Fracture Zhurkov kinetic theory

The major thrust of the stress MS studies to date has focused on gathering evidence to support the kinetic theory of fracture proposed by Zhurkov. For the Zhurkov kinetic theory of fracture to be applicable to the material in question, not only must the mechanical and thermal degradation products be identical, but both processes must follow the same degradation mechanism. 

Only if the answers to all these questions are aflBrmative can we use the Zhurkov kinetic theory of fracture to explain the degradation processes. The evidence gathered to date which is germane to this subject is summarized below. 

Following the earlier works of Eyring, Zhurkov, and Bueche, these and other authors have continued to develop different aspects of the kinetic theory of fracture. Particularly in the USSR fracture data have been interpreted in terms of the failure of regular, nonmorphological model lattices (e.g., 54—58). Gubanov et al. 

There has been a prevailing theory that oxidative degradation is accelerated by mechanical stress [100]. This theory is based on fracture kinetic work by Tobolsky and Eyring [101], Bueche [102, 103, 104], and Zhurkov and coworkers [105, 106, 107]. Their work resulted in an Arrhenius-type expression [108] sometimes referred to as the Zhurkov equation. This expression caused Zhurkov to claim that the first stage in the microprocess of polymer fracture is the deformation of interatomic bonds reducing the energy needed for atomic bond scission to U=U0-yo, where U0 is the activation energy for scission of an interatomic bond, y is a structure sensitive parameter and o is the stress. 

One further topic merits discussion in this section in view of its success in dealing with the mechanical properties of oriented fibres, which are after all anisotropic polymers. That is the theory of kinetic fracture, developed mainly by Zhurkov and co-workers. Evidence has been presented from electron spin resonance (e.s.r.X " mass spectrometry, and infra-red spectroscopy that when highly oriented fibres or heavily cross-linked rubbers experience a tensile stress (along the axis for fibres) an appreciable fraction of main-chain bonds are broken by the applied stress. These scission events are observed to occur more or less homogeneously throughout the fibre and are not localised in the fracture plane. Many sets of data show that the lifetime tb of a fibre under stress is described approximately by the following equation... 

In the fracture theory of Hsiao-Kausch [60, 61] the state of orientation of a polymeric solid is explicitly recognized. The theory combines the kinetic concept of Zhurkov or Bueche and the theory of deformation of anisotropic solids developed by Hsiao [59]... 

On the other hand, fracture mechanics theory suggests the rupture may be due to weak intercrystalline affinity [18-21], agglomeration of amorphous regions [22-24], or some combination thereof [9,18], However, these broad mechanisms are unlikely to be mutually exclusive, and they lead to similar mathematical representations differing only in the rate-controlling step of many kinetic phenomena [6,10], Because the Zhurkov theory is more widely-accepted and has a well-developed basis in physics, it will be highlighted here. 

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