Modification of glass-filled polyamide 66 by reactive oligoorganosilane

Properties of glass-filled polyamide 66 modified by reactive oligoorganosilane were investigated. It was found that modification led to the improvement of the rheological properties of polyamide. The addition of the modifier decreased the glass transition temperature T_g of the polyamide from 60 to 50–59°C, without affecting the melting point. Composites modified by oligoorganosilane are characterized by higher (10–40°C) temperatures of onset and 50% weight loss as compared to the initial composite. It was found that chemical reaction of oligoorganosilane with polyamide and glass fibers took place during coextrusion of the modifier and polyamide, which formed firm chemical bonds between the polyamide and filler and thus favored a considerable improvement in the physicomechanical properties of the composite. The change in the structure and properties of the polyamide observed during modification by oligoorganosilane significantly affected its behavior during friction. The modification made it possible to increase the wear resistance of the composite 1.5 to 2 times and to decrease its friction coefficient from 0.38 to 0.27–0.33. It was also found that the ability of oligoorganosilane to react during its processing with water in the polyamide allowed for a significant decrease in the intensity of hydrolytic processes in the polymer. Because of this, the physicomechanical, rheological, and antifrictional properties of modified composites with an increased content of moisture (up to 3%) in the initial polyamide surpass similar characteristics of the composites containing no modifier, with not only enhanced but also optimum (0.2%) humidity of polymer granules.Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 4, pp. 545–553, July–August, 1998.     

Carbon-Fiber-Reinforced Plastics Based on an Imide Polymerizing Oligomer Binder with a Semi-Interpenetrating Structure

Semi-interpenetrating polymer networks (SIPNs) are synthesized based on a polyimide binder (imide polymerizing oligomer) with addition of polyamide acid. As acylating agents, they include derivatives of benzophenone-tetracarboxylic and diphenyloxide-tetracarboxylic acids and as aminocomponents - diaminodiphenylmethane, diaminodiphenyloxide, and metaphenylene diamine. It is shown that these systems form SIPNs of the snake-in-the-cage type. Uncured compositions forming melts at 300-330°C are used as binders for carbon-fiber-reinforced plastics (CFRP). The homophase structure of the SIPNs in CFRP is shown by dynamic mechanical tests. The interlaminar fracture toughness (G _1c) is measured by the method of a double cantilever beam. It is found that G _1c, as a function of the content (wt.%) of polyamid acid (PAA) in the initial composition used for obtaining CFRP, is of linear character, which is another confirmation of the homophase structure of the SIPNs. The interlaminar fracture toughness achieved for CFRP is 340 J/m² at a 30% PAA content in the initial composition, and the glass transition temperature, which determines the thermal stability of the composites, reaches 320°C. The prospects of employing these plastics in tribotechnics are discussed.     

Rubber wear during friction against a metallic surface (with reference to packing glands for high-speed machine elements)

The wear of rubber in sliding against a metallic surface at high sliding velocities, which causes temperatures at the point of contact of the order of 100–250°C, has been studied. The theoretical equation obtained relates the wear of rubber during sliding against a metallic surface to its elastic-strength and friction properties and to the geometrical characteristics of the metal surface. Satisfactory agreement between theory and experiment is found.Mekhanika Polimerov, Vol. 1, No. 6, pp. 120–126, 1965     

Investigation of the friction of rubber under constant compressive strain conditions at low pressure

A vacuum tribometer was developed which was used to investigate the maximum friction force occurring at the initial instant of slipping in rubber-metal friction pairs under conditions of a given (from 5 to 40%) compressive strain at a low pressure in the temperature range from +100 to –100°C. Filled rubbers on a base of nitrile-butadiene rubbers were studied. Up to the glass transition temperature T_g the vacuum had practically no effect on the maximum friction frocef _m; at temperatures T_g and lower the values off _m obtained in a vacuum were 10–15% higher than those obtained in the atmosphere. It is shown that with a decrease of temperature from 20°C to the glass transition temperature T_g the slope of the dependence of the maximum friction force on the degree of deformation increases, and below T_g decreases. The effect of the slipping speed v on the maximum friction forcef _m was also studied.Laboratory of Polymer Physics, V. I. Lenin Moscow State Pedagogical Institute. Leningrad Branch, Scientific Research Institute of the Rubber Industry. Translated from Mekhanika Polimerov, No. 3, pp. 486–492, May–June, 1970.     

Behavior of filled polyphenylquinoxalines during friction

Conclusion 1. It has been established that, as the chain of polyphenylquinoxalines becomes more rigid by addition of aromatic nuclei of the naphthylimide group to the macromolecule part, the wear resistance of graphite-filled polymer systems increases.2. It has been demonstrated that during friction with filled polyphenylquinoxalines in the polymer binder there occur complex destructive-structurizing processes whose penetration depth is determined by the chemical constitution of the selected polymers.3. It has been established that in the rigid-chain polyphenylquinoxaline during friction at high temperatures, just below the glass-transition point but within the range of faster relaxation processes, the destructive-structurizing processes abate and then at temperatures above 250°C active gelling occurs.Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1049–1054, November–December, 1978.     

