| Titre : |
Assessment of relative reactivities and kinetics of various polyamine and polyamide hardeners with epoxy resins for designing high performance epoxy coatings using differential scanning calorimetry |
| Type de document : |
texte imprimé |
| Auteurs : |
Girish Mirchandani, Auteur |
| Année de publication : |
2007 |
| Article en page(s) : |
p. 69-92 |
| Note générale : |
Bibliogr. |
| Langues : |
Anglais (eng) |
| Catégories : |
Analyse thermique
Calorimétrie
Epoxydes
PolyamidesUn polyamide est un polymère contenant des fonctions amides -C(=O)-NH- résultant d'une réaction de polycondensation entre les fonctions acide carboxylique et amine.
Selon la composition de leur chaîne squelettique, les polyamides sont classés en aliphatiques, semi-aromatiques et aromatiques. Selon le type d'unités répétitives, les polyamides peuvent être des homopolymères ou des copolymères.
Polyamines
Réticulants
Réticulation (polymérisation)
Revêtements:Peinture
|
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
High performance epoxy coatings have to be designed correctly in order to give corrosion protection in hostile environmental conditions. There needs to be a scientific method to accurately determine the reactivity of complex hardeners or a mixture of different hardeners in order to compare them with existing systems and select the correct curing agent for a given epoxy resin. While it may be easy to predict the reactivity of simple hardeners (short chain polyamines) of known chemical structures, the same is not possible for proprietary hardeners of unknown structures. The selection of hardener on the basis of amine value and certain theoretical rules is a misnomer and actual working conditions such as steric hindrance and catalytic effects need to be taken into account. The aim of this paper is to investigate and quantify the relative reactivities of different hardeners and study the curing kinetics of two-component epoxy coatings. Various kinetic parameters (activation energy E, pre-exponential factor A, order of reaction n and rate constant k) have been determined. The kinetic parameters help us to understand the reaction at a molecular level. The differential scanning calorimeter (DSC) was used to determine these parameters. The study has been used to investigate the effect of the amine molecular structure on the reactivity with epoxy resin. The epoxy resin used was diglycidyl ether of bisphenol A (DGEBA) having an EEW of 187 g/equ. Four different curing agents; an aliphatic, cycloaliphatic and aromatic polyamine along with a polyamide (based on dimer fatty acid and polyamine) have been selected for the study. Using kinetic modeling, the reaction mechanism was determined and found to be dependent on molecular mobility, steric hindrance and phase heterogeneity of reactants and cured network. The reaction mechanism changes from autocatalytic for the DGEBA-polyamine system to non-catalytic for the DGEBA-polyamide system. The kinetic model helps us to predict the extent of reaction as a function of time at any temperature. The techniques presented in this paper can be used to design better corrosion resistant coating systems. |
| Note de contenu : |
- Dynamic experiments
- Isothermal experiments
- Relative reactivity of the hardeners (from isothermal experiments)
- Reaction mechanism (from isothermal experiments)
- Kinetic modeling (to verify autocatalytic and non-catalytic reaction mechanism)
- Kinetic parameters : order of reaction (n et m) and rate constant k
- Activation energy (E) and frequency factor (A)
- Prediction of gel time at any temperature (through kinetic modeling)
- Calculation of optimum curing agent concentration by DSC |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=11478 |
in PAINTINDIA > Vol. LVII, N° 6 (06/2007) . - p. 69-92
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Assessment of relative reactivities and kinetics of various polyamine and polyamide hardeners with epoxy resins for designing high performance epoxy coatings using differential scanning calorimetry in PAINTINDIA, Vol. LVII, N° 6 (06/2007)
