Effect of certain additives and the ambient medium on the static and fatigue strengths of polyamides

The change in the static strength of polycaprolactam during heat treatment has been investigated in relation to the type of additive and the ambient medium, and the change in dynamic strength in relation to the method of introducing the stabilizer. It has been observed that there is a slowdown in the thermal oxidation and loss of strength of polyamides exposed to heat in a medium containing stabilizer vapors and of polycaprolactam heat-treated after being coated with lacquer containing a thermostabilizer.On the basis of the experimental material it is suggested that the loss of strength of polyamides associated with thermal oxidation is due principally not to a reduction in molecular weight or crosslinking but to stress concentrations and microdefects associated with rupture of the molecular chain. An effective method of increasing the dynamic strength of polyamides has been found.Mekhanika Polimerov, Vol. 2, No. 1; pp. 60–66, 1966     

Effect of structural-chemical modification of a polycaprolactam block on the retention of strength during thermo-oxidation

The structure and strength of a block of polycaprolactam (PC) have been investigated in relation to diffusion stabilization and thermo-oxidation. It is shown that structural modification of the surface layers of the PC block with zinc iodide has an important effect on the retention of strength during prolonged thermo-oxidation.Kaunas Polytechnic Institute; Institute of Physicotechnical Problems of Energetics, Academy of Sciences of the Lithuanian SSR, Kaunas. Translated from Mekhanika Polimerov, No. 1, pp. 10–14, January–February, 1970.     

Effect of neutron irradiation on the lifetime of polycaprolactam

On the basis of a study of the temperature-time dependence of polycaprolactam irradiated with thermal neutrons, it has been shown that strength and lifetime and the parameters which determine lifetime vary as functions of the radiation dose.     

Effect of processing conditions on the supramolecular structure and strength properties of polycaprolactam

The formation of supramolecular structures in block polycaprolactam is considered. It is shown that technological factors have a considerable effect on the nature of the supramolecular structure. Two of these factors are the temperature gradient of the polymer melt and the nature of its motion in the cylinder of the injection molding machine up to the moment of injection into the mold. It is shown that the nonuniformity of deformation and the considerable number of defects associated with large supraspherulitic formations lead to a deterioration in the strength and deformation properties of polymers.Mekhanika Polimerov, Vol. 2, No. 5, pp. 659–663, 1966     

Fatigue and fracture of stabilized polycaprolactam

We have investigated the effect of certain antioxidants and structure-forming agents on the mechanism and work of fatigue fracture of polycaprolactam under cyclic loading. We have analyzed the super-molecular structures and fracture surfaces of the most typical stabilized specimens and offer an explanation of the fatigue hardening mechanism in stabilized polycaprolactam.Mekhanika Polimerov, Vol. 3, No. 4, pp. 713–718, 1967     

Relation between molecular orientation characteristics determined from birefringence and acoustic data and the effect of orientation on the strength of polycaprolactam fibers

The mean molecular orientation calculated from birefringence and acoustic data has been investigated in relation to the degree of stretching for polycaprolactam fiber. A correlation has been found between the characteristics calculated by these two independent methods. It is shown that the molecular orientation factor calculated from the speed of sound does not depend on crystallinity if the measurements are made below the glass transition temperature. It is confirmed that the strength of the fiber depends importantly on the degree of orientation of the molecular segments in the amorphous zones.Mekhanika Polimerov, Vol. 3, No. 1, pp. 3–7, 1967     

Effect of supermolecular structures on the self-heating of plastics under cyclic loads

It was established that the intensity of self-heating of polycaprolactam specimens under the influence of cyclic loads depends on their supermolecular structure. The coarser the supermolecular structure and the larger its variation across the specimen cross section, the higher is the increase in the specimen temperature due to self-heating. Changes taking place in the supermolecular structures of polycaprolactam specimens under the influence of cyclic loads were analyzed, and it was shown that the introduction of artificial nuclei of structure formation promotes the ordering of supermolecular structures in polycaprolactam, which produces a substantial reduction in the temperature reached as a result of self-heating due to cyclic loads.Mekhanika Polimerov, Vol. 2, No. 6, pp. 803–807, 1966     

Effect of production technology upon the supramolecular structure of crystalline polymers

The supramolecular structure and some other properties (density, microhardness) of high-density polyethylene and polycaprolactam specimens, molded under various conditions and aged for periods up to five months, have been studied.The change in the nature of the supramolecular structure and properties of the tested materials was determined in relation to molding conditions and aging time. It was found that the properties of these materials are determined by their supramolecular structure.Mekhanika Polimerov, Vol. 1, No. 2, pp. 9–14, 1965     

Effect of gamma radiation on the cracking and mechanical properties of Kapron (polycaprolactam)

The results of a mechano-optical investigation of irradiated oriented polycaprolactam film are discussed. After irradiation comparatively large cracks running at right angles to the orientation axis appear in the film; these are responsible for the reduced tensile strength and deformability of the polymer.Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad; Lenin Tadzhik State University, Dushanbe. Translated from Mekhanika Polimerov, No. 4, pp. 756–758, July–August, 1971.     

Deformation of thin polycaprolactam film in uniaxial tension

The individual stages of deformation of spherulitic specimens of polycaprolactam have been studied by a microscopic method. An empirical relation between the total deformation of the specimen and the deformation of the individual spherulite is obtained.     

