Elasticity of the intercrystallite zones and the mechanical properties of oriented polymers

As a result of a study of the behavior under load of the elements of the supermolecular structure of oriented amorphous-crystalline polymers it is shown that the stresses on the crystallites and the amorphous zones in series with them in the direction of the chain axes are equal to the mean stress applied to the specimen along the orientation axis. The nature of the elasticity and deformability of the amorphous zones is analyzed. A relation is obtained between the strength properties of oriented polymers and the number of load-carrying chains in the amorphous zones.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 1002–1007, November–December, 1969.     

Polymer fractography and fracture kinetics

The fractographic method makes it possible to determine the test temperature and time at which anomalies appear in the temperature-time dependence of the strength of polymethyl methacrylate and polycaprolactam by finding the conditions of disappearance of specular zones from the fracture surfaces of these polymers. For PMMA these values are –40°C and 10^–2 sec, for PCL –120°C and 10^–7 sec, respectively.For communication 1 see [2].Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 232–237, March–April, 1971.     

Effect of temperature on the nature of the tear surface of styrene polymers

The tear surfaces of polystyrene and SKS-85 butadiene-styrene copolymer (85% styrene) have been investigated at temperatures from –45 to +100°C and from –60 to +40°C, respectively. The fracture surface of these polymers changes not only on transition from the glassy to the high-elastic state, but also within the glassy state itself, changes being observed both in the relative extent of the individual zones contributing to the fracture surface and in the nature of those zones. Changes in the nature of the fracture surface associated with a slowing of the fracture process occur at 0 and 40°C in the case of polystyrene and at –10°C in the case of copolymer SKS-85 and are attributable to secondary transitions in the polymers.Moscow Technological Institute of the Meat and Dairy Industry. State Institute of Polymer Adhesives, Kirovakan. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 257–264, March–April, 1969.     

Temperature dependence of the mechanical properties of polymers of different chemical structure in the temperature range from 4.2 to 300°K

Conclusions 1. The temperature dependences obtained for the ultimate alongation, tensile strength, and elastic modulus of various polymers showed that the relationship between the mechanical properties and chemical structure of macromolecules found in our earlier work at 4.2°K is retained at 78°K and, possibly, up to 90°K.2. It was shown that the passage of the tensile strength through a maximum upon warming from 4.2°K results from a corresponding increase in deformability, which is accompanied by a decrease in the elastic modulus and deviation of the polymer bodies from Hooke's law progressively with increasing temperature.3. It was shown that the amorphization of crystallizing polymers, for example, by quenching, gives a marked change in the deformability, tensile strength, and elasticity of the polymer body over the entire range from 300 down to 4.2°K.4. Study of the mechanical properties of polymers at 78°K in a helium medium and liquid nitrogen showed a marked effect of contact of the polymer with liquid nitrogen on these properties. This effect is different for polymers of varying chemical structure as well as for the same polymer in different physical states.Report presented at the Third All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1976.L. Ya. Karpov Scientific-Research Institute of Physical Chemistry, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 387–391, May–June, 1977.     

Self-heating of plastics during cyclic defformation

Analysis of the phenomenon of self-heating as a result of competition between hysteresis heating and heat losses to the ambient medium shows that for polymers two zones of steady-state heating are possible: a low-temperature zone, corresponding to a high endaurace limit, and a high-temperature zone, corresponding to low endurance. Between these zones is a temperature region in which steady-state heating is impossible. The high-temperature steady-state zone is frequently not realized as a consequence of the sharp drop in strength at high temperatures. The transition from one steady-state zone to the other is discontinuous, the occurrence of one or the other zone being determined by the deformation conditions (stress, cycling speed, size of specimen, heat conductivity, etc.). However, the self-heating temperature at which this transition takes place does not depend on the deformation conditions, but is determined only by the properties of the material. These conclusions have been confirmed experimentally.Mekhanika Polimerov, Vol. 1, No. 3, pp. 93–100, 1965     

Increasing the adhesion of polymers to metals by adding substances with conjugation systems

The electron-donor properties of polymers with conjugation systems (PCS) and their capability of forming -complexes with metals is of interest in relation to adhesion. Small amounts (0.01–0.1%) of substances with polyconjugation systems (polydiphenylbutadiene, polyphenylacetylene, and copolymers of naphthalene and anthracene with benzene) increase the adhesion between aluminum and polymers used as electrical insulation coatings (polyesters, polyimides, and their derivatives). With optimum PCS dosage, the resistance to peeling rises by 15–38%.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 365–367, March–April, 1974.     

