Compression Relaxation of Multi-Structure Polymer Composites in Penetrating Liquid Medium

Abstract

Multi-structural polymer composites are widely used in the mechanical engineering, automotive, aviation and oil refining industries, as well as in the printing industry as a shock-absorbing deckle on the offset cylinders of printing machines. During offset printing, composites come into contact with inks and washing solutions, the components of which penetrate the material and cause the polymers to swell. This process degrades the print quality, and for this reason the study of its features is relevant. The prerequisites for this work are the study of the fundamental laws of diffusion and sorption of liquids by polymers with different micro- and macro-structures in different physical states and in different forms (e.g., films, sheets, fibers and fabrics). The combination of polymer materials in the composition of multi-structural fabric blankets makes it possible to obtain materials with unique mechanical properties and high resistance to liquid penetrating media and to use them in high-tech processes of multi-color printing with high resolution and color rendering. This article reports for the first time the kinetics and thermodynamics results obtained from the swelling of multi-structural polymeric blankets in solvents used in printing, and the effect of sorption of different polar liquids on the viscoelastic strain under compression during the operation of the damping systems of printing machines. Using mathematical models of activated liquid diffusion in polymers and deformation of a viscoelastic body, the swelling rate constants, solvent diffusion coefficients (the kinetic characteristics of the swelling process) and Flory–Huggins parameters (the thermodynamic characteristics of the interaction of the solvent with the composite) for composite–solvent systems with several chemical composition variants were determined. The elastic modulus and the viscosity coefficient of the composite under liquid saturation were calculated based on the experimental cyclic compression data. The range of change in the compression and restoration times of the polymeric blankets (0.09 s ÷ 0.78 s) was determined. It was shown that the composite swelled to a limited extent in all the studied liquids. All solvents used were thermodynamically poor (χ > 0.5). It has been established that rubber–fabric blankets coated with nitrile rubber are the least resistant to the action of dichloroethane, and that blankets with layers of polyolefins are not resistant to ethyl acetate. Water significantly affects the physicochemical properties of rubber–fabric blankets with a large proportion of cotton fabric layers. The data obtained can serve as a basis for optimizing the compositions of inks and cleaning solutions, as well as a theoretical basis for the thermodynamics of composite–solvent systems.

Production and properties of electrically conductive polymer composites reinforced with cotton threads

“…This is the well-known Patrikeev-Mullins effect, 42 which has significant features in the cyclic deformation of composites with reinforcing fibers. 43 During stretching, the stress in the composite increases monotonously and can be described by the linear equation with a constant conditional modulus of elasticity in Figure 8. When unloading, the stress change can be described by the two moduli, small in the 0%-15% strain range and large over 15% strain.…”

Thermodynamics of solvent sorption by layers of carbon-chain polymers in damping rubber blankets

“…Table 1 presents the thermodynamic properties of the composite-solvent system obtained by studying the swelling kinetics of two rubber blankets in liquid medium. The table summarizes the values of the Flory-Huggins parameter χ calculated using equation (1), and the swelling rate constant k calculated based on the slope of the straight line tangent shown on the sorption kinetics graphs plotted in semi-log coordinates ln(α ∞ /α ∞ −α) versus t given in previous publications [14]. On the graphs and in the table, α ∞ denotes the maximum swelling index determined by the sample mass α.…”

“…These are the most durable rubber composites designed for offset printing. The structure and thickness ratio of the rubber layers and reinforcing blankets are described in detail in [14].…”

“…In [14], the deformation and sorption properties of composites in liquid medium as a whole were studied using the Kelvin-Voigt viscoelastic model. In order to obtain the swelling patterns and predict the variation of the mechanical properties of polymer composites in liquid medium, it is nessesery to know the thermodynamic properties of the rubber-solvent systems, i.e.…”