Role of diffusion in the formation of adhesion bonds between polymers

So-called "direct" proofs of self- and mutual-diffusion in the formation of adhesion bonds between polymers [3] are discussed critically. It is shown that in reality none of these direct proofs can be regarded as such. Accordingly, the question of the validity of the diffusion mechanism of adhesion as applied to thermodynamically incompatible or only "partly compatible" polymers remains open.Mekhanika Polimerov, Vol. 3, No. 5, pp. 850–853, 1967     

Direct proofs of self- and mutual diffusion in the formation of adhesion bonds between polymers

The authors discuss experiments aimed at the direct investigation of self- and mutual diffusion in polymers. New electron microscope data are presented for mutual diffusion in the systems polyvinyl chloride — polymethyl methacrylate, polyvinyl chloride — polybutyl methacrylate, and polystyrene — SKS-85. It is shown that with increase in temperature and improvement in compatibility the depth of mutual diffusion increases. The data obtained make it possible to calculate the polymer-polymer diffusion coefficient.Mekhanika Polimerov, Vol. 2, No. 3, pp. 446–452, 1966     

Local compatibility and the adhesion of polymers

The role of the thermodynamic factor in creating an adhesion bond between partly or wholly compatible polymers is discussed. The importance of this factor depends on the fact that polymers brought into contact will diffuse into each other only if they are wholly or partly mutually soluble. This mutual solubility is confined to a surface layer and is determined by the local diffusion. In considering the mechanism of formation of an adhesion bond between two polymers it is necessary to take their surface properties into account. In the diffusion theory of adhesion diffusion is regarded as the motive force in the creation of an adhesion bond.Moscow Lomonosov Institute of Fine Chemical Technology. Translated from Mekhanika Polimerov, No. 3, pp. 455–459, May–June, 1969.     

Reversible changes in the adhesion of polymers to solid surfaces

The adhesion of low-density polyethylene to steel and glass changes when water and acid molecules penetrate to the polymer-substrate interface. Their removal leads to total or partial recovery of the initial adhesion. An adhesive bond between polyethylene and the substrate was observed at room temperature as well as at 50° C. The results are explained in terms of the dynamic adsorption-desorption behavior of polyethylene adhesion. It is suggested that the adhesion is based is based on the van der Waals interaction between the substrate and the polar surface groups of the polymer.Mekhanika Polimerov, Vol. 4, No. 2, pp. 309–313, 1968     

Effect of hydrostatic pressure on submicrocrack formation in oriented polymers

Small-angle x-ray scattering has been used to obtain a quantitative estimate of the concentration and size of the submicrocracks in Kapron and polypropylene equally extended at 1 and 1500 atm. Direct evidence of the retarding effect of pressure on fracture development has been obtained.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga: Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 917–921, September–October, 1971.     

Reversible changes in the adhesion of polymers to solid surfaces

The adhesion properties of coatings of polycrystalline hexafluoropropylene—vinylidene fluoride copolymer on steel and glass have been investigated. Coatings formed at 200–240° C suffer a reversible loss of adhesion following the diffusion of water and acid molecules to the interface, which is attributable to the mobile adsorption-desorption nature of the adhesion of this particular copolymer to steel and glass. Heat treatment at 280° C gives the coating improved resistance to the debonding action of water.Ural Scientific-Research Chemical Institute, Sverdlovsk. Moscow Institute of Fine Chemical Technology. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1065–1070, November–December, 1968.     

Strength and deformability of reinforced polymers in tension normal to the fibers

The strength and deformability of reinforced polymers in tension across the fibers is investigated. It is assumed that the polymer deforms as an ideal elastoplastic body. Relations are obtained for the nature of the deformation of the polymer between the fibers and the strength and deformability of the composite with allowance for the structural distribution of the components. Theoretical stress-strain diagrams are presented for composites with different reinforcement densities and resin elasticities. The theoretical values of the strength and deformation of reinforced polymers with the load applied across the fibers are compared with the results of experiments on model specimens of epoxy-Thiokol polymers.Leningrad Mechanical Institute. Translated from Mekhanika Polimerov, No. 4, pp. 682–687, July–August, 1970.     

