ABSTRACT
The term “structural stabilization” in reference to polymers in general and to their melts specifically is known enough a time long ago [1]. However, earlier it was supposed, that the structural stabilization applicable only to solid state of polymers, where the structure (specially for semicrystalline polymers) is pronounced, whereas polymeric melt was considered as structureless state. Besides, the absence up to the last time of quantitative structural models of polymers in any of the mentioned states forced to restort to indirect methods of the structure estimation. So, the authors [1] believe, that the structural stabilization idea consists in such structural-physical material modification, which supresses a molecular mobility in polymer, specially small-scale high-frequency motionts responsible for chemical reactions. The molecular mobility reduction decreases chemical reactivity and rises the material stability [1]. The attempt of consideration of topological disorder influence (the degree of polymer chains entanglement) on thermooxidative degradation processes in papers [2, 3] was undertaken. It is quite easy to see, that in both cases indirect characteristics of structure were used.Structure notion is key in mathematics, physics, chemistry, biology and other sciences [4]. General conception of structure is satisfied by the Kre-ber definition: “Each system consists of elements, ordered by a definite way and connected by definite relations. Under system structure we understand the mode of elements organization and character of connection between them” [5].It is obvious, that in polymer’s case the structural element of the smallest order is a statistical segment, which expresses in essence the individuality of any polymer [6, 7]. In polymer’s physics structure is defined, as micro-and macrostructure of polymer and also as the connection structure-composition-property [4].The rapid development of fractal analysis methods in the last 20 years allowed to change the shaped situation. It is experimentally shown [8, 9], that the solid polymers are fractal objects in interval of linear scales ~ 3-50 A. Besides, as Vilgis showed [10, 11], the macromolecular coil in melt is the fractal having dimension A/«2.5. These results involve two very important consequences. Firstly, direct, but not indirect, characteristic of polymer’s structure appears in both mentioned states, since fractal (Haus-dorff) dimension characterizes the elements distribution of macromolecular coil in space, i.e., truly structural parameter [12]. Secondly, the correct
description of fractal objects is possible only within the framework of fractal analysis and any application of Euclidean geometry is more or less precise approximation [13]. Proceeding from this, in the base of assumed structural treatment of thermooxidative degradation processes is appointed the postulate of fractal nature of polymer’s structure.At the beginning of the monograph we will briefly consider the physical bases of applied structural models and their main parameters determination methods. Further the structural aspects of gas transport processes, physical aging and thermooxidative degradation in polymers will be described. As the main structural models the fractal analysis and connected with it cluster model of polymer’s amorphous state structure and irreversible aggregation models are used. Such treatment allows to demonstrate that the polymer’s structure is often more important factor at thermooxidative degradation than their chemical constitution. The other important moment, which allows to consider mentioned approaches, is the role of structure in polymer melts oxidation. As mentioned above, earlier this role is underestimated.The base for understanding of structural stabilization gives anomalous diffusion of oxidant molecules on fractal structure of both solid polymers and polymeric melts. The important part of this problem is structure connectivity characterized by its spectral dimension. In virtue of this branched (cross-linked) polymers have smaller diffusivity in comparison with linear.The physical aging of polymers reflects their thermodynamically nonequilibrium (fractal) structure. Such approach allows to obtain the quantitative estimation of structure (and, consequently, properties) change of polymers as a function of aging duration.For characterization of polymeric melt structure the macromolecular coil fractal dimension is used. Such approach allows to quantitative estimation and prediction of kinetic curves of oxygen consumption and thermooxidative degradation limiting degree. Besides, we obtain the analytical structural criterion of transition of kinetic curves type from autodecelerated up to autoaccelerated. The fractional derivation using allows to introduce principally new postulate: is subjected to oxidation only a part of polymeric coil determined by its structure. REFERENCES 1. Emanuel N.M., and Buchachenko A.L., Chemical Physics o f Molecular Failure and Polymer’s Stabilization, 1988, Moscow, Nauka, 368 p. (Rus)2. Monakhova T.V., Bogaevskaya T.A., and Shlyapnikov Yu.S., Vysokomol. Soedin., 1995, vol. 37B(1), pp. 160-162. (Rus)3. Shlyapnikov Yu.S., and Kolesnikova N.N. In book: Aging o f Polymers, Polymer Blends and Polymer Composites. Ed. Zaikov G., Buchachenko A.L.,
