Scanning electron microscope study of the structure of carbonized polyacrylonitrile fibers

The morphology and physicomechanical properties of carbonized PAN fibers (oxidized and heat-treated to 1500, 2000, and 2750°C) have been studied. It is shown that surface and internal structural defects sharply reduce the values of the physicomechanical characteristics of the carbonized fibers. The scanning electron microscope reveals the nonuniformities of the fiber over the fracture surface and makes it possible to take into account the effect of macro- and microdefects in studying fiber strength.Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Institute of Fossil Fuels, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1122–1124, November–December, 1971.     

Effect of temperature on the mechanical properties of boron fibers

The effect of exposure to temperatures on the interval 20–600°C for up to 1000 h on the physicomechanical properties of boron fibers at room temperature has been investigated. Prolonged exposure to temperatures up to 200°C does not have much effect on the mechanical characteristics of the fibers, whereas heating for one hour at 300–350°C increases the strength of the fibers by 10–12%.All-Union Scientific Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 329–332, March–April, 1971.     

Modification of glass-filled polyamide 66 by reactive oligoorganosilane

Properties of glass-filled polyamide 66 modified by reactive oligoorganosilane were investigated. It was found that modification led to the improvement of the rheological properties of polyamide. The addition of the modifier decreased the glass transition temperature T_g of the polyamide from 60 to 50–59°C, without affecting the melting point. Composites modified by oligoorganosilane are characterized by higher (10–40°C) temperatures of onset and 50% weight loss as compared to the initial composite. It was found that chemical reaction of oligoorganosilane with polyamide and glass fibers took place during coextrusion of the modifier and polyamide, which formed firm chemical bonds between the polyamide and filler and thus favored a considerable improvement in the physicomechanical properties of the composite. The change in the structure and properties of the polyamide observed during modification by oligoorganosilane significantly affected its behavior during friction. The modification made it possible to increase the wear resistance of the composite 1.5 to 2 times and to decrease its friction coefficient from 0.38 to 0.27–0.33. It was also found that the ability of oligoorganosilane to react during its processing with water in the polyamide allowed for a significant decrease in the intensity of hydrolytic processes in the polymer. Because of this, the physicomechanical, rheological, and antifrictional properties of modified composites with an increased content of moisture (up to 3%) in the initial polyamide surpass similar characteristics of the composites containing no modifier, with not only enhanced but also optimum (0.2%) humidity of polymer granules.Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 4, pp. 545–553, July–August, 1998.     

Effect of the conditions of bond formation and destruction on the adhesion of polymers to synthetic fibers

It is shown that the adhesion of linear polymers can be measured by shearing a monofilament relative to a microblock of adhesive [1]. Experiments have been performed on polypropylene, polyethylene terephthaliate, polycaprolactam, polyvinyl alcohol, and glass fibers. Broad variation of the diameter, structure, and physicomechanical properties of the various kinds of oriented fibers had practically no effect on the adhesion. The physicochemical properties of the adhesive solutions at the moment of application to the fiber likewise do not affect the adhesion which, other things being equal, is determined by the nature and supermolecular structure of the polymers in the contact zone.Belorussian Lenin State University, Minsk. Branch of the Karpov Scientific-Research Physicochemical Institute, Obninsk. Translated from Mekhanika Polimerov, No. 6, pp. 1042–1048, November–December, 1970.     

Structural residual stresses in oriented glass-reinforced plastics

A previously proposed method is used to obtain expressions for calculating the residual stresses as a function of the physicomechanical properties of the polymer matrix and the reinforcement ratio. The calculation results are presented and the corresponding state of stress and strain analyzed. There are considerable deviations (in the magnitude and distribution of the stresses) from models that neglect or only take partly into account the interaction of the fibers.Moscow Ordzhonikidze Aviation Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1051–1058, November–December, 1968.     

Statistical characteristics of the mechanical constants of glass-reinforced plastics

The results of statistical treatment of experimental data on the physicomechanical properties of glass-reinforced plastics, based on alkali-free, aluminoborosilicate glass fibers (composition NS-55/6) with paraffin as lubricant and epoxyphenolbutyral composition EFB-4, obtained from tensile tests on flat specimens prepared by "wet" winding on a mandrel, are given. The data can be used for evaluating the effect of the scatter of the mechanical constants of a composite material on the efficiency of a structure and its elements.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 6, pp. 1125–1128, November–December, 1972.     

