. When vacuum was applied at an intermediate viscosity, samples with densities ～ 0.25 g/cm³ were obtained with small (<1 mm) homogeneous cells. The mechanical properties were promising, with a compressive strength of ～ 1 MPa and a compressive modulus of ～ 20 MPa. The new foams are biocompatible. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and properties of UV-autocurable BTDA-based epoxy-multiacrylate resins. Effects of the degree of polymerization and the epoxy type

A series of UV-autocurable epoxy-multiacrylate resins was synthesized, and the effects of degree of polymerization (DP) and epoxy type on their properties were investigated. These autocurable multiacrylate resins possess good pot life and are cured rapidly when exposed to ultraviolet (UV) without the addition of photoinitiator or photosensitizer. The curing rate of the autocurable resins was probably dependent on the number of abstractable hydrogen in epoxy resins. Stress-strain, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) were used to characterize the properties of cured multiacrylate resins. Increased crosslinking density of cured films improved tensile properties. Increasing the molar ratio of epoxy resin in the multiacrylate resins was found to decrease the effective acrylate concentration of resins and to depress crosslinking density of cured resins, which also resulted in an increased elongation at break but a decreased Young's modulus and breaking strength. Furthermore, the different structures of epoxy resins were used to give wide range properties of cured epoxy-multiacrylate resins with a glass transition temperature (T_g range from 74 to 102°C. The film properties of the multiacrylate resins coated on steel plates were also investigated.     

Precipitation polymerization of PLGA with Sn(Oct)2/BuOH in supercritical carbon dioxide

In order to increase molecular weight of PLGA, BuOH was introduced as a co‐initiator to Sn(Oct)₂ in ring‐opening precipitation polymerization of L ‐lactide and glycolide in supercritical carbon dioxide (ScCO₂). The polymerization mechanism of the reaction processes on Sn(Oct)₂ with BuOH was explored. The positive effect of BuOH on polymer molecular weight was studied. PLGA with higher M_w (of 19,500 g/mol) and narrower PDI (of 1.12) was successfully prepared by ring‐opening precipitation polymerization in ScCO₂ using Sn(Oct)₂/BuOH as an efficient catalytic system. Influence of reaction conditions, such as monomer feed concentration, reaction temperature, pressure, and time, were also investigated in detail. POLYM. ENG. SCI., 54:704–710, 2014. © 2013 Society of Plastics Engineers     

Kinetic studies of the polymerization of nylon-6 block copolymers

The kinetics of the activated anionic polymerization of caprolactam to nylon-6 and its copolymers has been studied. Nylon-6 block copolymer and nylon-6 were prepared at various initial reaction temperatures (140°C to 165°C) by anionic polymerization in an adiabatic dewar flask. Different concentrations of poly(ethylene oxide) (PEO) in 4,4′-diphenyl methane diisocyanate (MDI)-capped PEO and 1 mole percent MDI, in a caprolactam solution, were used as the activators with the catalyst, the sodium salt of caprolactam. The kinetics of the reaction were analyzed from an adiabatic temperature rise. A new method was applied to determine the rate parameters. The activation energy, E_a, of nylon-6 and nylon-6 block copolymers were found to be 22 kcal/mole. The collision frequency factor, A_o, steadily decreased and the autocatalytic constant, B_o, decreased to a constant value of 16 with the introduction of PEO. However, it was found that the order of reaction, n, was almost a constant value at the second order for all experiments.     

Synthesis of poly(vinyl acetate) by degenerative transfer polymerization in the presence of iodine

A new curing agent containing maleimide and biphenyl moieties (MIBP) was synthesized by the condensation polymerization of 4,4′-bismethoxymethylbiphenyl and N-(4-hydroxyphenyl)maleimide (HPM). The chemical structure was characterized with Fourier transform infrared (FTIR) spectroscopy, and the molecular weight of the new curing agent was determined by gel permeation chromatography. Curing reactions of O-cresol formaldehyde epoxy (CNE) resin with MIBP were investigated under nonisothermal differential scanning calorimetry, and the exotherm exhibited two overlapping exothermic peaks during the curing process; this was demonstrated by FTIR traces. The Flynn–Wall–Ozawa and Friedman methods were used to examine the kinetic parameters and the kinetic models of the curing processes of the CNE/MIBP mixtures. Both reactions turned out to be nth-order curing mechanisms. Values of the reaction order (n) = 1.42 and activation energy (E_a) = 91.2 kJ/mol were obtained for the first reaction of the curing of the CNE/MIBP system, and values of n = 1.11 and E_a = 78.7 kJ/mol were obtained for the second reaction. The thermal properties of the cured resin were measured with thermogravimetric analysis, and the results show a high glass-transition temperature (T_g = 155°C), good thermal stability (temperature at 10% weight loss, under nitrogen and in air, ≈ 400 and 408°C, respectively), and high char yield (temperature = 800°C, char residue = 44.5% under nitrogen). These excellent thermal properties were due to the introduction of the maleimide and biphenyl groups of MIBP into the polymer structure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Curing of epoxy systems at sub‐glass transition temperature

Three epoxy‐amine thermoset systems were cured at a low ambient temperature. Evolution of the reaction kinetics and molecular structure during cure at the sub‐glass transition temperature was followed by DSC and chemorheology experiments. The effect of vitrification and the reaction exotherm on curing and final mechanical properties of the epoxy thermosets was determined. Thermomechanical properties of the low‐temperature cured systems depend on the reaction kinetics and volume of the reaction mixture. Curing of the fast‐reacting system in a large volume (12‐mm thick layer) resulted in the material with T_g exceeding the cure temperature by 70–80°C because of an exothermal temperature rise. However, the reaction in a too large volume (50‐mm layer) led to thermal degradation of the network. In contrast, thin layers (1.5 mm) were severely undercured. Well‐cured epoxy thermosets could be prepared at sub‐T_g temperatures by optimizing reaction conditions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3669–3676, 2006