Effect of orientation and crystallinty on the friction and wear of polytetrafluoroethylene

A study has been made of the laws governing the changes in wear of polytetrafluoroethylene (PTFE) in relation to the degree of crystallinity and the changes in friction and wear of preoriented PTFE in relation to the working conditions of the metal-polymer friction pair. From the experimental results, conclusions may be drawn concerning the possibility of increasing the wear resistance of polymers by modifying their structural characteristics.Mekhanika Polimerov, Vol. 2, No. 1, pp. 87–92, 1966     

Investigation of the elastic properties of friction plastics with ultrasound

Using data on the rate of propagation of longitudinal vibrations and the dynamic Young's modulus, we studied two-component friction plastics over the temperature range 20–150°C by an ultrasonic pulse method at a frequency of 1 Mc. The changes in acoustic characteristics were investigated in relation to the degree of vulcanization, plasticization and polarity of rubber at 20°C.Mekhanika Polimerov, Vol. 1, No. 2, pp. 152–158, 1965     

A Finite Element Algorithm for Electromechanical Contact Problems

In the last hundred years a lot of work is done in describing and measuring the influence of the pressure on the resistance and wear in electrical contacts. But up to now there exists a lack of knowledge in predicting and optimizing the behavior of electrical contacts with numerical simulation tools considering the pressure dependency. The present work provides a new constitutive model for the contact interface in the case of current flow and a new friction law including electrical wear phenomena. Additionally numerical investigations are made to compare the numerical results with experimental data. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Study of the thermophysical and antifriction properties of polyethylene-based compositions

The mechanical and antifriction properties of polyethylene filled with various, relatively hard fillers are determined. Filling with oxides and silicates produces the greatest increase in wear resistance. The coefficient of friction decreases with increase in the stiffness of the compositions.Mekhanika Polimerov, Vol. 3, No. 6, pp. 1070–1077, 1967     

Effect of normal load on the temperature and velocity dependence of the force of friction for high-elastic materials

The problem of the effect of normal load on the temperature and velocity dependence of the force of friction is examined for rubbers based on SKN-18, SKN-26, and SKN-40. In the temperature range from 18°–100°C the force of friction for these rubbers falls linearly with increase in temperature. The effect of loads up to 10⁷N/cm² on the temperature dependence of the force of friction for SKN-18, SKN-26, and SKN-40 rubbers reduces to a change in the real contact area or an increase in the temperature dependence with increase in load.The velocity dependence of the force of friction for SKN-18 rubber reveals a weak dependence of the activation energy and the average "jump distance" of the molecular chains on specific load. In the low-velocity region the force of friction depends linearly on the logarithm of velocity, at velocities above 0.44 cm/min and pressures of 30×10⁵ N/cm² the force of friction increases sharply due to an increase in uncontrolled heating of the friction surfaces.Mekhanika Polimerov, Vol. 1, No. 4, pp. 123–129, 1965     

Static friction of metal - polymer pairs under vacuum conditions

The static friction of a series of polymer — steel friction pairs has been investigated as a function of the stationary contact time at temperatures from –150°C to +200°C. The experimental technique is described and the results of the experiments are evaluated.Novocherkassk Sergo Ordzhonikidze Polytechnic Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1065–1069, November–December, 1970.     

On the wear of brake pads

Within measurements of brake pads on the IDS high load Tribometer, the wear of pads was investigated by a new non-contact wear measurement under low normal pressures and low temperatures. The first results show that the wear of the pad in the sliding friction is nearly proportional to the friction work, and inversely proportional to the shear strength. The results are also interpreted by the adhesion theory of friction and Archard's equation. On the basis of further interpretations of shear strength and extension of adhesion theory of friction, the wear is derived as a piecewise linear function, which can evaluate explicitly the effect factors of wear and relative correlations at different pressures and different temperatures. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Wear resistance of metal polymer combinations

The possibilities of using polymer protectors in journal bearings are investigated, and the effects of operating conditions on the wear of metal/metal-polymer composition friction pairs are investigated.Mekhanika Polimerov, Vol. 2, No. 4, 580–584, 1966     

Friction properties of highly elastic materials at high contact pressures

A newly designed high-pressure tribometer has been employed to investigate the pressure dependence of the friction force of SKN-40 crosslinked butadiene-nitrile rubber in contact with a steel surface on the pressure range to 1200 kgf/cm² (20°C). Over the entire range of contact pressures the friction process is molecular-kinetic in nature and characterized by a linear dependence of the friction force on the logarithm of the sliding velocity. In the region of normal pressures up to 200 kgf/cm², where the effect of pressure on the friction force reduces to the formation of the actual contact area, the friction constant (proportionality factor relating the friction force and the actual contact area) is practically independent of the pressure. At pressures above 200–300 kgf/cm² the increase in the friction force at fixed actual contact area is attributable to the effect of pressure on the friction constant. The nature of this effect is related not with an increase in the chain-surface interaction energy (the activation energy does not increase), but with an increase in the forces of adhesion owing to the greater number of polymer chain-steel surface contacts on the actual contact area (increase in contact density).Lenin Moscow State Pedagogical Institute, Laboratory for Problems of Polymer Physics. Translated from Mekhanika Polimerov, No. 1, pp. 140–146, January–February, 1971.     

