Effect of supermolecular structure on deformation and strength properties of low-pressure polyethylene

The effect of the supermolecular structure on the mechanical properties of polyethylene was studied. A change in the structure of films was achieved by varying the isothermal crystallization conditions. Films have been prepared from low-pressure polyethylene (LPPE) which have fine spherulitic and lamellar structures. It has been demonstrated that the strength of unorientated films with a fine spherulitic structure is twice that of unorientated lamellar specimens. This difference in the strengths was also retained after orientational elongation to 20 times the length at a high temperature (102°C). The conclusion was reached that the casting of LPPE plays an important part in preparing high-strength orientated polyethylene films.A. F. Ioffe Physicotechnic Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 963–966, November–December, 1972.     

Predicting the endurance of ceramics from the results of verification tests

Mechanics of Composite Materials -     

Predicting the porosity of glass-reinforced plastics from their thermal conductivity

The effect of porosity, reinforcement ratio and specific weight on the thermal conductivity of a series of glass-reinforced plastics has been investigated. It is shown that, if the thickness, the weight characteristic (weight per square meter), and the number of layers of reinforcing fabric are known and the thermal conductivities of the components are constant, then the porosity of the glass-reinforced plastic can be predicted from its thermal conductivity. Data on the relation between the specific weight and the thermal conductivity of the glass-reinforced plastics investigated are presented.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 522–525, May–June 1971.     

Predicting performance measures for Markovian type of manufacturing systems with product failures

Optoelectronic products are typically assembled and tested in a flow shop environment with multiple processors at each stage. The first few stages are dedicated for assembly and the later stages are dedicated for calibration and testing. Whenever a product (or job) fails at a stage, it is routed back to one of the downstream stages or to the same stage (depending upon the nature of the failure). Consequently, the product could circulate several times between the current stage and the preceding stage(s) before moving to the next stage. Estimating the performance measures (such as WIP and flow time) of such manufacturing systems is not trivial. This paper presents analytical approximations to estimate the performance measures of a manufacturing system with multiple product classes, job circulations due to failures, and some resources being shared among different product classes. The analytical approximations were verified using simulation on several problem instances. The experimental study indicates that these approximations can be used by operations managers to estimate the performance measures of a manufacturing system with product failures.     

Relaxation dynamics of the rheological properties of ferrofluids

We studied experimentally the shear stress relaxation of two different ferrofluids under the action of an external magnetic field by stepwise changes of shear rate. It has been found that ferrofluids able to form significant structures under the influence of an applied magnetic field show a slow relaxation phenomenon. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Predicting the outcomes of conflicts

We study and solve problems involving the optimization of instructional information connected with the problem of predicting the outcome of conflicts. Translated fromDinamicheskie Sistemy, Vol. 11, 1992.     

Increasing the optical anisotropy of polyethylene spherulites

The authors show that in some cases chemical modification leads to an increase in the optical anisotropy of polyethylene spherulites; this phenomenon can be used to obtain additional information on the structure and growth of the spherulites.Institute of the Mechanics of Metal-Polymer Systems, Academy of Sciences of the Belorussian SSR, Gomel'. Translated from Mekhanika Polimerov, No. 2, pp. 343–344, March–April, 1974.     

Predicting the deformation properties of polymers

Physically well-founded relations, following from a consideration of the molecular-kinetic nature of the relaxation processes, are proposed for the time-temperature superposition principle. It is shown that the well-known Williams—Landel—Ferry relation is a particular case of more general formulas.V. I. Lenin Moscow State Pedagogical Institute, Problem Laboratory of Polymer Plastics. Translated from Mekhanika Polimerov, No. 6, pp. 1106–1109, November–December, 1971.     

Predicting the future of scholarly publishing

Conclusions  What should we conclude? Should we steadfastly maintain the status quo? Do we avoid technology altogether? Of course not.We should experiment; we should try out new things; we should tinker with technology and find better ways to communicate. This article is based on a talk given at the Conference on Electronic Information and Communication, Tsinghua University, China, August 29-31, 2002. A version of this paper will appear in the proceedings of that conference.     

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.     

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.     

Determination of the rheological characteristics of polymer materials from the static σ-ε curves and creep and relaxation curves

A method is proposed for determining the rheological characteristics of polymer materials from the experimental - curves and the creep and relaxation curves, when the behavior of the material is described exactly and approximately by the equation of a standard solid, together with a method of determining the conditional rheological characteristics when only a certain section of these curves is approximately described by the equation of a standard solid. The proposed method makes it possible to eliminate the ambiguity in the determination of the rheological characteristics due to difficulties in the exact determination of the coordinates of the beginning and end of the static curves. The use of conditional rheological characteristics makes it possible to describe the behavior of polymer materials over a broad time interval under static loading conditions by means of the equation of a standard solid without resorting to the use of complex spectral functions. A relation is established between the spectral viscoelastic functions and the conditional rheological characteristics.Mekhanika Polimerov, Vol. 3, No. 6, pp. 977–988, 1967     

Predicting DAX trends from Dow Jones data by methods of the mathematical theory of democracy

The mathematical theory of democracy operates on the indices of popularity and universality which are used to find socially optimal representatives and representative bodies. Regarded mathematically, neither the ‘society’, nor its ‘representatives’ are necessarily human, so that some objects can represent the behavior of other objects. This idea is applied to predicting the DAX-trends (German stock index) from the actual Dow-Jones data; the current fluctuations of stock prices in New York are regarded as representative indicators of future stock price fluctuations in Frankfurt. In particular, it is found that American Express anticipates on the average the price ±fluctuations of 2/3 of the DAX stocks. The statistical significance of the null hypothesis that such a bias from the uncertainty 50% can occur by chance is only 3.5%.     

Calorimetric investigation of the tensile deformation of polyethylene

A calorimetric apparatus for investigating the thermal effects associated with tensile deformation is described. The results of calorimetric measurements made on high- and low-density polyethylene during the deformation process are presented. It is shown that on the interval of strains and loading rates investigated the deformation of polyethylene is energetic in character.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 579–584, July–August, 1970.     

Study of the autoadhesion of polyethylene -polyisobutylene compositions

The autoadhesion of polyethylene-polyisobutylene compositions is shown to depend importantly on contact pressure. The introduction of a filler may increase or reduce the autoadhesion of the composition. The experimental results are explained in terms of the diffusion theory of autoadhesion.Moldavian Scientific-Research Institute of the Food Industry, Kishinev. Translated from Mekhanika Polimerov, No. 3, pp. 532–534, May–June, 1971.     

Electron-fractographic investigation of the brittle fracture of polyethylene

The results are presented of an electron-microscope investigation of the brittle fracture of linear polyethylene at the temperature of liquid nitrogen. It is shown that the physical nature of the structural details of the microrelief of the fracture surface is conditioned by local plastic deformation of the stratified lamellar structures in a thin layer adjacent to the fracture surface preceding and accompanying fracture. The possibility of local self-heating is discussed and a possible mechanism of plastic deformation of the crystal platelets at low temperatures is proposed.Mekhanika Polimerov, Vol. 3, No. 2, pp. 286–290, 1967