Polymer Bulletin

, Volume 71, Issue 5, pp 1241–1262 | Cite as

Influence of rubber on the curing kinetics of DGEBA epoxy and the effect on the morphology and hardness of the composites

  • Angel Romo-Uribe
  • Jose Antonio Arcos-Casarrubias
  • Araceli Flores
  • Cintya Valerio-Cárdenas
  • Agustin E. González
Original Paper

Abstract

The influence of the end groups of two liquid rubbers on curing kinetics, morphology, and hardness behavior of diglycidyl ether of bisphenol-A based epoxy resin (DGEBA) has been studied. The rubbers are silyl-dihydroxy terminated (PDMS-co-DPS-OH) and silyl-diglycidyl ether terminated (PDMS-DGE). Crosslinking reactions, investigated by shear rheometry, ranged 90–110 °C, using a constant concentration (5 phr) of liquid rubbers and 1,2-Diamino cyclohexane (1,2-DCH) as hardener agent. The gel time, tgel, of the neat epoxy significantly decreased when adding the elastomers, more so for the silyl-dihydroxy terminated elastomer; at 110 °C the reaction was nearly complete before rheological test started. The results suggest that the elastomers induced a catalytic effect on the curing reaction. Scanning electron microscopy revealed phase separation of the elastomer during the curing reaction with rubber domains about 5 μm size. However, the DGEBA/dihydroxy terminated elastomer composite cured at 110 °C exhibited a homogenous morphology, that is, the rapid reaction time would not allow for phase separation. Water contact angle tests evidenced either more hydrophilic (silyl-diglycidyl ether terminated rubber) or more hydrophobic (silyl-dihydroxy terminated rubber) behavior than the neat epoxy. The latter effect is attributed to the presence of aromatic rings in the backbone structure of PDMS-co-DPS-OH. Microindentation measurements show that the elastomers significantly reduced the hardness of the epoxy resin, the DGEBA/ether terminated composite exhibiting the lowest hardness values. Moreover, hardness increased as reaction temperature did, correlating with a reduction of microdomains size thus enabling the tuning of mechanical properties with reaction temperature.

Keywords

Epoxy DGEBA Rubber Shear rheometry Curing reaction 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Angel Romo-Uribe
    • 1
  • Jose Antonio Arcos-Casarrubias
    • 2
  • Araceli Flores
    • 3
  • Cintya Valerio-Cárdenas
    • 1
  • Agustin E. González
    • 1
  1. 1.Laboratorio de Nanopolimeros y Coloides, Instituto de Ciencias FisicasUniversidad Nacional Autonoma de MexicoCuernavacaMexico
  2. 2.Division de Ingenieria Quimica y BioquimicaTecnológico de Estudios Superiores de EcatepecEcatepecMexico
  3. 3.Instituto de Estructura de la MateriaIEM-CSICMadridSpain

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