Effect of fillers on the structure and properties of cured resins

The elastic (modulus of elasticity and equilibrium high-elastic modulus) and thermal (volume coefficients of thermal expansion below and above the glass transition temperature) properties of compositions based on ÉD-5 epoxy resin cured with polyethylenepolyamine have been investigated. Quartz powder and aluminoborosilicate glass powder were employed as fillers at concentrations from 0 to 0.413. The thermal expansion coefficients of the compositions were studied in a dilatometer, in which the specimen is free of mechanical loads. The Young's modulus at 25°C and the equilibrium high-elastic modulus at 125°C of the compositions were determined in the compression regime in an instrument based on the IZV-2 optical length gage. The thermal expansion coefficients of the polymer matrix were calculated with allowance for the elastic properties of the resin and the filler. It is shown that, as the filler concentration increases, the thermal and elastic properties of the resin in the filled system change. This can be interpreted as a change in the properties of the resin as it approaches the surface of the filler particles. Increased interaction between the filler surface and the epoxy resin tends to stiffen the polymer network.Scientific Research Institute of Precision Technology, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1018–1022, November–December, 1969.     

Effect of an electron beam on the structure of epoxy resins

It is shown that exposing a cured epoxy resin to the action of an electron beam leads to a change in the structure outside the zone of direct action of the beam; this is accompanied by the formation of diffraction rings in the electron diffraction pattern and a change in microhardness.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 523–525, May–June, 1976.     

Effect of water on the adhesion of epoxy resin to steel

The change in the adhesion of epoxy resin to steel in the presence of water has been investigated. It is shown that under these conditions the adhesion is reduced. The reduction is reversible above and irreversible below the glass transition temperature of the resin.Ural Scientific-Research Chemical Institute, Sverdlovsk. Translated from Mekhanika Polimerov, No. 4, pp. 733–736, July–August, 1971.     

Investigation of the adhesion of epoxy resin ED-5 to metals

The strength and thermostability of metals bonded together by epoxy resin ED-5 pass through a maximum with increase in the concentration of curing agent (tetraethylene pentamine). Cohesion type fracture changes to adhesion type at a certain concentration of the hardener. It has been suggested that a change in the character of the polymermetal bond is the cause of the observed dependences.The appearance of breaks or maxima at 80°–120° C on the curves of the temperature dependence of the strength of the glued joints is explained by changes in the physical state of the polymer.Mekhanika Polimerov, Vol. 1, No. 6, pp. 108–113, 1965     

Study of the residual (internal) stresses in reinforced epoxy resin

An optical polarization method has been used to study the residual (internal) stresses in reinforced ED-6 epoxy resin cured with maleic anhydride. The effects of "chemical" shrinkage, volume change relaxation during during curing, and the difference linear coefficients of thermal expansion for reinforcement and resin are elucidated. It is shown that adjacent reinforcing elements interact. The stress state is investigated with reference to a model of the elementary cell of the regular structure of a unidirectional glass-reinforced plastic. The residual stresses are found as a function of the resin/reinforcement ratio.Mekhanika Polimerov, Vol. 1, No. 4, pp. 76–80, 1965     

Effect of boundary-layer processes on the strength of glass-reinforced plastics

It is shown experimentally that the strength of glass-reinforced plastics is determined by the properties of the resin close to the fibers; these depend on the structure and chemical composition of the fiber surface. A study is made of the effect of modification of the glass fiber on curing conditions in the layer next to the fiber for a number of resins (K9 silicone resin, ED-6 epoxy resin, polyacrylate-911, and furfural PF resin).Mekhanika polimerov, Vol. 1, No. 1, pp. 26–35, 1965     

Effect of harmonic shear deformations on the viscosity of epoxy potting compounds

A method has been developed for experimentally determing the effect of harmonic shear deformation on the effective viscosity of pseudoplastic liquids. Harmonic deformation substantially reduces the effective viscosity of a filled composition based on epoxy resin ED-5.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 328–331, March–April, 1969.     

"Freezing" and "defreezing" effects in the photoelastic investigation of temperature stresses

The "freezing" and "defreezing" temperature limits of an optically active material based on an epoxy resin have been experimentally investigated. A method of determining the mean value of the optical coefficient when the material is heated on the "freezing" temperature range is considered. The lower "defreezing" temperature limit has been experimentally established. The results of the investigation are presented in the form of graphs.Translated from Mekhanika Polimerov, No. 3, pp. 501–506, May–June, 1976.     

Mechanism of occurrence of microcirculatory phenomena in a constant magnetic field

A motion-picture study of the capillary network of the interdigital membranes of frogs has been carried out in order to clarify a number of effects observed after individual parts of the body and the whole organism are placed in a constant magnetic field. A constant magnetic field is observed to have three principal effects on the blood flow. The intensified blood flow following exposure to the field is explained as a complex reflex response mechanism, in which a definite part is played by a change in blood particle potentials and by processes of aggregation with subsequent disaggregation.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics on the topic: Problems of Microcirculation and Mass Transfer, Riga, October, 1975.Riga Scientific-Research Institute of Traumatology and Orthopedics. Translated from Mekhanika Polimerov, No. 5, pp. 891–894, September–October, 1975.     

Periodic shear deformation of a curing epoxy composition

The curing of an epoxy resin with amines is investigated in relation to the changes in the viscoelastic shear characteristics. The effect of the shear deformation amplitude on the curing kinetics is considered.Presented at the Symposium on Polymer Rheology, Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow, May, 1970.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 301–306, March–April, 1971.     

