V. G. Nazarov

Simulation of sulfonation and structure of surface layer in polyethylene

A mathematical model of sulfonation of an HDPE film by sulfuric anhydride from gaseous is proposed. This model takes into account changes in the physicochemical characteristics of the sulfonated layer in the course of modification. It is assumed that this process is controlled by an increase in the solubility and diffusion rate of sulfuric anhydride during sulfonation. An approximation equation for the description of sulfonation kinetics and conversion is derived. Calculated data agree with the experimental results. This model is used to calculate the depth of sulfonation of an HDPE film with allowance for its amorphous-crystalline structure. Morphological changes in the sulfonated PE surface layer are studied by electron microscopy.

Transformation of the modified layer of fluorinated polyolefins under stretching

The stress-strain properties of the fluorinated layer of polyolefin films are estimated. A comparison of the elastic moduli of fluorinated and original film samples of LDPE and HDPE shows that the surfacefluorinated films of polyolefins can be assigned to “rigid coating on a soft support” systems. Deformation of these multilayer films leads to a special type of superficial gelation with a characteristic regular relief. With allowance for this relief, it is possible to calculate the ultimate stress of the fluorinated layer for LDPE and HDPE films.

Comparative study of the influence of polyethylene film surface modification on interaction with blood components

A comparative study of how modification of polyethylene film surfaces performed by plasmachemical treatment and chemical modification by sulfonation and fluorination influence the interaction with blood components is performed. In order to vary the depth and intensity of the impact on the polyethylene surface during processing, the duration of treatment is varied, while the other optimal parameters of the modification process are constant. The characteristics of the polyethylene surface, such as the wetting angle by water, surface energy, surface morphology, that change during treatment are determined. It is shown that these changes have a symbate behavior. The influence of polyethylene treatment on the hemocompatibility parameters of modified surfaces, such as the degree of hemolysis induced by contact with a foreign surface, the number of adhering platelets, and the degree of their activation, is studied. All three investigated modification methods show the possibility of significant improvement of the hemocompatibility parameters, but the most promising method is the method of surface fluorination that provides the maximum increase in the hemocompatibility properties and allows one to modify finished products of various shapes and sizes.

Nanostructural encapsulation of iodine in polyvinyl alcohol

The process of obtaining high-molecular inclusion compounds of polyvinyl alcohol (PVA) doped with iodine upon exposing aqueous solutions of the polymer to vapors of crystalline iodine in normal conditions is studied. It is visually recorded that the initially colorless aqueous PVA solution turns dark blue, then black, and acquires a gel-like consistency. If potassium iodide (1–10 wt %) is present in an aqueous PVA solution, the gel is transformed into a tight jelly and this transformation is accompanied by syneresis and leads to significant shrinkage (up to 40%) of the gel. It is established that the content of iodine in the jellies depends on the initial concentration of potassium iodide in a PVA solution and reaches significant values. When subjected to drying, the jellies form dyed-black film samples containing iodine, which does not actually sublimate from them during a long shelf life. The iodine content in jellies and dried samples of PVA can reach 75% of the polymer’s dry weight in some cases. Potential fields of applications for iodine-containing polyvinyl alcohol matrices are pharmaceuticals, medicine, and veterinary science, including their application in transdermal therapeutic means.

Mechanical Properties of Composite Materials Based on Latex-Impregnated Needle-Punched Nonwoven Fabrics from Fibers of Different Nature

The influence of the chemical nature of fibers on mechanical properties of nonwoven needlepunched fabrics impregnated with latex-based copolymer based on butadiene and methyl-acrylic acid (SKD-1) was studied. Fabrics made of traditional polyester and polypropylene fibers and polyacetal fiber were used for impregnation. Application of fabrics made of polyacetal fiber provides impregnated materials with maximum tensile strength. The chemical nature of fibers does not influence the strength of the impregnated materials.

Special features of surface fluorination of thermoplastic polyurethane elastomers and its effect on the polymer properties

Special features of fluorination of thermoplastic polyurethane elastomers (TPE) are considered. A dependence of the fluorination level of TPE on the fluorination time and the atomic structure of the modified surface layer is detected. A significant effect of fluorination on the surface morphology of TPE, its physical and mechanical properties, flammability, and resistance to fuels and lubricants is determined and studied. The surface morphology of a fluorinated sample in comparison with a virgin one becomes more developed owing to the emergence of a high-frequency component. The formation of this structure is determined by a more intense fluorination of elastic, less dense polymer regions, to large depth and with partial destruction. A decrease in the swelling rate of the samples in aviation kerosene and motor oil is shown. It was found that surface fluorination reduces flammability of the thermoplastic elastomer with respect to such indicators as ignition time, burning-out height, and maximum flame height. In general, according to the Federal Aviation Regulations FAR-25, fluorination of thermoplastic elastomers shifts them from the category of “burning” into the category of “self-extinguishing.”

Modeling the directed diffusion of fluid through the microchannels on the surfaces of polymer films

The heterogeneous surface gradient micro- and macrostructures of various designs, including extensive channels, were analyzed on films of low-density polyethylene formed through the serial treatment with fluorinating and sulfuring reagents in combination with mechanical modification. Approaches to the development of systems for the directed microfluidic transfer of target compounds on film surfaces by “molecular rail channels,” which is based on significant differences in the physicochemical properties of modified regions, were discussed. A mathematical model of mass transfer through the gradient surface structures of a given chemical and structural design was developed to estimate the possibility of their use for the directed transfer of target compounds.

Structuring in poly(vinyl alcohol)-potassium iodide-iodine systems: Small-angle X-ray-scattering study

The sizes of supramolecular density fluctuations in gels and solid films obtained during formation of iodine inclusion compounds in an aqueous solution of poly(vinyl alcohol) are studied via small-angle X-ray scattering. It is shown that, in the case of iodine-containing poly(vinyl alcohol) samples prepared through drying of iodine-containing gels, several diffraction peaks that are related to the long-range order in the packing of structural fragments manifest themselves. The presence of the peaks indicates periodic density fluctuations in the packing of polymer chains with a period of 1.34 nm and a coherence length of 18.0 × 0.5 nm. The equidistance of peaks in units of scattering-vector modulus makes it possible to suggest the formation of layered systems, that is, systems with a single well-defined repeat period, during gel drying. Wet samples of the iodine-containing gel based on poly(vinyl alcohol) do not reveal any ordering. Heterogeneities in the structure of iodine-free gels may be regarded as voluminous structures with free cavities that survived after the extraction of iodine. These cavities in gels may be again filled with iodine or other complementary molecules.

Modeling of Sliding Friction Processes in Surface/Spatial Modified Elastomer-Metal Couple

This article discusses theoretical approaches to improvement of antifriction properties of rubbers by means of application of an optimal combination of methods of their spatial and surface modifications. The first model involves formation of an interconnected network system of ingredients in the form of spherical particles with a low friction coefficient imbedded in the elastomer surface layer (including modified one). It is demonstrated that, in this case, areas of reduced friction appear under the action of a normal load, and these areas even at an insignificant concentration of spherical particles result in a significant decrease in the overall sliding friction coefficient of the surface-modified elastomer. The second model implies addition of nano- and microcapsules to the surface layers of the elastomer, containing fluorine and other antifriction components in the liquid phase. In this case, the loss of antifriction component due to migration processes is eliminated in the rest state, and in operation of the friction assembly, the microcapsules are destroyed in a controlled way under the load action with respective discharge of lubricant to the surface.