Effect of polymer molecular weight on its reaction with nonporous and porous fillers

The effect of polymer molecular weight (using polyethylene and polyisobutylene) on the formation of polymer contact with the surface of porous and nonporous fillers has been studied. It has been shown that the extent of coating of a nonporous surface by polymer does not depend on polymer molecular weight, but the extent of coating of a porous surface is larger, the lower the molecular weight of the polymer; this is explained by a selective adsorption of macromolecules of lower molecular weight on the porous filler from the polymer melt.     

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.     

Fractial parameterization of the structure of filled polymers

It is suggested to consider the structure of a filled polymer as a set of two or more multifractals. It is shown experimentally that the basic factor determining the fractal dimension of distribution of a disperse filler in the polymer is the size distribution of filler particles.Moscow State Open University, Moscow, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 3, pp 269–290, 1999.     

Experimental study of the contribution of interfacial friction to the deformation resistance of particle-reinforced polymers

A study has been made of the dissipative properties of heavily filled elastomers as influenced by friction of the elastic matrix on the surface of the solid filler particles. In order to model the frictional surface, specimens were predamaged by cyclic deformation, with strain amplitudes sufficient to cause separation of the matrix from the filler. The predeformation operation was performed by means of a mechanical system having individual particle-matrix bonds, so that it was possible to evaluate the contribution of interfacial friction to the resistance of the polymer. When external pressure was applied to the specimens, the width of the hysteresis loop increased with increasing pressure, obviously reflecting an increase of the surface friction in the matrix. It was established that for a given volumetric fill, the dissipation of mechanical energy increased with decreasing particle size (with increasing frictional surface area). The significant influence of interfacial friction on the level and rate of strain relaxation was demonstrated experimentally.Paper presented at the 9th International Conference on the Mechanics of Composite Materials (Riga, October 1995).Translated from Mekhanika Kompositnykh Materialov, Vol. 31, No. 5, pp. 579–583, September–October, 1995.     

Effect of fillers on the viscosity and viscoelasticity of low-density polyethylene melts. Communication 1

An investigation of low-density polyethylenes filled with up to 30% by volume dispersed particles, has shown that for both the matrix and the composites the apparent viscous flow activation energy does not depend on the shear stresses and increases starting from a certain filler concentration at which the conformation range in the matrix is depleted. The dependence of the relative viscosity of the compositions on the volume filler content is satisfactorily described by an equation that contains the reduced filler concentration, defined as the ratio of the nominal filler concentration to the limiting concentration at which the adsorption layers on the particles extend throughout the matrix. The thickness of the polymer layer adsorbed on the particles must be determined from the specific exterior particle surface, with allowance for the volume of the polymer in the sorption space of the porous filler.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 478–486, May–June, 1976.     

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 fillers and solvents on the properties of polystyrene coatings

The mechanism of coating formation from solutions of atactic polystyrene in xylene and carbon tetrachloride has been investigated. It has been established that, as the filler content increases, in coatings formed from polystyrene solutions containing an evaporating solvent the growth of the internal stresses and the thermophysical characteristics is characterized by similarity of slope, as distinct from the case of coatings obtained from systems containing a polymerizing solvent. It is shown that the nature of the solvent has an important effect on the character of the interaction at the polymer—filler interface and on the structure and properties of the coatings.Kucherenko Central Scientific-Research Institute of Structural Design. Institute of Physical Chemistry, AS USSR, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1127–1129, November–December, 1968.     

Physico-mechanical properties of polymer materials and the friction problem

Aspects of the friction behavior of polymer materials associated with their molecular structure and responsible for the relatively small value of the modulus of elasticity as compared with the ultimate strength are examined. It is shown that, in view of the important influence of hydrostatic pressure on the mechanical properties of polymer materials, the mechanical characteristics obtained from uniaxial testing cannot be used in calculating the contact area and the forces of friction. Formulas are presented for calculating the mechanical characteristics under these conditions. The results of indentation experiments designed to simulate contact processes are discussed. It is shown that the resistance to deformation of the asperities on the surface of polymer materials is of the order of the yield stress, and not two or three times greater, as with metals. The results of contact creep studies are described and evaluated. The results of investigations of the mechanical and antifriction properties of filled polymer materials show that the forces of friction are inversely proportional to the modulus of elasticity, while the thermophysical characteristics are a function not only of the thermophysical characteristics of the filler and the base, but also depend to a great extent on the shape of the filler particles; thus, when a fibrous filler with a low coefficient of linear expansion is used, the thermal stability of the friction material can be considerably improved. The results of a study of the adhesion interaction of polymer materials under conditions of omnidirectional nonuniform compression and simultaneous deformation are presented. It is shown that the adhesion interaction is strong even at room temperature. Aspects of the mechanical properties of lubricants that determine their effectiveness in polymer friction are considered.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 303–314, March–April, 1969.     

