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A dynamic mechanical study of the effect of chemical variations on the internal mobility of linear epoxy resins (polyhydroxyethers)
Author(s) -
Van Hoorn H.
Publication year - 1968
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1968.070120422
Subject(s) - glass transition , epoxy , torsion pendulum clock , polymer , polymer chemistry , steric effects , diglycidyl ether , natural rubber , activation energy , bisphenol , materials science , polar , chemistry , ether , bisphenol a , thermodynamics , composite material , organic chemistry , physics , quantum mechanics , astronomy
A series of polyhydroxyethers prepared from various bisphenols and their diglycidyl ethers has been investigated for dynamic mechanical behavior in a temperature range from −180°C. up to their glass‐rubber transition region, employing a torsion pendulum method for frequencies of about 0.1 hz and a vibrating‐reed method for frequencies of about 100 hz. Glass‐rubber transition temperatures ranged from 85 to 170°C. and are interpreted in terms of polarity, segment bulkiness, and packing capability of the polymer molecules. In most cases the activation energy of this transition was found to be extremely high, of the order of 500 kcal./mole. Fair consistency is found regarding the role played by methyl or chlorine substitution of the bisphenol rings, increasing bulkiness and steric hindrance, but reducing polar interaction. At least one and, in some cases, two secondary transitions were found well below the glass‐rubber transition region. One is ascribed to a change in mobility of the glyceryl ether segments common to all nonesterified polymers of the series. While this is in general agreement with the findings of other authors, we found a spread in transition temperature values (−70 to −102°C. at ≈ 1 hz) and activation energies which can be related to the detailed chemical structure of these polymers. With methyl substitution of the bisphenol rings of the highly polar polymers symmetry seems to be an important factor. In addition, another secondary transition appeared, which we ascribe to an onset of ring rotation.