Estimation of the length distribution of through polymer chains

The contributions of entropy and elastic forces to the tensile modulus of a polymer chain are estimated. The chain length-distribution function in the amorphous region of highly oriented Lavsan is approximately determined from macroscopic stress-strain dependence. It is found that the length distribution has a width of the order of several percent of the length of the amorphous region of the fibril.A. F. Ioffe Physicotechnical Institute, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 922–925, September–October, 1974.     

Calculation of damage and of force relaxation in amorpho-crystalline polymers

The dynamics of damage and of the relaxing force in amorpho-crystalline polymers under constant strain are calculated using the formulas for the probability of rupture of a deformed polymer molecule and a model representation of amorphous interlayers. The main parameters of the model are the maximum and minimum possible deformations of molecular chains, the energy of rupture activation, the function of the chain length distribution, the temperature, the macroscopic strain, and the relative dimensions of the amorphous interlayer. The conformity of the theoretical model and the association of the relaxation spectrum with the internal molecular and structural characteristics of the material are established.Zhambyl Technical Institute of Light and Food Industry, Taraz, Kazakhstan. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 4, pp. 499–508, July–August, 1999.     

Mechanics of a polymer chain stretched in an amorphous region of an amorphous-crystalline polymer. Effect of external crystal boundaries

The tensile load on a polymer chain extending across an amorphous region of an amorphous-crystalline polymer, from one crystal to another, has been calculated theoretically. The analysis is carried out for the case of large extensions of the amorphous region, when it is necessary to take into account the conditions of anchorage of the chain at the external boundaries of the crystals. A rigorous criterion has been established for the applicability of an earlier theory [1] in which the external boundaries were not taken into consideration. It is concluded that the critical load on the chains cannot be reached in that model in the range of deformations of the amorphous region studied. It is noted that the expression for the displacement of the chain segments is a solution of the Frenkel-Kontorov model of a point dislocation in a crystal with a boundary.Mekhanika Polimerov, Vol. 2, No. 5, pp. 664–670, 1966     

Small deformations of oriented polymers

On the basis of a phenomenological analysis of the temperature dependence of the modulus of instantaneous elasticity and the stress relaxation process, it is suggested that in the region of small deformations there are no breakages of the macromolecules that might affect the elasto-relaxational behavior of highly oriented polymers (fibers) as in the region of large deformations. To judge from the values obtained for the energy constants, these properties are determined by the number of intermolecular bonds in the amorphous regions (modulus of instantaneous elasticity) and the physical events associated with the reorganization of these bonds and hindered rotation of the chain units (relaxation process).S. M. Kirov Leningrad Institute of Textiles and Light Industry. Translated from Mekhanika Polimerov, No. 6, pp. 976–980, November–December, 1971.     

End defects in crystalline polyethylene. 1. Statement of the problem and modeling of the steric structure of end defects

Conclusions 1. Changes in the conformations of polyethylene molecules around the end of a neighboring chain and around the ends of two neighboring chains have been determined on an electronic calculator for various directions of end bending.2. It has been ascertained that a column of bivacancies disappears with simultaneous formation of spiral dislocations at smaller distances from the chain end to the crystallite surface than in the case of a single-vacancy column.3. Energies of formation of end defects and the bonding energy of defects upon aggregation have been calculated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 400–407, May–June, 1978.     

Elasticity of the intercrystallite zones and the mechanical properties of oriented polymers

As a result of a study of the behavior under load of the elements of the supermolecular structure of oriented amorphous-crystalline polymers it is shown that the stresses on the crystallites and the amorphous zones in series with them in the direction of the chain axes are equal to the mean stress applied to the specimen along the orientation axis. The nature of the elasticity and deformability of the amorphous zones is analyzed. A relation is obtained between the strength properties of oriented polymers and the number of load-carrying chains in the amorphous zones.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 1002–1007, November–December, 1969.     

