Mechanical relaxation spectroscopy of three triepoxide-based polymers

Wasylyshyn, D. A.; Johari, G. P.

doi:10.1002/(sici)1099-0488(19991101)37:21<3071::aid-polb16>3.0.co;2-a

Cited by 9 publications

(1 citation statement)

References 31 publications

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“…There are different ways to estimate this parameter including analysis of NMR, FTIR, or Raman spectra. − Nevertheless, it should be noted that in the case of step growth polymerization of DGEBA with different hardeners the calorimetry technique seems to be the most suitable tool to evaluate α. Applying the standard procedure described in the literature, − we performed additional nonisothermal DSC measurements and estimated the degree of monomer conversion according to the following equation: where α DSC is the conversion determined from DSC measurements, Δ H (iso) is the enthalpy change as a function of the polymerization time at given temperature (isothermal measurements), and Δ H total is the total heat of the reaction.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Polymerization Rate and Conductivity of Ionic Liquid-Based Epoxy Resin

et al. 2017

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The kinetics of polymerization of Bisphenol-A diglycidyl ether (DGEBA), a well-known epoxy resin, with two ionic amines 1-(3-aminopropyl)-3-butylimidazolium bis(trifluoromethylsulfonyl)imide ([apbim][NTf2]) and the tetrabutylammonium leucine ([N4444][Leu]) have been studied with the use of differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS) at various temperatures. We found many fundamental differences between the progress of this reaction with respect to the classical system (curing of epoxy resin with ordinary nonconducting hardeners). One of the most significant differences is related to the mechanism of polymerization. It is worthwhile to mention that usually the autocatalytic model is used to describe the curing of DGEBA with ordinary amines. However, herein, the kinetic curves followed a clearly exponential shape characteristic of first-order kinetics. We claim that the change in mechanism of polymerization is related to the presence of a conducting amine that acts as both the substrate and the catalyst of this specific chemical conversion. Also, it is presented that the pace of the reaction only weakly depends on temperature, which is reflected in the relatively low activation energy. On the other hand, the degree of monomer conversion stays around 45%–70% as typically reported for the polymerization of DGEBA with nonconducting hardeners. In addition, we measured the time evolution of dc conductivity as the reaction proceeded and observed that a change in this parameter correlates very well with the monomer conversion in contrast to the reaction of nonconducting systems. Finally, ionic conductivity of the resulted cured samples was investigated and found to be quite significant at the glass transition temperature with respect to other polymerized ionic liquids.

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Section: Resultsmentioning

confidence: 99%

Enhanced Polymerization Rate and Conductivity of Ionic Liquid-Based Epoxy Resin

et al. 2017

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Determination of the molecular weight between cross‐links for different ambers: Viscoelastic measurements of the rubbery plateau*

Kong

Meng

McKenna

2022

Polymer Engineering & Sci

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While much is known about the chemistry of amber, there are, to our knowledge, no quantitative estimates of the molecular weight between cross-links or quantitative estimates of the amount of cross-linking. In the present study we provide new data that advances our understanding of ancient ambers through an investigation of the network structure based on measurements of the rubbery modulus. Then, using rubber elasticity theory, we provide semiquantitative insights into the network structure. The work provides direct mechanical evidence of the chemically cross-linked structure of a Burmese amber, a Dominican amber, a Fushun amber, and two Baltic ambers by quantifying the molecular weight between cross-links M c . The values of M c of the studied ambers ranges from 1800 to 3000 g/mol, and the number of monomers between two cross-link junctions is estimated to be between 6 and 10.

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