Elastic properties of certain polymer matrices at low temperatures

A study is made of the viscoelastic behavior of the polyimide DFO and polybenzoxasol (PBZ) at low temperatures. Pulsed ultrasound is used to measure ultrasonic velocity in polymers at the frequency f=5 MHz within the temperature interval 4.2–240 K. Data obtained from acoustic measurements is used to calculate the dynamic elastic modulus, shear modulus, compressive bulk modulus, Poisson's ratio, and certain thermophysical characteristics (Debye temperature, specific heat, coefficient of linear expansion, Grünheisen parameter). It is established that the investigated polymers have low dynamic moduli at 4.2 K. Their values change by 18–20% within the temperature range 4.2–240 K. The polymers also have a large free volume at the temperature of liquid helium. The results show that polyimide DFO and PBZ have good service properties at low temperatures.Paper presented at the IX International Conference on the Mechanics of Composite Materials, Riga, October, 1995.Moscow State Academy of Automotive and Tractor Engineering, Russia. Translated from Mekhanika Kompozitmykh Materialov, No. 4, pp. 454–459, July–August, 1996.     

Prediction of the short-term strength of polymer materials based on equations of state

The possibility is analyzed of using equations of state for predicting the mechanical properties of linear amorphous polymers with short-term loading from data for their compressibility.D. I. Mendeleev Chemical Technology Institute, Moscow. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 2, pp. 258–262, March–April, 1997.     

Strength properties of oriented amorphous linear polymers in relation to their structure

Tensile tests have been conducted at room temperature on uniaxially oriented films of a number of amorphous linear polymers. It has been shown that the mechanical properties of the oriented polymers in the glassy state are chiefly determined by two parameters of the structure—the degree of orientation of the macromolecule segments and the concentration of stressed chains per unit volume, irrespective of the molecular weight of the polymer and the orientational stretching conditions.Mekhanika Polimerov, Vol. 3, No. 3, pp. 455–460, 1967     

Multifactor investigation of the process of polymer wear in the thermally stressed state

Conclusions 1. The temperature regime and stress in the surface layers of polymers exert the most significant effect on wear intensity.2. The effect of these factors is displayed via a change in contacting conditions and the complex of mechanical properties of the polymeric materials.3. The effectiveness of using statistical methods of experiment planning has been revealed in studying the wear process, and also in studying the change in mechanical properties from the action of temperature factors: Reliable mathematical models have been obtained which connect up hardness and wear intensity with temperature regimes.A report presented at the Third All-Union Conference on Polymer Mechanics, Riga, 1976.Rostov-on-Don Institute of Railroad Transport Engineers. Rostov Agricultural Engineering Institute. Translated from Mekhanika Polimerov, No. 1, pp. 67–72, January–February, 1978.     

Supermolecular structure and properties of polymers

Questions relating to methods of obtaining supermolecular structures and their effect on the properties of polymers are considered.Presented at 2nd All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1971.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 409–415, May–June, 1972.     

The piezoelectric effect in polymers

A series of polymers with varying polarity and chain rigidity has been investigated. On the basis of the results obtained it is concluded that piezoelectric properties are to be found in polarized polymers with small dipole groups and a rigid chain due to their polarity.Mekhanika Polimerov, Vol. 4, No. 1, pp. 169–172, 1968     

Instability of the crystallites in oriented polymers under load

Large-angle x-ray diffraction and infrared spectroscopy have been used to investigate the behavior of the crystalline zones in oriented polymers under load. It is shown that under the influence of a load applied along the axis of orientation the crystallites are partially destroyed, the more so the greater the applied stress. For different polymers the destruction of the crystallites is the greater the weaker the intermolecular bonds. The stability of the crystallites is improved by orientation.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 516–520, May–June, 1976.     

Friction properties of physically modified polymers

The effectiveness of using physical methods of modifying the surface layers of polymers in order to improve their friction properties is demonstrated.Institute of Mechanics of Metal—Polymer Systems, Academy of Sciences of the Belorussian SSR, Gomel'. L. Ya.Karpov Scientific-Research Physicochemical Institute, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 839–842, September–October, 1974.     

