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1.
It is shown that the sign of the linear coefficient of thermal expansion is determined by the configuration and direction relative to the deformation axis of the molecular chains in the amorphous and crystalline phases of the polyethylene. An increase in orientation leads to a decrease in shrinkage temperature. The presence of a dispersed inorganic filler results in the formation of fibrillar structures in the polyethylene.  相似文献   

2.
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.  相似文献   

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It is shown that, as the elastic deformation of the polymer increases, the number of gauche isomers in oriented polyethylene fibers decreases linearly.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 170–172, January–February, 1970.  相似文献   

4.
Conclusions Among the two configurations discussed, the beam has a rather theoretical importance, as an extension and generalization of the cracked beam problem. Unlike this, embedded delaminations can be found often in real constructions. The fact that the maximum value of SERR vs. fibre orientation angle curve for the circular embedded delamination is surpassed by that for the split beam only by three times and by that for the split beam under mode II loading approximately six times means that an embedded delamination can lead to difficulties when the plate is tensed (or compressed — even in an underbuckled state — within the linear approach the non-opening modes of stress concentration will just change their signs when the load changes its sign), especially under a cyclic loading. Of course, the shell model used is fairly rough and does not take in account several features or real delaminations extension and does not allow one to evaluate properly the stress field near the crack front; thus, more analytical and experimental studies would be needed, to establish the crack development process. The 3D analysis is necessary when initiating delaminations are studied, for the beam/plate assumptions can no longer be regarded as necessary since the delamination linear dimensions are comparable to or less than the thickness of the sublaminate.Published in Mekhanika Kompozitnykh Materialov, Vol. 31, No. 1, pp. 45–50, January–February, 1995.  相似文献   

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Large-angle x-ray diffraction and infrared spectroscopy have been used to investigate the behavior of the crystalline zones in oriented polymers under load. It is shown that under the influence of a load applied along the axis of orientation the crystallites are partially destroyed, the more so the greater the applied stress. For different polymers the destruction of the crystallites is the greater the weaker the intermolecular bonds. The stability of the crystallites is improved by orientation.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 516–520, May–June, 1976.  相似文献   

7.
The formation of supermolecular structure has been investigated in the case of medium-pressure polyethylene film subjected to a dose of 30 Mrad of n, radiation. The melt, prestretched at 160°C to various degrees of elongation , was crystallized at constant temperature. The results are interpreted on the basis of an analysis of the effect of the mechanical field on the growth kinetics and the orientation relative to the direction of extension of the individual crystallites; the first factor determines the shape and the second the sign of the spherulite.Institute of High-Molecular-Weight Compounds, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 3–6, January–February, 1971.  相似文献   

8.
The results from experimental and theoretical investigation of the creep of polyethylene terephthalate film during stepwise varying stresses under conditions of uniaxial extension are given.Izhevsk Mechanical Institute. Translated from Mekhanika Polimerov, No. 5, pp. 929–933, September–October, 1972.  相似文献   

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Disks of polyethylene of different density were subjected to plane tensile deformation along eight axes. It was established by volume dilatometry that the melting interval of the deformed plates had been shifted into the region of higher temperatures. It follows from the behavior of the specific volume increment associated with melting that deformation leads to the destruction of some of the low-melting structures and increases the content of higher-melting structures.Lugansk Machine-Building Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1102–1104, November–December, 1970.  相似文献   

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The strength of the joints arising as a result of the mutual deformation of polyethylene specimens is studied, and it is shown that mutual deformation can lead to the formation of a strong joint.Mekhanika Polimerov, Vol. 2, No. 4, 574–579, 1966  相似文献   

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The development of submicroscopic cracking under load has been studied (by a small-angle X-ray scattering technique) in such oriented polymers as Kapron (Nylon 6), polypropylene, etc. The increase in crack density (Ncr) is compared with the variation of the tensile strain (). The observed correlation between and Ncr indicates that the processes of fracture and deformation of oriented polymers are closely connected. The presence of a similar correlation in loading-relaxation-repeat loading experiments establishes fracture as the primary process.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 43–47, January–February, 1970.  相似文献   

17.
The deformation of an orthotropic glass-reinforced plastic is considered with allowance for the failure of the resin in the transverse layers.Ordzhonikidze Moscow Aviation Institute. Translated from Mekhanika Polimerov, No. 1, pp. 144–147, January–February, 1970.  相似文献   

18.
Optical microscopy has been used to investigate the development of a slit in polyethylene and polypropylene films with spherulites of different types and sizes stressed in uniaxial tension. The angle between the slit and the direction of extension was 0, 45, or 90°. Slits at 45 and 90° initially develop through localization of slits by a stronger oriented polymer and subsequently as a result of failure of the oriented polymer at the tip of the slit. A longitudinal slit does not develop and does not affect the deformation of the film.Mekhanika Polimerov, Vol. 3, No. 1, pp. 95–98, 1967  相似文献   

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Results are presented of studies on melts of batches of polyethylene differing in overall molecular weight and branching. For high-density polyethylene, unlike the low-density material, the ratios between the tangential and normal stresses and between the constituents of the composite dynamic shear modulus are independent of temperature. A close agreement has been found between the total and net viscosity with cyclic vibration frequencies equal to the steady shear rate.  相似文献   

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