The Effect of an Active Diluent on the Properties of Epoxy Resin and Unidirectional Carbon-Fiber-Reinforced Plastics

The influence of an active diluent on the properties of an epoxy matrix and carbon-fiber-reinforced plastics (CFRP) is investigated. The physicomechanical properties of an ED-20 epoxy resin modified with diglycidyl ether of diethylene glycol (DEG-1), the adhesion strength at the epoxy matrix–steel wire interface, and the mechanical properties of unidirectional CFRP are determined. The concentration of DEG-1 was varied from 0 to 50 wt.%. The properties of the matrix, the interface, and the composites are compared. It is stated that the matrix strength affects the strength of unidirectional CFRP in bending and not their strength in tension, compression, and shear. The latter fact seems somewhat unexpected. The interlaminar fracture toughness of the composites investigated correlates with the ultimate elongation of the binder. A comparison between the concentration dependences of adhesion strength and the strength of CFRP shows that the matrices utilized provide such a high interfacial strength that the strength of CFRP no longer depends on the adhesion of its constituents.     

Viscoelasticity of a curing epoxy composition in the "critical branching" region

The curing of an epoxy resin in the "critical branching" region has been investigated by mechanical and infrared spectroscopy. It is shown that the effective molecular weight between network points (M_c) during the polymerization of an actual system can be determined from the relaxation spectrum in the curing stage investigated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 154–158, January–February, 1976.     

Statistical characteristics of the mechanical properties of glass-reinforced plastics

A statistical analysis has been made of experimental data on the mechanical properties of a glass-reinforced plastic based on T₁ glass fabric (Soviet standard GOST 8481-61) and IF-ÉD-6 epoxy resin (Elektroizolit Plant, tech. spec. TU 26-59) obtained by testing specimens cut from the waste of wound cylindrical shells. The data obtained can be used for estimating the mechanical reliability of products composed of glass-reinforced plastics of this type.Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 131–134, January–February, 1971.     

Shrinkage of epoxy cements during hardening

The authors give the results of measurements of the densities of two types of epoxy resin binders during setting from the initial liquid to the final state at room temperature. They assess the role of thermal shrinkage in the overall shrinkage deformation. They show that the coefficient of shrinkage relative to the state of lowest density is greater than the values given in the literature.Moscow Power Institute. Translated from Mekhanika Polimerov, No. 1, pp. 178–181, January–February, 1972.     

Changes in the structure of polymeric materials in a magnetic field

It is shown that the action of a magnetic field leads to a change in the supermolecular structure of crystalline polymers. The creation of an oriented state in amorphous thermoplastics and thermosets is accompanied by an increase in their hardness and the homogeneity of the structural state.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 737–739, July–August, 1973.     

Determination of the magnitude and distribution of the initial stresses in glass-reinforced plastics

The stresses that develop in the resin at and near the glass-resin interface during the curing of polyester and epoxy glass-reinforced plastics have been experimentally studied by the photoelastic method. The volume state of stress in three mutually perpendicular directions in various sections and in the danger zones is qualitatively and quantiatively described. It is established that the stresses investigated may be the cause of cracking that reduces the tightness and strength of the glass-reinforced plastic.I. M. Gubkin Moscow Institute of the Petrochemical and Gas Industry. Translated from Mekhanika Polimerov, No. 4, pp. 661–667, July–August, 1973.     

Magnetic Catalysis of the P-Parity-Breaking Phase Transition of the First Order and High-Temperature Superconductivity

In the framework of a (2+1)-dimensional P-even gauge theory based on the massive Gross–Neveu model, we show that an external magnetic field induces the P-parity-breaking phase transition of the first order. A dynamical generation of the Chern–Simons term and fractional particle spin and statistics occurs at the critical point. The results in the paper can be interesting in connection with recently discovered phase transitions in high-temperature superconductors.     

Creep simulation in polymer matrix — disperse filler composites

The deformation properties of composites with disperse fillers in close to maximum amounts were investigated. Two types of matrices were selected: epoxy resin with high structural stability in filling, and a crystalline polymer-trioxane-dioxolane copolymer. Materials with a high and low relative surface area-diatomite and ceramic-were used as fillers. The elastic properties were simulated with the Kerner model and creep was simulated with its viscoelastic analog. The model was extended to a matrix-filler-buffer layer model. The possibility of estimating the part of the matrix entering the pores of the filler was examined. Differences in the use of the structural models in predicting elasticity and viscoelasticity were examined. The best results in describing creep were obtained for epoxy resin-ceramic filler composites which have the least interaction between matrix and filler. The possibility of estimating the change in the degree of crystallinity of the matrix and formation of buffer layers in filling with active fillers was examined.Presented at the Ninth International Conference on the Mechanics of Composite Materials (Riga, October, 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 6, pp. 754–768, November–December, 1995.     

Lifetime of amorphous polymers under intermittent loading

The lifetimes of two types of amorphous polymers (polyvinyl chloride and plasticized epoxy resin) under intermittent loading have been investigated. It is established that the lifetime, determined without allowance for recovery time, is less than that under constant load. Under periodic loading at constant stress the lifetime varies with the loading regime. For each of the investigated polymers a lifetime minimum is observed at a certain duration of the loading and recovery periods.Higher Chemical Technology Institute, Sofia. Translated from Mikhanika Polimerov, No. 5, pp. 912–916, September–October, 1971.     

The scale effect and the statistical theory of strength of polymer coatings

As a result of normal tensile tests on coatings based on ED-6 epoxy resin and kapron applied to a metal surface it has been established that the fracture is brittle in character and accompanied by a scale effect and a regular distribution of the strength values for specimens of the same type. It is shown that the data obtained are all in good agreement with the statistical theory of strength.State All-Union Scientific-Research Technological Institute for the Repair and Maintenance of Tractors and Agricultural Machinery, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 839–843, September–October, 1968.