Curing mechanism and thermal properties of epoxy-imidazole systems

Heise, Martin; Martin, G. C.

doi:10.1021/ma00191a020

Cited by 178 publications

(142 citation statements)

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“…However, for the 1-substituted imidazoles, the OH-adduct reaction did not occur; only the O¯-adduct reaction occurred through 3-N with the epoxide ring without similar shoulder. Regrettably, Heise and Martin [21] did not explain why OH-adduct reaction could form a shoulder and O¯ adduct reaction could not form a shoulder. These observations were consistent with the results of Ooi et al [4].…”

Section: Non-isothermal Reactions Of Den/hmmm/emi-24 and Mden/hmmmmentioning

confidence: 97%

“…Generally, imidazole with low content was used to catalyze and study the etherification. Heise and Martin [21] found that the -OH-adduct reaction occurred only for 1-unsubstituted imidazoleles (such as EMI-24) with a shoulder on the main exothermic peak at low EMI-24 concentrations. However, for the 1-substituted imidazoles, the OH-adduct reaction did not occur; only the O¯-adduct reaction occurred through 3-N with the epoxide ring without similar shoulder.…”

Section: Non-isothermal Reactions Of Den/hmmm/emi-24 and Mden/hmmmmentioning

confidence: 99%

“…While in MDEN/HMMM system, the -OH decreased over time, and the higher curing temperature improved the conversion rate of reactive groups. [7,21,22,38], the mechanisms of DEN/HMMM/EMI-24 and MDEN/HMMM were proposed as shown in Figures 8 and 9. From Figure 8, it could be seen that the transformation of proton can afford the acidic environment to assist the reaction between DEN and HMMM.…”

Section: Isothermal Ftir Analysismentioning

confidence: 99%

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Curing kinetics, mechanism and chemorheological behavior of methanol etherified amino/novolac epoxy systems

Zhao¹,

Zhang²,

Sun³

et al. 2014

Express Polym. Lett.

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Abstract. The curing kinetics and mechanism of epoxy novolac resin (DEN) and modified epoxy novolac resin (MDEN) with methanol etherified amino resin were studied by means of differential scanning calorimetry (DSC), Fourier transforminfrared (FT-IR) spectroscopy and chemorheological analysis. Their kinetics parameters and models of the curing were examined utilizing isoconversional methods, Flynn-Wall-Ozawa and Friedman methods. For the DEN mixture, its average activation energy (E a ) was 71.05 kJ/mol and the autocatalytic model was established to describe the curing reaction. The MDEN mixture exhibited three dominant curing processes, termed as reaction 1, reaction 2 and reaction 3; and their E a were 70.05, 106.55 and 101.91 kJ/mol, respectively. Besides, E a of reaction 1 was similar to that of DEN mixture, while E a of reactions 2 and 3 corresponded to that of the etherification reaction between hydroxyl and epoxide group. Moreover, these three dominant reactions were n th order in nature. Furthermore, their curing mechanisms were proposed from the results of DSC and FTIR. The chemorheological behavior was also investigated to obtain better plastics products via optimizing the processing schedules.

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Section: Non-isothermal Reactions Of Den/hmmm/emi-24 and Mden/hmmmmentioning

confidence: 97%

Section: Non-isothermal Reactions Of Den/hmmm/emi-24 and Mden/hmmmmentioning

confidence: 99%

Section: Isothermal Ftir Analysismentioning

confidence: 99%

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Curing kinetics, mechanism and chemorheological behavior of methanol etherified amino/novolac epoxy systems

Zhao¹,

Zhang²,

Sun³

et al. 2014

Express Polym. Lett.

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“…The kinetics of imidazole/resin systems has been widely studied by using isothermal or dynamic DSC technique. [1][2][3][4][5] But their studies were all based on the assumption of a constant E and the whole reaction of curing was considered as a single kinetic process (Method I). Therefore, the calculated E is the apparent activation energy of the global reaction.…”