Glass-reinforced plastics based on matrices combining thermoplastics and thermosetting plastics

The conditions of fabrication and the physicomechanical properties of glass-reinforced plastics based on polysulfone combined in different ratios with epoxy resin and Rolivsan were investigated. It was found that realization of the strength of the fibers in glass-reinforced plastics based on three types of binders and mixtures of them at room temperature is approximately the same. The lower strength of glass-reinforced plastics based on polysulfone is determined by the lower concentration of fibers. Modification of thermosetting plastics with polysulfone significantly increases (by 5–8 times) the specific energy of delamination of the glass-reinforced plastics G_1c, which should be manifested by an increase in their crack resistance and other operating characteristics. Modification of ED-20 with polysulfone and polysulfone with Rolivsan significantly increases the glass transition temperature of the polymer and affects the character of the temperature curves of the strength of the glass-reinforced plastics.Institute of Chemical Physics, Russian Academy of Sciences, Moscow. D. I. Mendeleev Russian Chemical Technological University, Moscow. Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 111–117, January–February, 1996.     

Effect of the molecular weight of the polystyrene matrix on the physicomechanical properties of impact polystyrene

The effect of the molecular weight of the polystyrene on the properties of impact polystyrene obtained by mechanical mixing of polystyrene and rubber has been investigated. As the molecular weight of the polystyrene increases, the physicomechanical properties of the impact polystyrene improve and its rheological properties deteriorate. There is a definite correlation between the physicomechanical properties of the polystyrene and those of the impact polystyrene.Scientific-Research Institute of Synthetic Rubber, Kralupy-on-Vltava, Czechoslovakia. Translated from Mekhanika Polimerov, No. 3, pp. 545–546, May–June, 1971.     

Change in the properties of impact polystyrene during multiple processing

It has been shown experimentally that the multiple extrusion of grade UP-1E impact polystyrene (5–7 cycles) has almost no effect on most of the physicomechanical properties, the content of volatiles and helium or the residual monomer content. Multiple processing of the same polystyrene by injection molding (10 cycles) causes partial degradation of the material and the destruction of its crosslinked fraction, which results in increased fluidity, reduced molecular weight, and a partial improvement in mechanical properties (approximately up to the fifth or sixth cycle).Mekhanika Polimerov, Vol. 3, No. 1, pp. 156–160, 1967     

Critical length and distribution of fibrous fillers and composites

The adhesion of UKN-01 carbon fibers to a PA-12 polymeric matrix is investigated by the method of testing single-fiber model composites. The distribution of critical fiber length is constructed from measurements of fragment lengths formed in the final stage of testing. Variation in the distribution of critical length is established as a result of surface treatment of the reinforcing fiber. A bimodal distribution corresponds to the initial carbon fiber, and a monomodal distribution to the treated fiber. This is explained by replacement of a physicomechanical type of interaction of the phase interface by a physicochemical interaction owing to electrochemical treatment of the fiber surface. Analysis of the results indicated that each type of interphase interaction has its own characteristic critical length. The selection of critical length has been confirmed for calculation of the interphase shear strength by the Kelly-Tyson formula.Uvikom, Moscow Oblast, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 1, 98–103, January–February, 1997.     

Physicomechanical characteristics of a disperse-filled polytetrafluoroethylene

Composite polymer materials based on PTFE containing ultradisperse -sialon (1–10 wt.%) as the cross-linking agent are studied. It is shown that the injection of small amounts of fillers (1–2 wt.%) increases the degree of composite crystallinity. A correlation between the structure, element distribution on the surface layers of samples, and tribotechnical characteristics of composites is found. The change in the physicomechanical characteristics is associated with the effect of the interstructural plasticization.Ammosov Yakutsk State University, Yakutsk, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 6, pp. 797–806, November–December, 1999.     

Physicomechanical properties of composites from recycled polyethylene and linen yarn production wastes

The possibilities of utilizing wastes of linen thread production (chaffs, spinning and roving losses) in recycled polyolefin composites have been investigated. The wastes were mixed with recycled polyethylenes (produced from domestic and industrial film production wastes). The physicomechanical properties (tensile strength, bending and tensile moduli, and water resistance) and the fluidity (melt flow-behavior index) for systems with a different filler content are estimated. Almost all the composite materials obtained have satisfactory fluidity (melt flow-behavior index is not lower than 0.07–0.15 dg/min). For all types of the composites, a slight increase in tensile strength and a considerable increase (3–7 times) in bending and tensile moduli were observed. The water resistance of the composites decreased with an increase in the filler content. The modification of filled systems with diisocyanates (diphenylmethane diisocyanate) improved the useful properties and water resistance of all the composites investigated.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 199–210, March–April, 1999.     

