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Network structure and plasticization of epoxy‐based resins
Author(s) -
Apicella A.,
Nicolais L.
Publication year - 1987
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19870070111
Subject(s) - sorption , diglycidyl ether , differential scanning calorimetry , epoxy , materials science , bisphenol a , plasticizer , adsorption , volume (thermodynamics) , chemical engineering , hydrogen bond , composite material , polymer chemistry , thermosetting polymer , moisture , miscibility , molecule , thermodynamics , polymer , chemistry , organic chemistry , physics , engineering
The sorption behaviour of water molecules in epoxy‐based thermosetting networks is discussed and related to the modifications of their properties. The hypothesized sorption modes and the corresponding mechanisms of plasticization are discussed on the basis of experimental vapor and liquid sorption tests, differential scanning calorimetry (DSC), thermomechanical analysis (TMA) studies, and dynamic mechanical analyses. Three modes of moisture sorption are assumed: increase in the free volume of the system, hydrogen bonding onto hydrophilic groups present in the network and adsorption onto the surfaces of “holes” which define the excess free volume of the glassy structure. The less stiff Diglycidyl ether of bisphenol‐A (DGEBA) systems have no appreciable sorption via hydrogen bonding, but rather most of the moisture absorbed is due to the free volume increase and adsorption in the “holes”. On the other hand, the stiffer Tetraglycidyl Diaminodiphenyl Methane (TGDDM) systems absorb more moisture through significant hydrogen bonding rather than by the free volume increase. High plasticizations, evident as T g depressions by 30 to 80°C, are possible being experimentally observed for the stiffer TGDDM resins. Relationships derived from the free volume theory or the classical thermodynamic treatment may be used to describe the dependence of T g on the composition of miscible blends.