G. Ya. Slutsker

Creep and fracture kinetics of polymers

The creep kinetics and the fracture kinetics of oriented linear polymer (polypropylene) are compared. The distributions (scatter) of the specimen lives and the steady-state creep rate are studied on series of identical specimens loaded under the same conditions (load, temperature). It is found that the scatter of the specimen lives is significantly larger than the scatter of the creep rates at the same activation energy of fracture (the measure of which is the life) and creep. This finding reflects a localized character of fracture (break) of specimens and a delocalized character (involvement of the entire specimen volume) of creep. It is concluded that the equality of the activation energies of both processes is caused by the elementary acts of fracture of an oriented polymer (breaking of chain molecules), and they open up possibilities for creep acts, i.e., conformation transitions, in a polymer.

Broadening of Relaxation and Retardation Spectra Due to Uniaxial Orientational Drawing of Polyamide Films

The initial and quasi-equilibrium values of relaxation modulus, the mean statistic retardation and relaxation times, and the parameters of retardation and relaxation time distributions have been estimated from the corresponding creep, elastic relaxation, and stress relaxation curves. Changes in the above characteristics with an increase in the draw ratio are analyzed.

Initial stage of stress relaxation in oriented polymers

The initial stage of stress relaxation, i.e., a decrease of the stress with time in an extended solid at a fixed length of the specimen, has been studied in oriented fibers of a linear polymer, polypropylene, chosen as the object of investigation. Experimental data have been obtained, and the stress in the object from the beginning of tensile loading of the specimen has been analyzed. It has been found that the stress relaxation caused by thermal fluctuation conformational transitions in stretched chain polymer molecules occurs from the beginning of the stretching of the polymer fiber. The time dependence of the stress relaxation of polypropylene fibers in all initial stages of deformation of the fibers has been elucidated.

Elastic properties of polypropylene and polyvinylidene fluoride monofilaments and meshed endoprosthses based on them

Investigations were carried out to determine the interrelation between elastic properties of polypropylene and polyvinylidene fluoride monofilaments and meshed implants (endoprostheses) based on them that are used in reconstructive-restorative surgery. The structure of the warp-knitted endoprostheses is approximated by a mesh having rectangular cells possessing anisotropic elasticity in orthogonal directions. In this regard, for a comparison of elastic properties of filaments and filaments as constituents of meshed fabrics, a switch from the coefficient of elasticity of the mesh to Young’s modulus of the filament as a constituent of the prostheses was made. It is shown that the coefficients of elasticity of the prostheses are proportional to the elasticity coefficients of polymer filaments usable for their fabrication.

Quantitative correlation of creep and stress relaxation in synthetic fibres

The quantitative correlation of creep and stress relaxation was determined. The reliability of the indicial equation and calculated deformation characteristics for describing the different conditions with a given law of deformation was confirmed.

Viscoelastic properties of technical fabrics

ConclusionsThe possibility of making a quantitative description of the viscoelastic properties of fabric constructions has been demonstrated.It has been found that the form of weave only slightly affects the viscoelastic properties of the investigated specimens.It has been shown that a quantitative description of the deformation properties of specimens of various structures can be carried out using averaged parameters.

Deformation of technical purpose woven tapes

ConclusionsAn analogy has been found between the viscoelastic properties of yarns and fabrics which makes it possible to apply a previously developed rapid method of determining deformation characteristics to fabrics.The possibility of applying the nonlinear hereditary viscoelasticity equation for calculating the stretching diagrams of woven tapes, with allowance for the specifics of their deformation, has been established.