Effect of heat treatment on the strength and supermolecular structure of oriented polycaproamide

The mechanical properties of stabilized polycaproamide have been studied in relation to changes in supermolecular structure, preliminary orientation and duration of heat treatment. The deformation of the spherulites during the orientation of stabilized polycaproamide has been investigated together with the changes in supermolecular structure in the course of heat treatment. Certain relations between strength, type of deformation, and degree of preliminary orientation have been obtained for stabilized and heat-treated polycaproamide. The cause of the formation of inhomogeneous structural elements during polyamide processing are discussed.Mekhanika Polimerov, Vol. 4, No. 3, pp. 402–405, 1968     

Effect of fillers on the hardness and structural order of polymers

The effect of various finely dispersed filler particles differing in size, structure, and the chemical nature of the surface, on the hardness of one crystalline (polycaproamide) and two amorphous (polystyrene and polymethylmethacrylate) polymers has been experimentally investigated. The observed changes in hardness are related with a change in the structural order of the polymer under the influence of the filler and with the formation of structures of different strength by the fillers in the polymer.Kiev Shevchenko State University. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1077–1081, November–December, 1968.     

The effect of stabilizers on the fatigue strength of polycaproamide under tension - compression

The authors give the results of an investigation of the influence of various stabilizers (quin-hydrone, iodine, potassium iodide, DNPDA, and MoS₂) on the fatigue strength and endurance of polycaproamide (PCA) under cyclic compression/tension, both with _a = const and with _a = const. The effectiveness of the stabilizers is mainly governed by the structural changes in the polymer during the stabilization process.Kaunas Polytechnic Institute. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 562–564, May–June, 1973.     

Dependence of the properties of polycaproamide obtained in the presence of benzhydrazide on the symmetry type of the unit cell

The structure and properties of polycaproamide obtained in the presence of benzhydrazide have been studied. They are shown to depend on the duration of application of pressure in the mold. Under tensile deformation a transition from hexagonal to monoclinic polycaproamide takes place in the neck.Lugansk Machine-Building Institute. Institute of the Chemistry of High-Molecular Compounds, As UkrSSR, Kiev. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1125–1127, November–December, 1968.     

Effect of the cellular structure on thermal conductivity of rigid closed-cell foam polymers during long-term aging

The thermal conductivity of rigid closed-cell polyurethane foams during long-term aging has been studied. The similarity between the kinetics of changes in the physical and mechanical characteristics of PU foams on progressive aging is established, which is attributed to the effect of matrix destruction. It is found that rigid foams have cell walls of various strength, whose impact on the kinetics of changes in the physical characteristics of the foams during long-term aging is ascertained. The results of predicting the thermal conductivity of PU foams by the method of temperature-time analogy and establishing the limits of its application are discussed. The research presented is of interest both in determining the foam durability and in replacing freons by alternative, ecologically less harmful blowing agents.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 187–198, March–April, 1999.     

Effect of electrical discharges on the mechanical strength and molecular weight of polystyrene film

Electrically aged polystyrene film was examined to determine the effect of voltage, aging time, and nature of the medium on the mechanical strength and molecular weight. It was established that the changes in the mechanical strength and molecular weight of the film always correspond.Mekhanika Polimerov, Vol. 4, No. 1, pp. 59–63, 1968     

Change of strength of polymeric materials in the process of orientation

In the process of orientation the strength of polymeric materials changes as a result of a net increase in the number of ordered structural elements. It is shown that the model obtained can be used to predict the effect of orientation on the strength of polymers. The theoretical relations satisfactorily describe the available experimental data.Scientific-Research Institute of the Tire Industry, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 848–853, September–October, 1970.     

Effect of aging of the binder on the creep of polymer concrete

Two polyester concretes with diabase and marble fillers and aggregates are used as examples to illustrate the possibility of using a structural approach to evaluate the creep of the composite in the initial state and after preliminary aging under laboratory conditions for a period of 12–13 yrs. Experimental study of the creep of polymer concrete and its structural components (resin and binder) after preliminary aging at elevated temperatures (60, 90°) established that the change that occurs in viscoelastic compliance with aging conforms to the analogy principle with a reduction function that depends on aging temperature and time.Institute of Polymer Mechanics. Latvian Academy of Sciences Riga, Latvia. Central Laboratory of Physico-chemical Mechanics Sofia. Bulgaria. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 6, pp. 787–794, November–December, 1996.     

Structural changes and defect development in epoxy adhesive compounds during thermal aging

The structural characteristics of epoxy adhesive compounds and the development of surface defects during thermal aging have been investigated. Profilograms of the fracture surfaces of bonded joints have been obtained and certain causes of the increased dispersion of the bond strength characteristics explored.Mekhanika Polimerov, Vol. 4, No. 2, pp. 293–295, 1968     

Variation of certain mechanical properties of human compact bone tissue with age

The nature of the variation of the moduli of elasticity, shear moduli, and flexural and torsional decrements of human compact bone tissue during biological aging has been investigated. It has been found that the moduli of elasticity and shear moduli increase sharply up to age 20–25 and then progressively fall; the distribution of the modulus of elasticity over the individual zones of the cross section of the tibia changes significantly with age. By investigating the changes in the logarithmic decrements by nondestructive methods it is possible to estimate the changes in the mechanical and structural properties of the bone.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 885–891, September–October, 1974.     

