Dependence of maximum recoverable deformation of linear flexible‐chain polymers on limiting extension of the chains

Dreval, V. E.; Vinogradov, G. V.; Radushkevich, B. V.

doi:10.1002/pol.1984.180220701

Cited by 8 publications

(3 citation statements)

References 9 publications

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“…These values considerably exceed recoverable fracture strains for crosslinked rubbers. The analysis of the results for 1,2-polybutadiene and a number of other polymers leads to an important conclusion that the maximum of the e* (8) curve corresponds to the limiting degree of straightening of the macromolecules [5,18,19]. The pertinent data are presented in figure 9.…”

Section: The Relaxation Transitions In Linear Polymers In Uniaxial Exmentioning

confidence: 97%

Uniaxial extension and shear in combination with cyclic straining as a promising method for studying the viscoelasticity of polymers over a wide range of stresses and strains atT > T g

1985

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Simple relations are found between the fracture strains, the long-term durability and the initial values of parameters characterizing polymer rheology at deformation rates and stresses approaching zero. Fracture regimes are determined by two groups of parameters. One includes critical values of stresses. They are invariant with repect to temperature and molecular weight of the polymers; the values of critical stresses for different polymer compositions differ by a factor of 10 to 20. The second group of critical parameters includes the rates of deformation determined by the initial viscosity. The latter may vary by many orders of magnitude. There exists a universal critical value determining polymer fracture independent of linear macromolecule composition, its molecular weight, the temperature and the way of attaining a given state. This value is the recoverable strain and is equal to 0.5 according to Hencky. There exists a relation between the maximum value of recoverable strain in the transition region from the rubbery to the leathery state and the extensibility of macromolecules for polymers with various molecular weights. Quenching of the polymer near the maximum recoverable strain makes it possible to obtain high strength samples. Overspurt regimes for polymer flow have also been studied. It has been shown that this causes polymer static electrification. Simple and unique dependences of the charge density on temperature and polymer molecular weight have been established.

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Section: The Relaxation Transitions In Linear Polymers In Uniaxial Exmentioning

confidence: 97%

Uniaxial extension and shear in combination with cyclic straining as a promising method for studying the viscoelasticity of polymers over a wide range of stresses and strains atT > T g

1985

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“…173 There is a special point in Fig. However, a more general idea was advanced: 175 it was proposed that the maximum elastic deformation (the maximum on the curve in Fig. It was suggested 174 that the maximum value of the elastic deformation in extension of polymer melt is close to 2 (it corresponds to the draw ratio about 7.3).…”

Section: Liquidsmentioning

confidence: 99%

Liquids

Malkin

Isayev

2012

Rheology Concepts, Methods, and Applications

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“…Application of a force or thermal process on PAN fibers can lead to large plastic deformations, accompanied by drastic structural changes in both amorphous and crystalline phases. [1][2][3][4] Residual stress that is generated during the spinning process of PAN fibers released at the beginning of the thermal stabilization process prior to a chemical reaction and causes structural deformation in PAN macromolecules. 5 As a result, thermal-induced stress is developed due to tendency of chains in the disordered phase to undergo entropic relaxation.…”

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A Novel Method for Investigation of Entropic Stress in Prestabilization of PAN‐Based Precursor Fibers

2015

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ABSTRACT:Applying stress in the fiber axis direction during the prestabilization process is the best method to control entropic relaxation. Evaluation of entropic stress is necessary for exact determination of required imposed stress. Accordingly, in this paper three types of special-grade polyacrylonitrile (PAN) fibers with different physical-mechanical properties and morphological characteristic are studied. To determine thermal-induced entropic stresses, we use the thermomechanical analysis method from room temperature to beginning of chemical reactions under certain stresses. It is shown that three thermophysical behaviors including the first return, second return, and sans return occurs under certain stresses during the thermal process. There are distinct temperatures for the first and second return behaviors, in which fibers return to primary length after shrinkage or elongation. These temperatures depend on imposed stress during prestabilization. We found that if no elongation or fiber shrinkage occurs in a specific stress and temperature, it shows that imposed stress is equivalent to thermal entropic stress. Changes in shrinkage as a function of temperature for various external imposed stresses are also observed. According to our findings, the onset of entropic stress strongly depends on the orientation index of the paracrystalline region. The maximum entropic stress occurs in the rubbery flow region in amorphous phases and can be obtained from a derivative of the second-order polynomial trend line of the entropic stress-temperature diagram.

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Dependence of maximum recoverable deformation of linear flexible‐chain polymers on limiting extension of the chains

Cited by 8 publications

References 9 publications

Uniaxial extension and shear in combination with cyclic straining as a promising method for studying the viscoelasticity of polymers over a wide range of stresses and strains atT > T g

Uniaxial extension and shear in combination with cyclic straining as a promising method for studying the viscoelasticity of polymers over a wide range of stresses and strains atT > T g

Liquids

A Novel Method for Investigation of Entropic Stress in Prestabilization of PAN‐Based Precursor Fibers

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