Thermofrictional properties of self-lubricating antifriction plastics

New thermally stable polymers (polyimides, polyarylates, and phenolphthalein-phenolformaldehyde copolymers) were used in a study of the thermofrictional properties of their compositions with molybdenum disulfide. We established the existence of several temperature zones of friction and demonstrated their connection with the changes in the relaxation and autohesion properties of the polymers in these same temperature zones.Institute of Organoelement Compounds, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 481–485, May–June, 1970.     

Dispersion of the mechanical characteristics of plastics at various temperatures

The results of an investigation of the dispersion (standard deviation s and coefficient of variation V) of the static and dynamic strengths of plastics are described. The effect of temperature, state of stress, and type of plastic on the dispersion characteristics is considered.Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 29–34, January–February, 1970.     

Some laws of plastics friction

The dependence of the actual contact area S of plastics on temperature, specific load, and sliding speed has been investigated. The value of S increases exponentially with the specific load, the maximum value at large specific loads being less than the nominal contact area. The temperature dependence of S under static conditions between 20 and 130° C is attributable to the decrease in the static modulus of elasticity of the plastic near the glass transition point and to the development of high-elastic and plastic deformations at elevated temperatures. There is practically no change in S as the sliding speed varies from 10^–3 to 10 cm/min; at the same time the force of friction increases slightly.Mekhanika Polimerov, Vol. 3, No. 6, pp. 1078–1081, 1967     

Some characteristics of the strength properties of crystallizing rubbers at elevated temperatures

A study has been made of the reasons for the considerable scatter of the strength properties and the failure of specimens based on crystallizing rubbers outside the gauge length when tested in accordance with Soviet standard GOST 270-53 at elevated temperatures. The relation between the strength distribution and degree of vulcanization is clarified. It is shown that the strength properties of the product are affected by the thermal prehistory of the rubbers.Mekhanika Polimerov, Vol. 2, No. 1, pp. 82–86, 1966     

Effect of lubricating greases on rubber-metal sliding friction at high temperatures

The effect of sliding velocity and temperature on the lubricating action of greases has been investigated under constant and variable temperature conditions. The most important factor is the friction temperature. Two different temperature regions, separated by a change in the type of friction, have been detected. A method has been developed for evaluating the lubricating effect of greases.Scientific-Research Institute of the Rubber Industry, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 876–880, September–October, 1968.     

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     

Effect of antioxidant distribution in polycaprolactam on the variation of strength and deformability at elevated temperatures

The effect of quinhydrone distribution over the cross section on the strength and deformability at elevated temperatures has been investigated for specimens of polycaprolactam. The optimum concentrations of quinhydrone in the surface layer of polycaprolactam retaining maximum strength over an extended period in a hot-air medium have been determined. The most probable areas of formation and localization of structural defects under thermal action have been established.Mekhanika Polimerov, Vol. 3, No. 2, pp. 296–301, 1967     

The influence of imperfections on the creep behavior of woven polymer composites at elevated temperatures

The dynamic behavior of compression molded polymer/woven graphite fiber composites at elevated temperatures is investigated analytically. This is performed with the objective of predicting the initiation of catastrophic failure that may occur after prolonged usage of the material at these temperatures. Special attention is paid to the behavior of the voids present in them where the failure may occur. The polymer matrix is modeled as a 4-parameter model (Maxwell-Voigt combination) (Govindarajan et al., in: Advances in Computer-Aided Engineering, ASME, 1994) while the composite structure is modeled using the fiber undulation model (Ishikawa and Chou, J. Mater. Sci. 17, pp. 3211–3220, 1982). The relation between the polymer properties and the ambient temperature is modeled after Arhenius' relation (Govindarajan et al., 1994; Ferry, Viscoelastic Properties of Polymers, Wiley, New York, 1961). The multiple phases in the matrix are taken into account through Eshelby's theory (Proc. Royal Soc. London A 241, pp. 376–396, 1957) and its extension for multiple occurrences of the same phase (Tanden and Weng, Polymer Composites 5, pp. 327–333, 1984; Weng, Internat. J. Eng. Sci. 22 (7), pp. 845–856, 1984) which assumes an ellipsoidal shape for inclusions. The resulting elastic equations are transformed into the time domain using Laplace transformation and the correspondence principle (Govindarajan et al., 1994; Wang and Weng, ASME J. Appl. Mech, 1992). All the voids are considered to be prolate ellipsoids with the 1-axis being the axis of symmetry. The distribution of voids is assumed to be of a Gaussian form with respect to the aspect ratio. The response of the composite under creep condition (constant load) has been simulated. Relations between the applied stress and the stresses in the matrix/void phase are also supplied, so that the influence of the voids may be characterized. The model is then applied to simulate the behavior of an epoxy/woven graphite composite to obtain the numerical results.     

Behavior of rigid plastics under cyclic loading

Research progress on the dynamic fatigue of plastics is briefly reviewed. Attention is concentrated on the problems of damage accumulation and self-heating. The effect of various factors on the fatigue of plastics is considered. The possibility of predicting the cyclic life-time from the results of long-time static strength tests is examined. The prospects for the construction of a theory of fatigue strength in complex states of stress are weighed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 97–107, January–February, 1969.     

Cold flow and melting of plastics under severe friction conditions

Dry friction of a series of crystalline polymers (polypropylene, nylon, PTFE) against steel over a wide range of sliding velocities (4.4–4.4×10^–4 cm/sec) and loads (P=7.5–360 kg) with almost complete mutual overlap of the friction surfaces is studied. It is shown that friction of polymer materials against steel may be accompanied by melting of the crystalline polymer (at high velocities) or cold flow (at low velocities) in the surface layers associated with an orientation effect and the appearance of anisotropy.Mekhanika Polimerov, Vol. 1, No. 5, pp. 95–100, 1965     

Investigation of the transfer process in polymer friction

It is shown that infrared spectroscopy can be used to investigate material transfer in external polymer friction. The kinetics of the process of transfer of Teflon to a polyethylene surface are examined and it is shown that the thickness of the transferred layer depends on the conditions under which the rubbing pair operates.Institute of Mechanics of Metal-Polymer Systems, Academy of Sciences of the Belorussian SSR, Gomel'. Translated from Mekhanika Polimerov, No. 4, pp. 750–752, July–August, 1971.     

Determination of the static strength of plastics from the elasticity and internal friction characteristics

It has been shown experimentally that the tensile or compressive strengths of various plastics on a broad temperature range can be estimated from the values of the dynamic modulus of elasticity and logarithmic decrement measured by a vibration method.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 551–554, May–June, 1976.     

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.