Formation of the adhesion bond between polyethylene and solids

When a coating of low-density polyethylene on steel or aluminum is heat-treated, the adhesion strength increases linearly from zero to values exceeding the strength of the film. This is caused by the metal-catalyzed oxidation of the polymer in the contact zone by oxygen diffusing through the film.Ural Scientific-Research Chemical Institute, Sverdlovsk. Translated from Mekhanika Polimerov, No. 5, pp. 932–934, September–October, 1970.     

Effect of submicroscopic crack formation and relaxation phenomena in polymers

The development of submicrocracks and the changes taking place in their concentration during loading and unloading cycles were studied by the low-angle x-ray scattering method in oriented amorphous-crystalline polymers (capron and polypropylene). The deformation () of the polymers was compared with the changes in submicrocrack concentration (N_cr).A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 387–392, May–June, 1970.     

Determination of the shear strength of the metal-plastic adhesion bond and its response to lubrication

A new method of determining the shear strength of the metal-plastic adhesion bond is considered. Experimental data on its dependence on load and indenter dimensions are presented for various types of plastics under different conditions.State Scientific Research Institute of Machine Science, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 854–858, September–October, 1970.     

Effect of formation conditions on the supermolecular organization and mechanical properties of polyethylene film

Films formed by extruding medium-pressure polvethylene through a flat-slot have a spherulitic supermolecular organization whose principal parameters (size and shape of the spherulites) are determined by the extrusion conditions. Thus, as the draw-down ratio increases, the radius of the spherulites decreases, and their degree of flattening relative to the direction of extension increases. Stretching these films leads to a transition from a spherulitic to an orientational supermolecular order, whose period is genetically related to the diameter of the starting spherulites. Films containing flattened spherulites have a yield point anisotropy opposite in sign to the degree of flattening. The mechanical anisotropy, like the degree of flattening, increases with increase in the draw-down ratio. The probable cause of flattened spherulite formation is the draw-down process, whose mechanical field may retard the radial growth of the spherulites in the take-off direction.Institute of High-Molecular Compounds, Academy of Sciences of the USSR, Leningrad. Scientific-Research Institute of Polymerization Plastics, Leningrad. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 207–212, March–April, 1969.     

Effect of hot-drawing conditions on the orientation characteristics of carbon-chain fibers determined by the acoustic method

The orientation characteristics of polypropylene, polyacrylonitrile, and chlorinated PVC fibers, determined by the acoustic method, have been investigated in relation to the fiber drawing conditions (draw ratio, speed, and temperature). It is shown that there is a correlation between the mechanical characteristics and the degree of acoustic anisotropy.Tashkent Institute of the Textile and Light Industries. Translated from Mekhanika Polimerov, No. 3, pp. 552–554, May–June, 1971.     

Molecular destruction of polymers at the apex of a major crack

We employed infrared spectroscopy and infrared spectroscopy of deflected total internal reflection to study the rupture of polymer macromolecular chains (polyethylene and polypropylene) at the apex of a growing crack. It was shown that the break concentration at the crack surface is of the same order of magnitude as the total concentration of chemical bonds in the polymer; molecular rupture occurs not only at the apex itself but also at some distance from it. The dependence of the break concentration on the distance from the crack apex was measured. The observed patterns were related to the experimentally determined external-load distribution function for individual chemical bonds near the crack apex.I. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 4, pp. 621–625, July–August, 1972.     

Mechanical properties of polymers at 4.2°K and their dependence on chemical structure and the conditions of physical structure formation

Values of the modulus of elasticity, proportionality limit, and fracture strains and stresses have been measured at 4.2°K for polymers with different chemical structure and for a series of physically modified polymers. Relations have been established between the cryogenic values of the mechanical properties, the chemical structure of the macromolecules, and the conditions of formation of the physical structure of the polymer.     

Effect of the conditions of formation of glued joints on their thermophysical properties

A correlation has been experimentally established between the thermal resistance of adhesive films and the internal stresses that develop during the curing process. During cure the thermal resistance varies in parallel with the internal stresses. It is assumed that the development of thermal resistance is determined by the tension produced in the film by the development of the internal stresses.Voronezh Forest Engineering Institute. Translated from Mekhanika Polimerov, No. 4, pp. 754–756, July–August, 1973.