Terminal defects in crystalline polyethylene

Conclusions 1. It was shown that the terminal defect in polyethylene contains a set of partial twist disclinations with different Frank vectors for different chains.2. It was found that the structure of the terminal defect changes during elongation of the chain and outward from the crystallite. It was also found that the volume of the void formed by the presence of the chain and remains constant; the elongation process is accompanied by a conservative motion of the disclination loops along the chains, which causes creep of the screw dislocations.3. The conformational changes were calculated for a segment moving in the crystal field of neighboring chains in regular and high-pressure PE; the values of the energy of activation of the chain and motion were obtained (10.3·10^–16 and 3.6·10^–16 erg/monomer for the regular and high-pressure PE, respectively), indicating a higher rate of annealing of PE in the high-pressure phase.For communication II, see [2].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 793–798, September–October, 1978.     

An experimental study of the deformation of multilayer cylindrical shells

Experimental results are presented on the deformation of two-layer and four-layer reinforced shells subject to static loading. The strains on the outside and inside surfaces are unequal at points remote from the region of the edge effect when the shell is subject to an internal pressure and an axial force.P. I. Baranov Central Institute for Aviation Engine Design. Translated from Mekhanika Polimerov, No. 5, pp. 943–944, September–October, 1973.     

Strength of rigid oriented amorphous polymers

A method is proposed for obtaining uniaxially oriented specimens of amorphous unfractionated polymer with a particular oriented chain length. The length of the oriented chains and their molecular weight M_c depend importantly on the conditions under which the polymer is stretched. It is shown that the strength of specimens obtained by stretching at constant M_c increases linearly with the relative fraction of oriented phase. The slope of this linear relation increases with the length of the oriented molecular chains. The ratio of the maximum strength of fully oriented polystyrene to the strength of the unoriented material is found to be 78 instead of the value of 6 given in [6].Mekhanika Polimerov, Vol. 3, No. 6, pp. 1048–1053, 1967     

Effect of orientation and molecular weight on the modulus of elasticity of polymer materials

The modulus of elasticity of a perfectly crystalline polymer is calculated as a function of the orientation of the crystallites. The calculations are based on the mechanics of a micro-inhomogeneous continuum. The dependence of the modulus of elasticity on crystallite orientation and molecular weight is calculated with reference to the example of crystalline kapron.Moscow-Lenin Pedagogical Institute. Problem Laboratory of Polymer Physics. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1002–1007, November–December, 1968.     

Calculation of the residual stresses and strains in wound reinforced-plastic products

A method is proposed for determining the residual stresses and strains in wound glass-reinforced plastic products. The fabrication process is divided into five stages: winding, heating polymerization, cooling, and removal from the mandrel. The initial stresses that develop during winding and the subsequent stress increment associated with heating are taken into account. Polymerization is treated as a process during which the mechanical and thermophysical properties of the material change. Chemical shrinkage of the resin and its filtration through the fiberglass are disregarded. Equations are derived for the residual radial and peripheral stresses in the finished product, for the residual change in inside diameter, and for the temperature at which the product is released from the mandrel during the cooling process. The experimental data relating to two types of wound products are discussed. The results of a computation of the residual stresses and the residual changes in inside diameter are compared with the experimental data.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 134–139, January–February, 1969.     

Elastic recovery of filled rubber mixtures after extrusion through round ducts

The results of an experimental study on the elastic recovery of filaments of filled rubber mixtures extruded through round ducts of various length are discussed. An empirical relationship which permits the effect of elastic recovery of filaments of a rubber mixture after extrusion from a round duct to be estimated as a function of the relative duct length has been established from the data measured.All-Union Scientific-Research and Technological Design Institute of the Rubber Industry, Volzhskii. Translated from Mekhanika Polimerov, No. 2, pp. 364–268, March–April, 1975.     

Contribution to the theory of the elastic properties of amorphous-crystalline polymers

The elastic constants of an amorphous-crystalline polymer are calculated from the known values of the elastic constants of its amorphous and crystalline components.Moscow Lenin Pedagogical Institute, Problem Laboratory of Polymer Physics. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 213–218, March–April, 1969.     