Temperature - time analogy for thermorheologically complex polymeric materials

Conclusions 1. The viscoelastic properties of mixtures of crystalline polymers with elastomers have been studied as functions of temperature. It is shown that, for mixtures of PP with PIB and TEP, the concept of thermorheologically simple behavior is applicable only within a narrow interval of temperature.2. Parameters of the temperature—time analogy for thermorheologically complex materials have been calculated. It is established that, at temperatures above a characteristic temperature T*, a strong dependence of the correction coefficient on time and a strong dependence of the relaxation function on the ratio of components exist.3. It is shown that use of the concept of thermorheologically complex behavior for prediction of the long-term deformability allows analysis of the contributions of specific components to the viscoelastic behavior of the mixture in different temperature intervals.Paper presented at the Third All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1976.Okhtinsk Scientific-Industrial Association "Plastpolimer," Leningrad. Translated from Mekhanika Polimerov, No. 4, pp. 614–620, July–August, 1977.     

Physical and physicochemical modification of polymers

Research on the modification of the properties of crystalline polymers by changing their physical structure is reviewed. Two different modification principles are considered — the creation of a homogeneous physical structure (introduction of small amount of highly dispersed regulators of the structure-forming processes) and the creation of an inhomogeneous physical structure (by contact with large regulating surfaces) in order to differentiate the surface from the bulk properties and improve resistance to the development of defects. The question of regulation of the processes of physical structure formation by the introduction of chemically reacting substances is also investigated. The possibilities of using antioxidants as physical modifiers and the possibility of physical modification during both the processing and synthesis of polymers are stressed.L. Ya. Karpov Scientific-Research Physicochemical Institute, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 395–408, May–June, 1972.     

A study of the dynamic,mechanical properties of three-dimensional polymers of oligoester acrylates over a wide temperature range

The effect of the chemical structure of three-dimensional polymers of oligoester acrylates on the dynamic, mechanical properties is investigated over a wide temperature range. It is observed that the properties of oligoester acrylates depend on the nature and dimensions of the oligomer block and on the nature of the main chains. The observed relaxational transitions can be explained by the movement of various molecular groups.V. I. Lenin State Pedagogic Institute, Moscow. Institute of Chemical Physics, Academy of Sciences of the USSR. Translated from Mekhanika Polimerov, No. 6, pp. 993–998, November–December, 1972.     

Viscoelastic parameters of certain polymers in the temperature interval 4.2–240°K

The principal elastic constants of Nylon 6, Nylon 7, Nylon 6.10, Nylon 11, Nylon 12, PVC, PMMA, polystyrene, and polyvinylfluoride have been calculated from data on the velocity of ultrasonic longitudinal and shear waves measured at a frequency of 5 MHz on the temperature interval 4.2–240°K. It is shown that at cryogenic temperatures the dynamic moduli of elasticity are, to a considerable extent, determined by the characteristics of the chemical structure of the polymers. It is suggested that the Poisson's ratios of the polymers depend on their free volume.Scientific-Research Institute of Plastics, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 604–609, July–August, 1973.     

The acoustic properties of polymers with an asymmetric potential barrier at liquid-helium temperatures

The pulse-phase compensation method has been used to measure the propagation velocities of longitudinal and shear waves in polyvinyl chloride, polyvinyl fluoride, and polystyrene at frequencies of 1 and 5 MHz on the temperature interval 2.1–240°K. It has been established that as the temperature falls to 2.1°K the speed of ultrasound in these polymers monotonically increases, the dispersion (frequency dependence) of the speed of sound being preserved over the entire temperature interval. Two possible causes of the viscoelastic relaxation observed in the investigated polymers in the region of helium temperatures are considered.Scientific-Research Institute of Plastics, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 749–751, July–August, 1973.     

Thermomechanical properties of spot-bonded nonwoven synthetic-fiber materials

The thermomechanical properties of spot-bonded nonwoven synthetic-fiber materials with a polymer binder have been investigated. The materials are composed of heterogeneous fibers, with low-melting polymers (binder) forming the surface layer. The change of deformation in uniaxial tension was studied from 20 to 150° C (rate of temperature increase 1.5° C/min) as a function of the nature of the fibers and the binder, their relative proportions, and the density and weight of the material. A theoretical explanation of the observed effects is offered.Mekhanika Polimerov, Vol. 4, No. 2, pp. 300–303, 1968