Effect of the nature of the filler surface on the properties of phenol-formaldehyde molding powders

The physicomechanical properties and microstructure of phenolic molding powders containing fillers with different surface energies have been investigated. It has been found that an increase in filler surface energy leads to an increase in the density of the resin around the filler particles and hence to an improvement in the physicomechanical properties of the molding powder. A parallel investigation of a molding powder containing a lubricant shows that adsorption of the lubricant on the filler surface reduces the density of the resin, which is accompanied by a deterioration in the properties of the material.Scientific-Research Institute of Precision Engineering Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 677–681, July–August, 1968.     

Effect of nature of metallic subs trate on adhesion strength of polyvinylbutyral - metal joints

The effect of the physicomechanical properties of the substrates on the adhesion strength of the metal—polymer system was investigated.Institute of the Mechanics of Polymers, Academy of Sciences of the Latvian SSR, Riga. Institute of Chemistry and Chemical Technology, Academy of Sciences of the Lithuanian SSR, Vil'nyus. Translated from Mekhanika Polimerov, No. 1, pp. 81–86, January–February, 1972.     

Development of forced high-elastic deformations in polystyrene and its self-unloading capacity

The thermodynamic states of two systems of impact polystyrene based on polybutadiene-styrene rubbers are investigated, without introducing spectrography, in terms of the theory of linear viscoelasticity. The results are confirmed by the considerable difference in physicomechanical properties.Ukrainian Scientific-Research Institute of Plastics, Donetsk. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 595–597, July–August, 1968.     

Effect of the composition and concentration of fibrous wastes from linen yarn production on the physicomechanical properties of polyolefin composites

An analysis is made of the feasibility of using wastes from the production of linen yarm (scutch, spinning and carding refuse) to modify low-density polyethylene. The effect of the composition and concentration of wastes on the processing properties (melt index), physicomechanical indices (tensile strength, elastic modulus in bending), and water resistance of composites based on low-density polyethylene is studied. It is found that the melt index decreases with an increase in the content of filler and that even a composite with a high filler content (40–50% by weight) maintains values of 0.2–0.3 g/10 min. The elastic modulus in bending increases with an increase in the content of waste, regardless of the nature of the latter. Tensile strength increases slightly and depends on the choice of filler. This result, combined with the reducation in the scatter of values of elastic modulus with an increase in filler concentration, is an indicator of the relatively high degree of heterogeneity of the systems that were studied. The water resistance of the composites decreases with an increase in filleer content. To reduce the heterogeneity of the systems, mixing should be intensified and modifiers such as stearic acid and polyisocyanates should be added.Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 3, pp. 408–416, May–June, 1997.     

Effect of side branches on the properties of cross-linked polyurethanes

Two series of samples of cross-linked polyurethanes: based on diethylene glycol and polypropylene glycol having calculated M_c 1000, were investigated. In synthesis by partial substitution of glycols by fatty acid ester and triethanolamine, long side branches were created in the structure of the polymer. The effect of the mass concentration of these branches on the physicomechanical properties of polyurethanes was evaluated. The different character of the effect of these branches on the properties of two types of polyurethane was demonstrated.Submitted to the Xth International Conference on Mechanics of Composite Materials (Riga, April 20–23, 1998).Latvian State Institute of Wood Chemistry. Riga, LV-1006 Latvia. Translated from Mekhanika Kompozitnykh Materialov, No. 6, pp. 840–844. November–December. 1997.     

Buildup of defects in polymethyl methacrylate in service and their effect on its notch sensitivity

This study deals with the effect which defects built up in polymethyl methacrylate during 0–16,000 h of service have on its physicomechanical properties, fracture topography, and notch sensitivity. The trend of strength and plasticity characteristics is established as well as that of the coefficients of notch sensitivity as functions of the notch depth.Lenin Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 2, pp. 256–262, March–April, 1976.     

Physicomechanical properties of polyamides with chopped-strand reinforcement

The physicomechanical properties of AS-30 and KS-30 glass-reinforced polyamides have been determined at normal and elevated temperatures under various kinds of short-time and long-time loading.Riga Polytechnic Institute, All-Union Scientific-Research Institute of Glass-Reinforced Plastics and Fiberglass, Moscow Region. Translated from Mekhanika Polimerov, No. 3, pp. 411–415, May–June, 1971.     

Effect of the substrate on the strength of adhesive-bonded joints

The possibility of the adhesion failure of adhesives is discussed. It is shown that the properties of the adhesive film depend on the physicomechanical characteristics of the substrate as a result of the action of molecular forces.V. I. Lenin All-Union Electrotechnical Institute. Translated from Mekhanika Polimerov, No. 2, pp. 295–300, March–April, 1972.