Plasma Modification of Elastomers

The treatment of elastomer articles in a low-temperature glow-discharge plasma in fluorinated organics is an effective method for the enhancement of their wear resistance without changing the formulation of rubbers. As a result of plasma-assisted deposition on an elastomer of a fluorinated antifriction film chemically bound to the substrate, the elastomer friction coefficient is considerably decreased, sticking to a counterface is prevented, and the wear resistance of the elastomer is enhanced, retaining their bulk properties. Based on the study of the structure of the antifriction film at different modification stages and its transformation during friction, a conclusion on the mechanism of elastomer surface failure under dynamic friction conditions was made.     

Thermal Polymerization of Styrene Sorbed from the Gas Phase into Polymer Films as a Method for Synthesizing Precursors of Ion-Exchange Membranes

Russian Journal of Electrochemistry - Abstract—The thermal polymerization of styrene sorbed from the gas-phase into polymer films of polyvinylidene fluoride (PVDF) is carried out at...     

Carbonization of polytetrafluoroethylene surface by UV-induced grafting of vinylidene chloride

A method has been developed for modifying the surface layer of polytetrafluoroethylene by incorporation of poly(vinylidene chloride) via UV radiation-initiated graft polymerization of vinylidene chloride from the vapor phase using a PRK-4 mercury lamp. By the subsequent treatment of the composition with aqueous ammonia, dehydrochlorination (carbonization) of the grafted poly(vinylidene chloride) has been performed. The kinetics of UV grafting and the distribution of the carbonized phase in the polytetrafluoroethylene matrix have been studied. A material with the carbonized surface layer of a 10—30 μm thickness and a contact angle of about 57° remaining stable over time has been obtained.     

Synthesis of polymer nanocomposite ion-exchange membranes from sulfonated polystyrene and study of their properties

Methods for the preparation of composite ion-exchange membranes from polymer (polyvinylidene fluoride (PVDF), ultrahigh molecular weight polyethylene (UHMWPE), and polypropylene (PP)) matrices were considered. Polystyrene (PS) was introduced in the matrices by thermal polymerization of the monomer followed by sulfonation of the implant. The fundamentals of membrane synthesis from industrial polytetrafluoroethylene (PTFE, Teflon F-4) films by thermal polymerization of styrene in a film stretched in a monomer solution followed by sulfonation of incorporated PS were described. The literature on radiation- chemical synthesis of composite ion-exchange membranes based on polymer matrices with embedded polystyrene and its subsequent sulfonation was analyzed. Some problems of the kinetics and mechanism of thermal implantation of PS into various polymer matrices under different conditions were discussed. The physicochemical characteristics, structure, and transport properties of the membranes synthesized by thermal implantation of PS were reported. The obtained membranes were tested in low-temperature fuel cells.     

Decomposition of pentaammineaquacobalt(III) perchlorate under laser radiation action

Photolytic decomposition of the complex [Co(NH₃)₅(H₂O)](ClO₄)₃ under the action of a laser with a wavelength of 355 nm, which is resonant in energy to the energy of the (¹ A _1g → ¹ T _2g ) d–d transition, was studied. Decomposition of the complex is accompanied by a release of ammonia with its subsequent oxidation to nitrogen oxides and by partial cobalt reduction with the formation of the mixed cobalt(II, III) oxide Co₃O₄.     

Synthesis and transport properties of proton-conducting membranes based on polyvinylidene fluoride films with introduced and sulfonated polystyrene

Thermal polymerization of styrene sorbed into a polyvinylidene fluoride (PVdF) film from a toluene solution followed by sulfonation of the resulting material was performed. The kinetics of polystyrene (PS) accumulation in the PVdF film during thermal polymerization was studied. Samples with 6–30 wt % PS and ∼100% PS sulfonation were obtained. Proton-exchange membranes wsith an ion-exchange capacity of up to 2 mg-eq/g and proton conductivity of up to 0.008 S/cm at 75% relative humidity were prepared. The permeability coefficients of water, methanol, and hydrogen and their dependences on the amount of introduced PS, ion-exchange capacity, and water uptake of membranes were measured. The synthesized materials proved similar to MF-4SK membranes in their basic transport characteristics and can be used as proton-exchange membranes in hydrogen-air and alcohol fuel cells.     

Investigation of poly(vinylidene chloride) distribution in perfluorinated cation-exchange membranes MF-4SK upon UV- and γ-initiated graft polymerization

A new process for grafting poly(vinylidene chloride) (PVDC) to the membrane material MF-4SK by UV-initiated graft polymerization of the monomer from the gas phase has been developed. Modified membranes containing up to 20 wt % of UV-grafted PVDC have been obtained. Microphotographs of thin sections of the modified membranes have been investigated. It has been shown that the pretreatment of the membranes and variation of UV- or γ-grafting conditions make it possible to achieve an uniform distribution of grafted PVDC both along the thickness of the membrane and in a thin surface layer. The values of the parameters determining the character of the distribution have been estimated. Numerical simulation of the UV- and γ-initiated graft polymerization of VDC gave solutions for the grafted-PVDC distribution fitting with the experimental data.     

Modeling of the impurity distribution obtained by ion implantation

Models and a suite of programs (TRION, PIRSON, CHAPS, and DYCOD) that make it possible to calculate the impurity distribution for any implantation dose in a target with arbitrary composition are described. Test calculations for each program showed that the results are in good agreement with experimental data and with theoretical calculations performed by other authors. The suite of programs is intended for the development of the physical principals of ion-beam technologies.Translated from Izvstiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 5, pp. 8–22, May, 1994.     

Polytetrafluoroethylene modification by radiation grafting of vinylidene chloride and its dehydrochlorination

A process has been designed for manufacturing a new composite material consisting of a PTFE matrix with a carbon phase implanted in the surface layer of up to 30 μm thickness. The process involves radiation graft polymerization of vinilydene chloride (VDC) from the vapor phase onto the PTFE matrix followed by dehydrochlorination of implanted PVDC. The VDC grafting kinetics, the distribution of the grafted polymer and the carbon phase, and the mechanical characteristics of the composite material have been investigated. It has been shown that unlike initial PTFE, the composite possesses good adhesive bonding properties and a small contact angle.