Biophysical Properties of Foamed and Solid Polymers Used in Orthotics and Prosthetics

Orthotic and prosthetic materials should have good mechanical and antibacterial properties. Therefore, in our study, we consider four common foamed closed-cells and two solid polymeric materials regarding their mechanical behaviour and tendency for bacterial adhesion. For all materials, the surface roughness, hydrophobicity, zeta potential, tensile properties, hardness and CIE color parameters were measured. We found that foamed polymeric materials have higher roughness, higher hydrophobicity, lower Young’s modulus, lower maximum tensile strength and lower hardness than solid materials. Bacterial adhesion test measurements based on observation by scanning electron microscopy show much a lower adhesion extent of S. aureus on solid materials than on foamed materials. The measured biophysical properties could be the key data for users to select the optimal materials.

Determination of the melting point of solid polymers by rheological method

The rheological properties of polymer systems determine their deformation behavior and the relationship between stresses, strains and strain rates. We present the results of determining the melting points of solid polymer compounds by the rheological method. Tests were carried out using a rotary rheometer in an oscillating mode. Using the obtained thermomechanical dependences, the experimental data were compared with the values determined by standard analytical (capillary method) and thermal (differential scanning calorimetry) methods. The viscous and elastic behavior of the samples were analyzed using the dependence of the oscillating stress or strain on the angular velocity or frequency. It is shown that the temperature dependences of the storage and loss moduli, as well as the angle of mechanical losses, determine the physical and relaxation transitions in polymers upon their heating. The obtained results can be used in analysis of the effect of conditions of polymer processing on their properties, as well as in optimization of the technological processes of product manufacture and modeling the behavior of materials under operation conditions at the stage of development.

ON THE CRACK PROPAGATION IN STRUCTURAL MATERIALS AND ROCKS FROM THE STANDPOINT OF SYNERGETICS

Purpose: The aim of the work is to analyze from the standpoint of the principles of synergetics the experimental results of the destruction of solid polymers, steels and rocks.Methodology: To analyze experimental data on the propagation of fracture cracks during quasi-static and pulse stretching and bending of samples of solid polymers (PMMA), steels and concrete, taking into account the stock of elastic or elastic-plastic energy at the time of failure. Analyze the shape and quantitative characteristics of dissipative structures that are formed in a solid body when the crack propagates through the material.Findings: Analysis of the distribution modes of county and fast trainings in polymeric materials (PMMA), tool steels and concrete according to different schemes and modes of loading samples shows that the abrupt nature of their movement with periodic trading speed of private or zero is the basis of genealogical organization. The nature of this phenomenon is based on the principles of synergetic, which determine the principle of minimum energy production.Originality: It is shown that the patterns of crack propagation in solid polymers, metals and rocks have a synergistic nature. A working hypothesis on the synergetic mechanism of softening and deformation control of brittle dilatation rocks near underground plants is formulated.Practical implications: It is shown that the nature of the distribution of county cracks during PMMA fracturing, as well as rapid cracks during pulse stretching and bending flat samples of PMMA and the capital as a whole are subject to energy principles, in particular the principle of minimum energy production. It is obvious that for the qualitative and quantitative description of structural changes and destructive deformation of rocks near underground cultivations there is a lack of models of solid environment mechanics. In practice, you need to listen to the abrupt nature of the processes and cooperative effects.