Calculation of the glass transition temperature of network polymers and determination of the chain fragment between crosslinks

Peculiarities of the structure and properties of highly cross-linked polymer networks

“…To formulate this concept, Eqn (6) was `calibrated' using experimental glass transition temperatures of numerous well-characterised cross-linked systems. 5 It turned out that the best agreement between the calculated and experimental results is achieved with the definition of the cross-link point given in the Introduction.…”

“…Figure 3. Dependences of the density on the molecular weight of the repeating fragment obtained by the hydrostatic weighing method (1,4), calculations (2,4), and according to thermal dilatometric data (3,5) for cured epoxy resins containing azelaic acid (1 ± 3) and oleic acid (4,5). ylic azelaic acid (or monocarboxylic oleic acid) added to the compositions to lengthen the linear fragments or to introduce `dangled' chains are shown in Fig.…”

“…3,7,8 For the most part, actual networks correspond to an intermediate case since they contain rather long but finite-length linear fragments between cross-link points. Generalisation of Eqns ( 5) and (5a) taking into account the effects of both linear fragments and cross-link points of the network on the glass transition temperature resulted in the following relationship: 5,6…”

“…This equation can be applied both to extremely sparse and to most highly cross-linked networks as well as to the networks of intermediate structure. In fact, if the network consists virtually of nothing but linear fragments, the effect of cross-link points can be neglected and Eqn (6) becomes Eqn (5). On the contrary, if the network consists of nothing but cross-link points, then Eqn (6) becomes Eqn (5a).…”

“…E-mail: andrey@ineos.ac.ru atom, and their nearest substituents. 5,6 A decrease in the number of repeating units between cross-link points (if it amounts to several tens) affects insignificantly the glass transition temperature, the molar volume, the refractive index, and some other characteristics. However, when the number of the repeating units between cross-link points is very small (several units), its decrease results in abrupt changes in the properties (Fig.…”