mentioning

confidence: 99%

Mechanism and Kinetics of Epoxy-Imidazole Cure Studied with Two Kinetic Methods

Zhou

Jin

et al. 2005

Polym J

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ABSTRACT:Curing kinetics and mechanism of the diglycidyl ether of bisphenol-A (DGEBA) initiated with 2-ethyl-4-methylimidazole (EMI-2,4) were studied with two methods by using differential scanning calorimetry (DSC). Method I and Method II were deduced by assuming a constant E and a variable E, respectively. With Method I, the cure reaction activation energy E, the frequency factor A and the overall order of reaction m þ n are calculated to be 49.03 KJ mol À1 , e 14:5 and 1.22, respectively. With Method II, E is proved to decrease initially, and then increase as the cure reaction proceeds, and the value of E spans from 34.3 to 63.84 KJ mol À1 . The variations of E were also used to study the cure reaction mechanism. Method I and Method II are effective as long as they are used in proper aspects. With these two methods used all together, we can have a comprehensive and in-depth understanding of the cure reactions, such as those of the DGEBA/EMI-2,4 system. [DOI 10.1295/polymj.37.833] KEY WORDS Cure Reaction / DSC / Kinetic Method / DGEBA/EMI-2,4 System / Imidazole-cured resins are widely used in the electronics industry as molding and sealing compounds because they exhibit a better heat resistance, a higher modulus, and a wider range of cure temperatures than amine-cured systems. The kinetics of imidazole/resin systems has been widely studied by using isothermal or dynamic DSC technique. [1][2][3][4][5] But their studies were all based on the assumption of a constant E and the whole reaction of curing was considered as a single kinetic process (Method I). Therefore, the calculated E is the apparent activation energy of the global reaction. However, the reaction of curing epoxy resins is normally very complex, such as the change from chemical kinetic control to diffusion control in the advance of the curing, 6,7 and E changed momently. In this work, another method deduced without the assumption of constant E (Method II) was also employed to analyze the dynamic DSC data, then the interpretation of the dependence of E on the extent of reaction in the terms of the reaction mechanisms was also made. As a result, with these two different kinetic methods, which have their particular merits and demerits, used together, we can have a comprehensive and in-depth understanding of the curing kinetics of the DGEBA/EMI-2,4 system. EXPERIMENTALEpoxy resin used in this work was a nominally difunctional epoxy resin, Epon 828 supplied by Shanghai Resin Co. Epon 828 is, basically, DGEBA with the epoxy value of 0.48-0.52 mol/100 g. The structure for DGEBA is shown in Figure 1. The curing agent used was EMI-2,4 supplied by Beijing Chemical Reagent Co. Other agents used were analytically pure grade and were supplied by Beijing Chemical Reagent Co.Approximately 10 mg sample of the mixture of DGEBA and EMI-2,4 was weighed accurately into an aluminum DSC sample pan and then covered with an aluminum lid. The entire operation was carried out in a dry chamber. DSC measurements were carried out by using a Perkin-Elmer DSC-7 system. The DSC ...

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“…Assuming that the organic phase consists mainly of homopolymerized DGEBA, this is a rather low value in comparison with those reported in the literature. 30,31 One must take into account that, during the solgel process, the sample is exposed to a highly humid environment, and that ethanol and water are released by the hydrolysis and condensation of ethoxysilyl groups. Both ethanol and water can participate in the anionic homopolymerization of DGEBA as chain-transfer agents, reducing the crosslinking density and consequently the T g .…”

Section: Thermal Characterizationmentioning

confidence: 99%

Hybrid epoxy networks from ethoxysilyl-modified hyperbranched poly(ethyleneimine) and inorganic reactive precursors

Acebo

Fernández‐Francos

Santos³

et al. 2015

European Polymer Journal

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New epoxy-silica hybrid coatings were prepared by a dual process consisting of a sol-gel process using tetraethoxysilane (TEOS) or 3-glycidyloxypropyl trimethoxysilane (GPTMS) in the presence of hyperbranched poly(ethyleneimine) with ethoxysilyl groups at the chain ends (PEI-Si) followed by a homopolymerization of diglycidylether of bisphenol A (DGEBA) using 1-methylimidazole (1-MI) as anionic initiator. The influence of the amount of TEOS and GPTMS in the characteristics of the coating was examined. Thin transparent films were obtained and their morphology was observed by transmission electron microscopy (TEM). The hydrolytic condensation was confirmed by 29Si-NMR studies. Cage-like nanometric structures were formed in case of adding GPTMS and bigger silica particles on adding TEOS to the formulation. Thermal stability was evaluated by thermogravimetry and the scratch resistance properties were also investigated, showing an improvement in resistance to break and to detachment in all the coatings containing GPTMS. Polymer Journal as you recommended us.As you mentioned in your decision letter the main remark is that the novelty has not been stressed sufficiently. However, the general comments of the reviewers were not bad.We recognized that the redaction did not include the novelty until we reach the discussion part and therefore we have included in the new version your opinion and we have stressed the novelty achieved in our work from the beginning. We have also included some changes suggested by the reviewers. Thus, we hope you can go further with the acceptance of our paper in European Polymer Journal.Looking forward to hearing from you, I remain. Cover LetterComments to the reviewers.Reviewer #1: Graphical abstract:It is not clear what the authors want to transmit in the graphical abstract. The paper is not directly addressing the application procedure of the coatings. The graphical abstract should be adapted to show more clearly the real work addressed in this paper. We have changed completely the graphical abstracts and we hope that the new version clearly represent the work contained in the article HighlightsThe highlights do not reflect the main findings / advances in this paper. They should be rewritten to show the key findings / novelty. We have also changed and stressed the key findings AbstractThe abstract needs to be revised. Does the TEOS / GPTMS affect the properties of the hyperbranched polymer? So yes, in which direction? The abstract should be more indicative of what the reader will find in the paper. The abstract has been rewritten. The addition of TEOS does not affect the properties of the hyperbranched polymer, but the properties of the final hybrid thermoset. The addition of TEOS leads to the formation of bigger particles, quite different from the cage-like particles formed from PEI-Si and/or GPTMS. The addition of GPTMS produces an improvement in resistance to break and to detachment in all the coatings. The incorporation of GPTMS to TEOS containing formulations allowed to prepar...

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Curing mechanism and thermal properties of epoxy-imidazole systems

Cited by 178 publications

References 3 publications

Curing kinetics, mechanism and chemorheological behavior of methanol etherified amino/novolac epoxy systems

Curing kinetics, mechanism and chemorheological behavior of methanol etherified amino/novolac epoxy systems

Mechanism and Kinetics of Epoxy-Imidazole Cure Studied with Two Kinetic Methods

Hybrid epoxy networks from ethoxysilyl-modified hyperbranched poly(ethyleneimine) and inorganic reactive precursors

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