Effect of uniaxial tension on the density distribution in polycaproamide

The effect of uniaxial tension on the density of polycaproamide has been studied in the temperature region from +20 to +150°C. The density measurements were made by the flotation method. It is shown that the relative change of density increases with temperature. An empirical formula for the density distribution along the stretched specimen is proposed.Severodonetsk Glass-Reinforced Plastics Plant. Lugansk Mechanical Engineering Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 760–761, July–August, 1968.     

Strengthening of Polypropylene Strips by Orientational Stretching in Liquids

Data on the orientational stretching of polypropylene strips in process liquids serving as plasticizers of polypropylene are presented. Such a stretching allows one to avoid many complications characteristic of stretching in air and to increase the maximum stretch ratio significantly (up to 15). The stretching of strips is accompanied by changes in the crystalline structure of polypropylene and by transformation of the amorphous phase into a crystalline one. It is established that the specific strength of the orientationally stretched strips as a function of stretch ratio has a maximum. This is caused by the competing processes of macromolecule orientation in the stretching direction and the destruction of molecular bonds, which leads to the origination of microdamages in the strip surface layer and to a growing content of amorphous phase. It is shown that the extraction of process liquids from the stretched strips increases their specific strength by 20–30%.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 251–264, March–April, 2005.     

Prediction of changes in the strength of filled thermoplastics upon aging in an oxidizing atmosphere

Problems related to analyzing specimens with damaged surface layers have been examined using polyamide, trioxane—dioxolane copolymer, and polycarbonate as source materials. A model was developed for the brittle fracture of block specimens with damaged surface layers, which provides an estimate of the restraints to plastic deformation in these layers. Three segments are seen in the strength—time curves featuring 1) increasing strength, 2) decreased strength with brittle fracture, and 3) constant low strength. The strength of filled specimens of a specific period permits us to evaluate the effect of the filler on the fracture resistance of the matrix. A method was proposed for predicting the strength of filled samples using the matrix aging data.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 3, pp. 375–380, May–June, 1993.     

Concerning the strength and fracture of thermally aged polycarbonate

The change in the strength, fractography, and supermolecular structure of polycarbonate after thermal aging has been experimentally investigated. It is shown that the fall in the strength of the polycarbonate after aging (T 160°C) is chiefly related with the formation of dangerous defects as a result of the destruction of the supermolecular structure at the surface of the block. It is noted that under the same conditions there is some ordering of the supermolecular structure of the polycarbonate at depths of 150 µ or more, but this has practically no effect on the strength characteristics.Institute of Physicotechnical Problems of Energetics, Academy of Sciences of the Lithuanian SSR, Kaunas. Translated from Mekhanika Polimerov, No. 5, pp. 951–952, September–October, 1971.     

Comparison of the temperature-time dependences of polymer strength under static and cyclic loading

A comparison of the temperature-time dependences of the strength of highly oriented fibers under static and cyclic loading shows that in the region of high temperatures and low loading frequencies the static and cyclic specimen lives always coincide. The discrepancy between the static and cyclic lives observed in the region of low temperatures and higher loading frequencies is related with differences in the structural changes in the different loading regimes. These changes are relaxational in nature.The experimental data were reported at the 14th and 16th All-Union Conferences on High-Molecular Compounds (1964 and 1966).A. F. Ioffe Physicotechnical Institute, Leningrad. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 648–655, July–August, 1968.     

Durability of polymers as a function of loading regime during repeated loading with a small number of cycles

Specimens of oriented polycaproamide and unoriented polymethyl methacrylate subjected to uniaxial extension were used to study durability as a function of the number of loading cycles and the intervals between them in different segments of the creep curve. It was shown that the deformation hardening during the initial segment of the creep curve governs the ability of the specimen to withstand subsequent loading cycles. With a relatively low loading rate, deloading-loading cycles during the initial segment of the creep curve lead primarily to an increase in local stresses. During the second stage, repeated loading causes principally an increase in local heating. The interval between loading cycles has only a weak influence on durability.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 252–256, March–April, 1972.     

Results from investigations into the antifrictional characteristics of a group of polymer compositions based on epoxide resins

The results are presented from comparative investigations into the antifrictional and mechanical properties of polymer compositions based on epoxide resins ÉD-5, ÉD-6, and fillers in the form of finely dispersed powders of polymeric materials [polyfluoroethylene, polycaproamide (Kapron B), polyethylene, graphite, sawdust], Babbitt metal B-83, and solidol US-2 grease. The investigations show that the above-mentioned materials are not inferior in their antifrictional characteristics to the widely used nonferrous metals (Babbitt B-83, TsAM 9-1.5, bronze OTsS 5-5-5). The rational regions of use of the investigated compositions are indicated.Rostov-on-Don Institute of Railroad Engineers. Translated from Mekhanika Polimerov, No. 1, pp. 87–90, January–February, 1972.     

Effect of UV radiation and vacuum on the strength and failure of polymer films

The effect of UV radiation and vacuum on the strength and failure of polytetrafluorethylene (PTFE) films has been studied. After irradiation samples were extended in air. It was found that the strength and plasticity of the films is diminished by irradiation in vacuum or in air.Mekhanika Polimerov, Vol. 2, No. 3, pp. 359–364, 1966     

Statistical laws of fracture and statistical estimation of the static strength of structural elements made from polymeric composites

The basis of the statistical estimation of the strength of structural elements made from fibrous composites is considered; the statistical characteristics of the strength of these materials are described and the limit states are formulated. Special attention is given to the resistance to debonding. The conditions of fracture of this class of materials in plane stress are subjected to a statistical analysis.Presented at the 2nd All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1971.Aviation Engineering Institute, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 466–482, May–June, 1972.     

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.