Kinetic regimes in the curing process of epoxy-phenol composites

Granado, Lérys; Kempa, Stefan; Gregoriades, Laurence J.; Brüning, Frank; Genix, Anne-Caroline; Fréty, Nicole; Anglaret, Éric

doi:10.1016/j.tca.2018.07.019

Cited by 30 publications

(24 citation statements)

References 53 publications

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“…The glass transition temperature can be correlated to the extent of conversion according to the Di Benedetto equation [57,58,59]:Tg−Tg0Tg∞−Tg0=λα[1−(1−λ)α] with λ given by:λ=Δcp∞Δcp0 where Tg0 is the value for α = 0, corresponding to the T g of the unreacted system, Tg∞ is the “infinite” T g corresponding to the maximum value that can be obtained, ideally the value for α = 1 and λ is a fitting parameter, which was found to be equal to 0.30 by the nonlinear fitting. This value is close to what was previously observed for other thermosetting systems [60]. This parameter was obtained by DSC measurement from the ratio of Δ c p of the glass transition of the fully cured system (Δ C p ∞ ) divided by the Δ c p of the glass transition of uncured system (Δ c p 0 ).…”

Section: Resultssupporting

confidence: 88%

Kinetics and Chemorheological Analysis of Cross-Linking Reactions in Humins

et al. 2019

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Humins is a biomass-derived material, co-product of the acid-catalyzed conversion of cellulose and hemicellulose to platform chemicals. This work presents a thorough study concerning the crosslinking kinetics of humins by chemorheological analysis and model-free kinetics under isothermal and non-isothermal curing. Humins can auto-crosslink under the effect of temperature, and the reaction can be fastener when adding an acidic initiator. Thus, the effect of P-Toluenesulfonic acid monohydrate (pTSA) on the crosslinking kinetics was also studied. The dependencies of the effective activation energy (Eα-dependencies) were determined by an advanced isoconversional method and correlated with the variation of complex viscosity during curing. It is shown that humins curing involves multi-step complex reactions and that the use of an acidic initiator allows faster crosslinking at lower temperatures, involving lower Eα. The shift from chemical to diffusion control was also estimated.

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Section: Resultssupporting

confidence: 88%

Kinetics and Chemorheological Analysis of Cross-Linking Reactions in Humins

et al. 2019

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“…31 However, the mechanistic explanation based on vitrification/gelation contribution to the activation energy were not satisfactory, in our sense. Indeed, in our case, we notice the absence of the diffusion contribution to the activation energy (which usually tend to significantly higher E with increasing α, in comparison, for instance, to epoxy cured PF novolac) 36 . The reactive sites are located on short monomers in the case of phenolic resins, therefore the polymer network does not hinder the curing kinetics with additional diffusion barriers.…”

Section: Thermo-kinetics Of Curingmentioning

confidence: 44%

Catalysis for highly thermostable phenol-terephthalaldehyde polymer networks

Granado

Tavernier

Foyer

et al. 2020

Chemical Engineering Journal

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There is a crucial need to eliminate formaldehyde (F) from high-performance thermoset formulations. We propose herein the study of innovative phenol (P)-terephthalaldehyde (TPA) resole, synthesized under basic conditions. For aerospace applications, alkali-or alkaline-earth-based catalysts should be avoided because they degrade the polymer performances in real conditions. To address this issue, we successfully employed DBU to catalyze the resole formation and compared the mechanisms and performances to the usual NaOH-catalyzed formulation. Insights into the undergoing chemical reactions of crosslinking were given by IR and NMR spectroscopies together with thermal analyses (DSC and TGA). We proposed a two-step mechanism pathway, directly arising from the multiple reactions occurring with TPA (compare to only two with F). An in-depth thermo-kinetics study was efficient to compare both NaOH and DBU catalyzed reactions (performed using multiple heating rates DSC data and isoconversional computational method of Vyazovkin). Finally, TGA results showed that these new resoles presented increased thermal performances compare to commercial PF. TOC This paper presents innovative and highly-performant phenol-terephthalaldehyde thermosets and gives insights into the catalysis and mechanisms of polymerization.

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“…Typically, this is done offline using methods such as dynamic scanning calorimetry (DSC) in combination with iso-conversional kinetic analysis [12][13][14][15][16][17][18][19][20][21]. DSC has proven to be a powerful tool in the characterization of the curing kinetics of numerous thermosetting materials [11,[22][23][24]. Although DSC is very well suited for generating kinetic models, it holds several disadvantages.…”

Section: Introductionmentioning

confidence: 99%

Cure Kinetics Modeling of a High Glass Transition Temperature Epoxy Molding Compound (EMC) Based on Inline Dielectric Analysis

et al. 2021

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We report on the cure characterization, based on inline monitoring of the dielectric parameters, of a commercially available epoxy phenol resin molding compound with a high glass transition temperature (>195 °C), which is suitable for the direct packaging of electronic components. The resin was cured under isothermal temperatures close to general process conditions (165–185 °C). The material conversion was determined by measuring the ion viscosity. The change of the ion viscosity as a function of time and temperature was used to characterize the cross-linking behavior, following two separate approaches (model based and isoconversional). The determined kinetic parameters are in good agreement with those reported in the literature for EMCs and lead to accurate cure predictions under process-near conditions. Furthermore, the kinetic models based on dielectric analysis (DEA) were compared with standard offline differential scanning calorimetry (DSC) models, which were based on dynamic measurements. Many of the determined kinetic parameters had similar values for the different approaches. Major deviations were found for the parameters linked to the end of the reaction where vitrification phenomena occur under process-related conditions. The glass transition temperature of the inline molded parts was determined via thermomechanical analysis (TMA) to confirm the vitrification effect. The similarities and differences between the resulting kinetics models of the two different measurement techniques are presented and it is shown how dielectric analysis can be of high relevance for the characterization of the curing reaction under conditions close to series production.

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Kinetic regimes in the curing process of epoxy-phenol composites

Cited by 30 publications

References 53 publications

Kinetics and Chemorheological Analysis of Cross-Linking Reactions in Humins

Kinetics and Chemorheological Analysis of Cross-Linking Reactions in Humins

Catalysis for highly thermostable phenol-terephthalaldehyde polymer networks

Cure Kinetics Modeling of a High Glass Transition Temperature Epoxy Molding Compound (EMC) Based on Inline Dielectric Analysis

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