Behavior of the supermolecular structure of oriented amorphous-crystalline polymers under cyclic loading

Equipment has been developed for investigating small-angle X-ray diffraction in various phases of the loading period in cyclically extended polymers. The behavior of the large-period structure of oriented polycaprolactam (kapron) films in cyclic extension has been studied. The results are compared with the data on the behavior of the same structure in static tests.Mekhanika Polimerov, Vol. 4, No. 2, pp. 195–199, 1968     

Study of behavior of plastics during production and aging. Polycaprolactam

The effect of molding conditions on the mechanical properties of polycaprolactam (nylon-6) is examined, together with the variation in these properties with time. The experimental data lead to the conclusion that the mechanical properties of polycaprolactam depend on the degree of interaction between two processes: relaxation of the internal residual stresses and the ordering of the structure.Mekhanika polimerov, Vol. 1, No. 1, pp. 17–25, 1965     

Temperature reversal of the reinforcing effect of fillers

A previous investigation [4] of the tear strength of filled systems based on SKS-85 butadiene-styrene copolymer over a broad temperature interval revealed a reversal of the reinforcing effect of fillers with a coefficient of thermal expansion different from that of the filled polymer. At Tg the strength of mixtures containing polymer fillers [Kapron (polycaprolactam) and cellophane powder] exceeds that of mixtures containing chalk and carbon black. The temperature reversal effect is attributed to the severe weakening of the adhesion of the polymer to the surface of the filler particles as a result of the concentration of shrinkage stresses in the polymer-filler contact zone. The presence of shrinkage stresses around the filler particles at Tg is qualitatively demonstrated on model systems using a photoelastic technique. Moreover, it is shown that the unbalance, and hence the residual stresses, in filled systems at temperatures below the glass transition temperature of the filled polymer is determined by the difference in the coefficients of thermal expansion.Moscow Technological Institute of the Meat and Dairy Industry. Translated from Mekhanika Polimerov, No. 4, pp. 579–583, July–August, 1969.     

Fatigue and fracture of plasticized and stabilized polyamides

Polyamides have been tested in cyclic bending to determine the effect of certain plasticizers, plasticizing conditions, diffusion stabilization, and aging on the mechanism and energy of fatigue fracture. The fracture surfaces of the most typical plasticized specimens are analyzed. The optimal conditions of diffusion stabilization of polyamides with quinhydrone, giving a considerable improvement in antifatigue properties, are selected.Institute of the Physicotechnical Problems of Power Engineering, Academy of Sciences of the Lithuanian SSR, Kaunas. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 693–697, July–August, 1968.     

Some specific features of the development of destructive fissures in polymers

The author discusses the specifics of fissure development in polycaprolactam (Kapron). He observed the formation of a frontal prefissure zone in which the material had changed. In the brittle destruction of oriented polycaprolactam and polymethylmethacrylate and at high rates of fissure motion, the motion assumed an autovibratory character.Institute of Mechanics Problems, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 547–550, May–June, 1973.     

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.     

Polyformaldehyde as an antifriction material

The antifriction properties of polyformaldehyde have been studied on the velocity interval from 4 · 10^–4 to 10 m/sec and at loads to 300 kgf/cm². Tests were conducted with and without lubrication on laboratory friction machines of various types and under service conditions. Steel, emery cloth, and polyformaldehyde were used as the second member of the friction pair. The values of the coefficients of friction, temperatures and performance limits for polyformaldehyde are compared with those for polycaprolactam.All-Union Scientific Research Institute of Railroad Transport, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 850–856, September–October, 1969.     

Effect of crystallization on the adhesion of polycaprolactam to metal

The effect of the melt cooling and annealing conditions on the supermolecular structure of polycaprolactam and its adhesion to aluminum has been studied. It is shown that the transition from amorphous-mesomorphous to crystalline structure leads to a decrease in adhesion.Institute of Mechanics of Metal-Polymer Systems, Academy of Sciences of the Belorussian SSR, Gomel'. Translated from Mekhanika Polimerov, No. 1, pp. 170–172, January–February, 1976.     

Effect of the thermal regime on the supermolecular stpuctures and certain ppoperties of polycaprolactam coatings

The effect of the thermal regime on the supermolecular structures and certain physico-mechanical properties of polycaprolactam coatings obtained on heated substrate specimens in a fluidized bed is considered.Division of Polymer Mechanics, Academy of Sciences of the Belorussian SSR, Gomel. L. Ya. Karpov Scientific-Research Physicochemical Institute, Moscow. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 195–200, March–April, 1969.     

Mechanism by which tension on the fibrous filler affects the structure and the strength of wound glass-plastics

Conclusions 1. We have studied how the structure of glass-plastics wound with twisted threads is affected by tension on the fibrous filler. The trend of changes in fiber content and porosity, as well as an increasingly nonuniform distribution of the reinforcing filler over the thickness, has been established.2. The effect of a nonuniform filler distribution over the thickness on the tensile strength has been evaluated. The calculated and the experimental curve of strength as a function of the tension have been compared, the former taking into account variable porosity, fiber content, and nonuniformity of fiber distribution over the thickness.3. It has been demonstrated that the change in the strength characteristics of a wound glass-plastic as a function of the tension on the reinforcing filler during winding is due to a combined complex effect of such factors as the overall fiber content and porosity, a nonuniform fiber distribution over the thickness, the fiber orientation, and the degree of mechanical damage in threads due to their interaction with the active components of the winding machine.Report presented at the Third All-Union Conference on Polymer Mechanics. Riga, November 10–12, 1976.Translated from Mekhanika Polimerov, No. 3, pp. 439–444, May–June, 1977.