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     

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.     

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.     

Causes of the fluctuation of the strength of a block of polycaproamide exposed to the action of heat

Fractography and mechanical testing are employed to investigate the fracture mechanism of polyamide blocks exposed to the action of heat. The mode of fracture depends essentially on the dangerousness of the surface defects.Kaunas Polytechnic Institute; Institute of Physicotechnical Problems of Power Engineering, Academy of Sciences of the Lithunian SSR, Kaunas. Translated from Mekhanika Polimerov, No. 4, pp. 642–645, July–August, 1969.     

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     

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.     

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