On wheel–rail contact problem with material properties varying with depth

Numerous laboratory experiments indicate that the use of a layer or a coating material attached to the conventional steel body reduce the magnitude of contact stress. Therefore in this paper we solve numerically the wheel–rail contact problem with friction and wear assuming the existence of a small elastic layer on the rail surface. Material properties of this layer are changing with its depth. The friction between the bodies is governed by Coulomb law. In contact zone Archard's law of wear is assumed. We take special features of this rolling contact problem and use so-called quasistatic approach to solve this contact problem. Finite element method is used as a discretization method. The numerical results including the distribution of normal stress along the contact boundary are provided and discussed. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optimization of the composition and tribological properties of high-density polyethylene-calcite-silicon nitride composites by the method of experiment planning

The tribological characteristics (wear resistance, coefficient of friction ) of a high-density-polyethylene-base composite filled with calcite and highly disperse silicon nitride produced by the plasmochemical method are investigated experimentally. The experiment plan was compiled in the form of a simplex lattice, and new points were planned in conducting the experiments. Compositions possessing appreciably elevated wear resistance (by a factor of 500) and a coefficient of friction reduced by 20% as compared with the unfilled polymer were obtained. Institute of Inorganic Chemistry of the Latvian Academy of Sciences, Salasplis, LV-2169. Institute of Polymer Mechanics of the Latvian Academy of Sciences, Riga, LV-1006. Riga Mechanical University, Riga, LV-1050, Latvia. Translated from Mekhanika Kompozinykh Materialov, No. 5, pp. 690–695, September–October, 1996.     

Properties of multicomponent polymers systems

In order to design materials having different mechanical properties combined with a permittivity of 2.2–2.6 and tg =2·10^–4-4.10^–4 at 20±1° C and 10⁶ Hz, it is possible to use compositions consisting of polystyrene, polyisobutylene and polyethylene. Projections of the three-dimensional triangular composition-property diagrams are presented for selecting the composition corresponding to spcified properties (hardness at 20 and 50° C and breaking stress and elongation).Central Scientific-Research Institute of Communications, Moscow. Moscow Krupskaya Regional Pedagogical Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 133–1135, November–December, 1968.     

Antifriction basalt-plastics based on polypropylene

A study is made of the dependence of the mechanical and friction-engineering properties of polypropylene reinforced with basalt fibers on the viscosity of the polymer matrix. It is established that the main factors that determine the mechanical properties of the plastics are the quality of impregnation of the fibers by the binder and the residual length of the reinforcing filler in the composite after extrusion and injection molding. The material that was developed has a low friction coefficient and low rate of wear within a relatively brood range of friction conditions. The basalt-plastics can be used in the rubbing parts of machines and mechanisms subjected to dry friction.Ukrainian State Chemicotechnical University, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov,33, No. 3, pp. 417–421, May–June, 1997.     

Comparative microbiological resistance of various self-lubricating materials

Conclusions 1. Self-lubricating materials of the existing range mostly have low resistance to microbial attack.2. This applies especially to the basic components — Kapron, Kaprolon, fluoroplastic, resin bases without fillers.3. The introduction of fillers and binders modifies the resistance of the basic ingredients; filling fluoroplastics, Kapron, and resins with graphite, coke, metals, or alloys considerably improves the resistance of the self-lubricating compound, whereas using certain organic resins (phenol-formaldehyde, urea-formaldehyde) as binders leads to a fall in the microbial resistance of the lubricating coating.4. Lubricating coatings with silicone or inorganic (including silicate) binders, graphite-filled fluoroplastics and metal-filled graphites, carboplastics, polyarylates, and Maslyanits display the greatest ability to resist microbial attack; these materials are chemically unassimilable by the microbial cell. They can be recommended for use in the tropics without an antimicrobial additive.5. Materials with low resistance under tropical conditions require protection with antimicrobial additives. However, whether or not it is advisable to develop an additive depends in each case on the technical justifiability of using the material in question, its cost-effectiveness, and many other factors. In our opinion, it is not worthwhile developing additives for basic materials (fluoroplastic, Kapron, Kaprolon, certain resins) since there are resistant substitutes available (metal-filled graphite, Maslyanits, AMAN, etc.). As for such a promising material as MFPL, with its unique combination of properties, the search for antimicrobial additives appears to us to be both technically and economically justified.Paper presented at the Third All-Union Conference on Polymer Mechanics, Riga (1976).Kiev Technological Institute of the Food Industry. Translated from Mekhanika Polimerov, No. 6, pp. 1011–1016, November–December, 1977.