E. S. Tsobkallo

Effect of the Level of Preliminary Deformation on the Stiffness of Synthetic Fibres

The deformation stiffness of synthetic fibres increases significantly (by 3 and more times) as a result of preliminary stretching. The stress—strain diagram of the initial synthetic fibre can be used to predict the character of the change in the deformation stiffness in different stages of preliminary elongation. In the stretching segments where destructive processes are weakly manifested, the stiffness of the stretched fibres increases with an increase in the deformation. In the region of intensive molecular destruction processes, the deformation stiffness of the stretched fibres almost does not change, which is due to overlap of competing processes: structure ordering and molecular chain breaking.

Mechanical and Conducting Properties of Polypropylene Fibers Filled with Carbon Nanotubes with Functionalized Surface

A procedure for functionalization of the surface of multiwall carbon nanotubes, based on treatment of the nanofiller with a strong oxidant and 1-hexadecylamine and aimed to improve the compatibility of nanotubes with a polypropylene matrix, was examined. Variation of the mechanical and electrical properties of the composite fiber based on polypropylene in relation to the concentration of the modified nanotubes was studied.

Recovery Properties of Amide Fibres Fabricated from Polymers with Different Molecular Chain Rigidity at High Temperatures

Increasing the temperature significantly alters the character of accumulation of residual deformation in Armos fibre fabricated from a rigid-chain polymer due to elimination of moisture and breaking of hydrogen bonds of the “polymer—water—polymer” type. Accumulation of residual deformation in Terlon fibres at high temperatures takes place differently than in Armos. This is due to the difference in the degree of crystallinity of these fibres fabricated from rigid-chain polymers. No significant changes in the character of accumulation of residual deformation with an increase in the temperature were observed in Fenilon fibre fabricated from a polymer with medium chain rigidity and capron fibre fabricated from a flexible-chain polymer.

Structural Aspects of the Thermodynamics and Mechanics of Interaction Between Aramid Fibers and Water

We have used sorption and physicomechanical methods to study the effect of water in the vapor and liquid phases on the supermolecular structure of partially crystalline and liquid-crystalline polymer systems.

Study of Strength and Relaxation Properties of Polyester Surgical Suture Threads

We have studied the details of the mechanical behavior of polyester (Lavsan) twisted and braided surgical suture threads, including threads coated with the fluorinated rubber SKF-26. We show that application of this coating to the surface of twisted or braided suture threads makes it possible, without reducing the biocompatibility, strength or handling properties, to eliminate wicking, make them atraumatic, and improve surgical knot security. We have found that creep in twisted suture threads is twice as great as in braided threads. We have established the nonlinearity of the viscoelastic behavior of polyester surgical suture threads over the entire working range for loading on the suture material.

Influence of the Concentration and Shape of Carbon Fillers on the Mechanical Properties of Polypropylene Fibers

Polypropylene fibers containing various concentrations of spherical (technical carbon) and anisotropic (nanofibers, nanotubes) carbon nanoparticles were prepared under laboratory conditions. The mechanical properties of the composite fibers were determined. It was shown that their strength and elasticity modulus increased by ~1.5 times only upon adding small concentrations (1-5 mass%) of anisotropic particles. Adding technical carbon at all concentrations decreased the fiber strength and fracture bending with an insignificant increase of elasticity modulus.

Estimate of the Main Energy States of Synthetic Modified Polyolefin Shape−Memory Yarn

We consider the heat shrink process for heat-shrinkable modified polyolefin shape-memory yarn held at different temperatures for different times. We give a general equation for deformation of a shapememory polyolefin yarn. Based on experimental data and the general deformation equation, we have estimated the main energy states of a shape-memory polyolefin yarn.

Strength and relaxation properties of synthetic shoe thread

A comparison of the strength and deformation properties of Lavsan and Lavsan—Siblon shoe thread showed that when Siblon fibres are added, the strength of the fibres changes extremely little, but their elasticity improves; this is responsible for the advantages of the modified fibre, during use. The existence of three segments on the stress—strain diagrams of the fibres related to different mechanisms of deformation was demonstrated. The first and second segments in the diagrams, corresponding to the region of practical use, are larger for Lavsan—Siblon fibre than for lavsan fibre. A correlation was established between the type of stress—strain diagram and the character of accumulation of residual strains in the fibres, which allows replacing the laborious measurements of residual strains by obtaining the stress-strain diagrams. Relaxation of stresses in the fibres was quantitatively described and predicted. It was shown that the proposed descriptive method can be used without additional improvements in the first deformation segment, in the region of low residual strains.

Effect of preliminary loading on the deformation and strength properties of high-strength fibres

High-strength, high-modulus polyethylene fibres fabricated with gel technology is similar to low-modulus fibres of the olefin and amide series (Capron, polypropylene) with respect to the character of the correlation of the stress—strain diagrams and curve of accumulation of the residual component of deformation. The residual deformation component is relatively large both for high-strength PE fibre and for p-polyamide fibres. The differences in the character of accumulation of the plastic component in these fibres are due to the fact that the residual strains arising in high-strength PE fibre, as in other flexible-chain polymer fibres (polypropylene, Capron) is initiated by breaking of bonds in the main chain. In p-polyamide fibres (Armos, SVM, Terlon, Kevlar), plastic strains arise due to highly elastic deformation “frozen≓ by hydrogen bonds and orientation of molecular chains. Preliminary deformation affects the strength properties of high-modulus fibres differently: in PE fibres, the strength decreases, it increases for Armos and SVM fibres, and remains unchanged for Terlon fibre. This difference is to a great degree due to the difference in the types of intermolecular interaction in fibres of the olefin and amide series. For all fibres investigated, the character of accumulation of the residual deformation component can be correlated with the type of stress—strain diagram, which will allow creating simpler methods of evaluating residual strains.