Epoxy polymers sulfur-containing

Polymer mechanical properties are one from the most important ones, since even for polymers of different special-purpose function a definite level of these properties always requires [20]. Besides, in Ref [48] it has been shown, that in epoxy polymers curing process formation of chemical network with its nodes different density results to final polymer molecular characteristics change, namely, characteristic ratio C, which is a polymer chain statistical flexibility indicator [23]. If such effect actually exists, then it should be reflected in the value of cross-linked epoxy polymers deformation-strength characteristics. Therefore, the authors of Ref [49] offered limiting properties (properties at fracture) prediction techniques, based on a methods of fractal analysis and cluster model of polymers amorphous state structure in reference to series of sulfur-containing epoxy polymers [50]. 

It is curious to note, that sulfur-containing epoxy polymers the greatest deformability is reached at the greatest chemical cross-linking density realized at = 1.20 [49] (see Fig. 7.9). This nontrivial observation can be explained within the frameworks of the fractal analysis. As it is known [17],... 

The Eq. (7.13) was used for the studied epoxy polymers strength (fracture stress) Oj. calculation. In Fig. 7.11 the comparison of strength values Op obtained experimentally and calculated according to the Eq. (7.13), for sulfur-containing epoxy polymers is adduced. As the adduced comparison shows, the good conformity of theory and experiment is obtained. 

FIGURE 7.10 The dependence of fractal dimension of chain part between clusters on if j value for sulfur-containing epoxy polymers [49]. 

Formation of floccules is interpreted theoretically within the frameworks of the gelation period concept [137] (the indicated concept is stated in more detail in Chapter 3). The authors of paper [138] explained the formation of floccules within the frameworks of synergetics and fractal analysis in the example of sulfur-containing epoxy polymers (SCE) cured by aromatic diamines (4,4 -diaminodiphenylsulfone (SCE-DADPS) and 4,4 -diaminodiphenylmethane (SCE-DADPM)) and iso-methyltetrahydrophthalic anhydride (SCE-IMTHPhA) [139]. 

Mechanical properties of polymers are among the most important, since a certain level of these properties is always required even for polymers of different special-purpose functions [50]. In papers [38, 51] it has been shown that the curing process of the chemical network of epoxy polymers with the formation of nodes of various density results in a change in the molecular characteristics, particularly the characteristic ratio C. If such an effect actually exists, then it should be reflected in the deformation-strength characteristics of crosslinked epoxy polymers. Therefore the authors [49] offered methods of prediction of the limiting properties (properties at fracture), based on the notions of fractal analysis and the cluster model of the amorphous state structure of polymers, with reference to a series of sulfur-containing epoxy polymers [52, 53] (see also Section 5.4). 

The sulfur-containing epoxy polymers, cured by both aromatic diamines (DADPS and DADPM) and Iso-methyltetrahydrophthalic anhydride (IMTHPhA) (see Section 5.4), were studied. The fact that two of the studied epoxy polymers showed plastic fracture in impact loading conditions (SCE-DADPS - 1.2 and SCE-DADPS - 1.3, where the figure in conditional sign indicates the value of KJ. The diagram load-time (P -1),... 

Poly sulfide compounds that are compatible with epoxy resins are liquid elastomers at room temperature. The most significant commercial resin of this type is LP-3 from Toray. The predominant product is a mercaptan-terminated liquid polymer (LP) that contains approximately 37% bound sulfur (see Fig. 7.2). It is the high concentration of sulfur linkages that provides these products with their unique chemical properties. A sulfur odor is noticeable during processing, making ventilation important. 

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