Polymers fracture process

Recent work by Dickinson on fracto-emission(36) indicates that ions, neutral particles, electrons and photons could be detected during the polymer fracture processes. The identification of these species during polymer wear may be of future research interests. 

The study of polymer fracture processes is based on the generalised relation time-temperature, given by S.N. Jurkov, which was expressed by G.N. Bartenev in the following form [843-846] ... 

It was also found [6], that in this case experimentally determined values of athermic fracture stress turn out to be essentially (2 3 times) smaller than theoretically calculated ones. A small values k 0.2 1.0) is one more important feature of nonoriented polymers fracture in impact tests. This means, that the stress on breaking bonds is essentially lower than nominal fracture stress of bulk sample. And at last, it was found out [7], that the value k reduces at testing temperature growth and the transition from brittle fiactuie to ductile (plastic) one. These effects explanation was proposed in Refs. [4-7], but development of fractal analysis ideas in respect to polymers lately and particularly, Alexander and Orbach woik [8] appearance, which introduced the fraction notion, allows to offer the major treatment of polymer fracture process [9, 10], including the dilaton concept [1-3] as a constituent part. 

Thus, the stated above results demonstrated, that fractal analysis application for polymers fracture process description allowed to give more general fracture concept, than a dilation one. Let us note, that the dilaton model equations are still applicable in this more general case, at any rate formally. The fractal concept of polymers fracture includes dilaton theory as an individual case for nonfractal (Euclidean) parts of chains between topological fixation points, characterized by the excited states delocalization. The offered concept allows to revise the main factors role in nonoriented polymers fracture process. Local anharmonicity ofintraand intermolecular bonds, local mechanical overloads on bonds and chains molecular mobility are such factors in the first place [9, 10]. 

Shogenov, V. M., Kozlov, G. V, Mikitaev, A. K. (1989). Prediction if Rigid-Chain Polymers Fracture Process Parameters. sokomolek. Soed. B, 31(11), 809-811. 

J.P. Berry, Fracture processes in polymeric materials. I. The surface energy of polyfmethyl methacrylate), J. Polymer Sci., 50, 107-115, 1961. 

A low-molecular-weight condensation product of hydroxyacetic acid with itself or compounds containing other hydroxy acid, carboxylic acid, or hydroxy-carboxylic acid moieties has been suggested as a fluid loss additive [164]. Production methods of the polymer have been described. The reaction products are ground to 0.1 to 1500 p particle size. The condensation product can be used as a fluid loss material in a hydraulic fracturing process in which the fracturing fluid comprises a hydrolyzable, aqueous gel. The hydroxyacetic acid condensation product hydrolyzes at formation conditions to provide hydroxyacetic acid, which breaks the aqueous gel autocatalytically and eventually provides the restored formation permeability without the need for the separate addition of a gel breaker [315-317,329]. 

During the initial fracturing process, a degradation, which results in a decrease of viscosity, is undesirable. The polymer in fracturing fluids will degrade at elevated temperatures. 

Since an understanding of the importance of any one process contributing to the failure in thermoplastics and the control over these processes is only partly attainable, a knowledge and understanding of the nature of endurance Hmits is of extreme importance for successful use of plastics, in particular engineered thermoplastics [27]. In terms of the failure type, polymer fracture may occur as a rapid extension of an initial defect, plastic flow of the matter and the thermally activated flow of the macromolecules. In all these cases, however, fracture is a localized phenomenon characterized by a large inhomogeneity of deformations. 

The analysis of the deformational behaviour of linear polymers allows us to understand the importance of plasticity in fracture behaviour of the glassy state. The same result is valid for the network glasses considered. Fracture processes in glassy polymers of epoxy-aromatic amines type were investigated in Refs. 87and64). The main results of the investigations can be summarized as follows ... 

The Role of Molecular Parameters in Contact Fracture Processes of Glassy Polymers... 

As the loading rate increases, thermal effects need to be accounted for and the analysis is extended to a coupled thermomechanical framework. Evidence of a temperature effect in glassy polymer fracture is found (e.g., in [2,3]) with a temperature increase beyond the glass transition temperature Tg. The influence of thermal effects on the fracture process is also reported. 

When the polymer is more ductile, several steps of stable and unstable crack propagation can successively occur during the fracture process of the sample. Figure 27.2 illustrates the observed fracture surface of such fracture behavior. 

Since Wf = U and A = It, Equation (14) is similar to Equation (12). It has therefore been argued [23] that the impact fracture energy at crack initiation in polymers with ductile behavior G is rather the essential fracture work we. Furthermore, the second parameter representing the variation of the impact fracture energy during stable crack growth, T, has been attributed to the work dissipated in the outer plastic zone and is not related to the fracture process [23]. 

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