SynopsisAbout 40 epoxide-mine network polymers with glass transition temperatures ranging from 0 to 232°C were investigated, about one-third being reported for the first time. The glaw transition temperature T ' , of the corresponding linear copolymers was first calculated by use of an additivity law whose physical validity was carefully checked. Then the contribution of crosslink mers was determined, and various physical and empirical approaches of the effect of crosslinking on TR were compared. The results gave evidence in favor of the DiMardo approach. A predictive relationship based on these considerations is proposed.DGEBA-DDM epoxide-amine series5 (see below for the designating code). It has been shown however that eq. (1) cannot be applied to systems of high crosslink density such as polye~ters,~ a t least because the "copolymer effect" of the crosslinking species cannot be neglected. In this case free volume7 or more general considerations5 would lead to where x , is a parameter characterizing the network composition (segments,
SynopsisThe photo and thermal oxidation of various epoxide-amine tridimensional polycondensates is studied by IR spectrophotometry and DSC. The network degradation results in a decrease of the glass transition temperature (TJ, which is correlated with the quantity of amide groups formed. For each system, the relative yield in skeleton breaks increases with the intensity of internal stresses. A mechanism involving the fl scission of a amino alkoxy macroradicals resulting from oxidation of constrained segments of the network is proposed.
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