Plane stress finite element analysis of filler reinforced polymers

The characteristics of polymers such as force-deformation behaviour, strength, fatigue and wear resistance, can be tailored by embedding it with filler particles. The influence of the fillers on the material behaviour significantly depends on the size and geometric form of the filler aggregates, which vary under mechanical loading. The concept of super element is used to model filler particles. This is now coupled with the polymer matrix to generate a finite element model of filler reinforced polymers. In this work, we investigate the effect of filler geometry and volume fraction of fillers on the overall stiffness of the filler reinforced polymer. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of the structure of a polymer matrix and its area of contact with the surface of the filler on the rigidity of a polyethylene composite

The distribution of the orientation of the macromolecules over the wall cross section of a filled polyethylene tube is analyzed. A direct proportionality is established between the degree of orientation (estimated from the shrinkage) and the elastic modulus. The effect of various fillers on the melting and crystallization of low-density polyethylene is considered. For a specified filler concentration the elastic modulus of the composites depends very considerably on the relative area of contact between the polymer matrix and the surface of the filler.Institute of the Mechanics of Polymers, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 387–391, May–June, 1974.     

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.     

Numerical modeling of deformation and fracture of a multiphase polymer concrete

A numerical method for predicting the deformational and strength characteristics of a calcite-quartzitic polymer concrete from the known properties of its components is developed based on the finite-element method. Components of the material are assumed elastic and isotropic, and the filler particles are modeled by round inclusions perfectly bonded to the polymer matrix. The size distribution of the inclusions correspond to that of actual fillers. The destruction process of the components is simulated by sequentially excluding the particles in which the maximum principal stress has achieved the ultimate value for this component. A comparison of calculated and experimental characteristics of the polymer concrete showed errors of 2–4% for the elastic modulus and about 10% for the ultimate strength if the finite-element cell included not less than 20–30 average-size particles and 2–5 large ones. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 817–824, November–December, 2006     

Application of the reduced concentration principle to filled polymers

An investigation has been made into the applicability of the reduced concentration principle to composites based on a partially crystalline polymer — low-density polyethylene — with 13 mineral fillers of different chemical composition, particle size, and porosity. It is shown that over the entire accessible interval of filler load factors the composites investigated obey the law of corresponding states. It is suggested that the deviation of the generalized dependence of the modulus of elasticity from the analogous dependence obtained for amorphous network polymers is associated with a decrease in the crystallinity of the polymer matrix with increase in filler concentration.     

Effect of reaction at the polymer-solid interface on the mechanical properties of alkyd coatings

IR spectroscopy is used to investigate the intermolecular reaction between alkyd resin and the surface of aerosil. It is shown that the nature of the reaction has a considerable influence on the mechanical and adhesion properties of the coatings. Modification of the aerosil surface with octadecylamine leads to the formation of a hydrogen bond between the NH groups of the modifier and the OH groups of the aerosil surface. In the presence of alkyd resin the NH groups are almost completely displaced from the surface of the filler.Mekhanika Polimerov, Vol. 3, No. 1, pp. 19–23, 1967     

Fracture in Ceramic-Matrix Composites Reinforced with Strongly Bonded Metal Particles

The resistance of a ceramic matrix composite to the cleavage cracking across a field of strongly bonded, uniformly distributed metal particles is studied. The crack trapping and bridging effects of the metal particles are analyzed by means of calculating the strain energy and the traction work. An explicit expression for the critical energy release rate as a function of particle volume fraction has been obtained. The fracture resistance is independent of elastic properties of the matrix and the sample geometry and is predominantly determined by the size/spacing ratio of the particles. It is shown that the theoretical curves agree with experimental data quite well. The methodology developed in this article can be used in studying the fracture resistances of composites with high filler contents and irregular filler geometries.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 3, pp. 303–318, May–June, 2005.     

Birefringence and stress-strain diagrams for oriented atactic polymethyl methacrylate and polystyrene films

The stress-strain diagrams of amorphous linear polymers oriented under different conditions are examined; a comparison is made with the parameters of their internal structure. It is shown that the shape of the diagram for rigid polymers is basically determined by the degree of orientation of the links of the macromolecules irrespective of the molecular weight of the polymer and the extension conditions. It is established that the moment of failure can not be determined from this parameter alone. It is found that when the oriented polymer is tested close to the softening point the correlation between the shape of the diagram and the birefringence, characterizing the degree of orientation of the links of the macromolecules, is disturbed.Mekhanika Polimerov, Vol. 2, No. 3, pp. 435–439, 1966     

Effect of filler on relaxation-time spectra of filled polymers

The frequency and temperature dependence of the complex shear modulus G* and tan δ of epoxide compositions with various fillers have been studied. Relaxation-time spectra of filled polymers with various fillers have been plotted by the Ninomi-Ferry method. The principles governing changes in the shape of the spectrum curves with increase in filler concentration have been observed, enabling conclusions to be drawn on the effect of the filler on the change in properties of a polymer matrix and the deformation conditions of the polymer layers between the filler particles.     

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.     

Temperature dependence of the strength of adhesive joints based on crystalline polymer adhesives

The temperature dependence of the stripping strength of adhesive joints between steel and dural plates using crystalline polymers as adhesive (mixed polyamide-4, 5, 8 and guttapercha, both unfilled and filled with an inert filler) has been investigated. The temperature-strength curves pass through two local maxima, near the glass transition temperature of the crystalline adhesive and near its melting point. It is shown that the presence of a high-temperature maximum is determined by recrystallization of the polymer in the overstressed zone at the tip of the developing crack. The relationship between temperature and strength in adhesive joints based on crystalline polymer adhesives is very pronounced in both cohesive and adhesive failure. It is shown that the addition of filler reduces the recrystallization stress of guttapercha.Mekhanika Polimerov, Vol. 1, No. 3, pp. 63–67, 1965