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The Curing Influence on Molecular and Structural Characteristics of Epoxy Polymers

2 The Curing Influence on Molecular and Structural Characteristics of Epoxy Polymers [Pg.209]

At present it is well known [26-28] that a change in the crosslinking density for crosslinked polymers results in a number of important variations in characteristics glass transition temperature T, mechanical properties and so on. In turn, for linear polymers correlations between molecular characteristics exist, for example, between macromolecule cross-sectional area 5, chain rigidity a and their macroscopic properties [2, 24, 29, 30]. It can be expected that chemical crosslinking exercises influence the molecular characteristics of crosslinked polymers thereby influencing their structure and properties. [Pg.209]

To test the accuracy of this supposition the authors [31] used the integral molecular parameter (S/CJ. By its physical essence it is similar to parameter a/a (where a is chain thickness), used earlier in papers [29, 30]. However, the parameter is not as vague as G [24]. This is due to determination of the parameters c and C, the first of which depends on the angle of the macromolecule valence bonds and the second on the length of these bonds. The bond lengths are usually determined considerably more precisely than the valence angles. It is probable therefore that in recent years has been widely applied as a molecular characteristic [32, 33]. [Pg.209]

For independent estimation of the value of S the methods stated above [2], based on the application of wide angle X-ray diffractometry, can be used. Within the frameworks of this method an interconnection between Bragg s interval d, calculated [Pg.209]

Independent checking of the accuracy of quantitative estimations of values of 5 and can be carried out as follows. Within the frameworks of the plasticity fractal concept [38, 39] and the cluster model of the amorphous state structure of polymers [5, 6] it has been shown that the yield process is realised in densely packed regions of the structure (clusters). In addition, the relative fraction of the clusters is equal to the yield process realisation probability (1 -%) [39]. The probability (1 x) calculation method is given in paper [39] and the value p can be determined according to Equation 1.11. If the values of S and were calculated correctly, then the identity should be carried out [39]  [Pg.211]




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