The theory of orientational drawing of linear amorphous polymers

On the basis of modern ideas on the structure of linear, amorphous polymers a model of a molecular, three-dimensional network with temporary cross-links and van der Waals interaction between the chains is presented. Using this model as a starting point, a differential equation for the deformation of a linear, amorphous polymer in the viscoelastic state is derived. The differential equation for the orientation of a linear, amorphous polymer, which describes the evolution of distribution functions for statistical segments, is obtained. Previously obtained results follow from this theory as special cases.V. I. Lenin State Pedagogic Institute, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1021–1028, November–December, 1974.     

Study of mechanical relaxation processes in ladder organosilicon polymers

Dynamic viscoelastic properties of ladder polyorganosiloxanes have been studied by the method of induced resonance oscillations in the temperature range from –150 to 300°C and in the frequency range from 8 to 300 Hz. Two broad maxima of mechanical losses were observed for all the polymers studied independently of their chemical structure, a low-temperature maximum in the –150 to 0°C region and a high-temperature maximum in the 0 to 250°C region. It was found that the introduction of alkyl groups into polyphenylsilsesquioxanes does not noticeably affect the position and nature of the low-temperature relaxation peaks but in certain cases leads to an increase in the dynamic modulus in polyphenylalkylsilsesquioxanes, compared with the modulus of polyphenylsilsesquioxane in the same temperature region. In the high-temperature region, a distinct dependence is observed of the relaxation peak on the length and the content of alkyl groups in the polymer. It has been found that increase in the length and the content of alkyl groups is accompanied by a shift in the peak in the direction of low temperatures and a decrease in the value of the modulus. Hypotheses have been suggested on the nature of the shifts which lead to the relaxation peaks observed in the ladder polyorganosiloxanes.Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 804–809, September–October, 1973.     

Comparative estimate of the molding capacities of injection molding machines with plunger and screw plastication

An analysis of the mold filling process, based on the equation of nonisothermal flow of an amorphous polymer melt, shows that for thin moldings the molding capacity of the machine, estimated as the maximum shot length, has a limit that does not depend on the pressure at the mold inlet and is determined by the flow rate of the polymer in the mold. As shown by an analysis of the process of compaction of the polymer in the system preceding the mold, this flow rate is many times less for plunger plastication, which is responsible for the reduced molding capacity of plunger machines. The effect can be eliminated by compressing the polymer before injecting it into the mold.Moscow Institute of Chemical Machine Building. Translated from Mekhanika Polimerov, No. 2, pp. 367–372, March–April, 1970.     

On the theory of infrared dichroism of oriented amorphous polymers

A network model of a linear amorphous polymer is used as a basis for calculating the infrared dichroism of uniaxially and biaxially oriented material. The dependence of the dichroism on the uniaxial and biaxial stretch ratios, orientation temperature, and certain other factors is investigated. Previously published experimental data are discussed.Moscow Lenin State Pedagogical Institute, Problem Laboratory of Polymer Physics. Translated from Mekhanika Polimerov, No. 6, pp. 979–984, November–December, 1970.     

Prediction of the short-term strength of polymer materials based on equations of state

The possibility is analyzed of using equations of state for predicting the mechanical properties of linear amorphous polymers with short-term loading from data for their compressibility.D. I. Mendeleev Chemical Technology Institute, Moscow. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 2, pp. 258–262, March–April, 1997.     

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.     

Deformation of the glass in the zone of formation of a hollow glass fiber

An equation has been derived for the deformation of the glass in the zone of formation of a hollow glass fiber, and the nature of the deformation along the length of the "bulb" has been determined. The principal technological factors controlling the capillarity coefficient of the fiber have been established and their interactions are shown to affect the geometric characteristics of the fiber. The region of existence of the hollow fiber formation process has been determined. There is satisfactory agreement between the experimental and theoretical data.All-Union Scientific-Research Institute of Glass-Reinforced Plastics and Glass Fiber, Moscow Region. Translated from Mekhanika Polimerov, No. 4, pp. 599–603, July–August, 1973.