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Chemorheology of crosslinked epoxy resins subjected to large strains
Author(s) -
Buchman A.,
Katz D.
Publication year - 1979
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760191308
Subject(s) - materials science , epoxy , composite material , birefringence , layer (electronics) , inert gas , polymer , ageing , core (optical fiber) , oxygen , strain (injury) , orientation (vector space) , optics , organic chemistry , chemistry , medicine , physics , biology , genetics , geometry , mathematics
The previously reported work on chemorheological changes occurring in two epoxy resins when aged under large strains at temperatures above their T g was extended. Ageing times up to 100 h were applied and the phenomenon of orientation occurring in these samples was investigated, mainly by measurements of their birefringence index. It was found that the orientation of the air‐aged samples, when studied at room temperature, depended on the ageing conditions (strain, temperature, time) and was not uniform throughout the bulk of the samples, being higher in two narrow external layers and lower in the core layer. After reheating oriented samples in air without strains for different lengths of time at temperatures above T g , disappearance of the orientation in the external layers was observed. This is probably due to oxidation and degradation occurring in the network and scission of part of the network links, mainly those strained due to orientation. The decrease of orientation, especially in the inner layers of the polymer samples, was much slower when the reheating of the oriented‐ and unstrained samples took place in an inert atmosphere, this showing again the great influence of oxygen when it participates in ageing and heating processes of epoxy resins.