Dynamic Relaxation of Synthetic Fibres

Abstract

The stress regions where amplitude-modulated oscillations (AMO) appear, intensify, weaken, and disappear were determined for PET, Armos, SVM, Terlon synthetic fibres and monofilament PET fibres. The reappearance of AMO caused by the structure of the random copolymer was also found in Armos synthetic fibre. It was found for all fibres investigated that AMO do not appear at temperatures close to the glass transition temperature or any other softening point. A method is proposed for determining the temperature after which AMO do not appear. AMO were also not observed in many synthetic fibres (for example, polypropylene, polyethylene) in the devitrified state. The various explanations of AMO with respect to the structural and kinetic features of oriented polymers, related to the inhomogeneity of the supramolecular structure of oriented polymers, combined with the activating effect of an external load on the relaxation spectrum are examined.In studying the mechanical properties of synthetic fibres by the free longitudinal vibration method, it was found that in rigid-and semirigid-chain oriented polymers SVM, Terlon, Armos, poly(ethylene terephthalate) (PET), a complex form of the oscillation process in the form of amplitude-modulated oscillations (AMO) is observed in a limited load range. The study of this phenomenon shows that after appearing, as the load increases, AMO are initially monotonically intensified, then attenuated and then disappear at some mechanical load. Outside of this load zone, classic damped oscillations, i.e., oscillations without the appearance of AMO, are observed.The shape of the experimentally observed AMO is shown in Fig. 1 for SVM synthetic fibre with a linear density of 29.4 tex. The reappearance of AMO at a higher load was also found for Armos fibre. The stress and strain ranges within which AMO are observed are reported in Table 1.In addition to the load, the temperature affects the character of AMO. It was found that amplitude-modulated oscillations always disappeared at a temperature close to the glass transition temperature. Such an effect can be used for determining this temperature boundary. The validity of the method of determining the indicated temperature boundary is also confirmed by the fact that AMO are not observed in many oriented polymers (for example, in polyethylene and polypropylene fibres) whose glass transition temperature is below room temperature where the free oscillations were measured.Finding AMO in monofilament PET fibres shows that the analyzed phenomenon is not due to the complex structure of the synthetic fibres investigated. The effect of the appearance of AMO in SVM and Terlon fibres with 58.8 tex linear density is also not due to their cross-sectional dimensions.In the stress range within which AMO appear and disappear, the following are observed: the monotonicity of the change in the frequency increases with an increase in the load (Fig. 2a), the mechanical loss characteristic has a sharp maximum (Fig. 2b), and the monotonicity changes twice for the dynamic...

Geothermal heat pump in the passive house concept

“…Numerous studies [1][2][3][4][5][6][7][8][9][10][11][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] carried out in different countries of the world showed the prospect of development in the energy efficiency industry. Broad experience was gained in performing parametric evaluations and successfully developing appropriate passive solutions for different climates.…”

“…Methods of calculating capital costs for additional insulation, operating costs before and after thermal insulation, as well as the payback period of energy-saving measures are described in detail in the works [29][30][31][32][33]. To determine the simple payback, the following basic equation was obtained: (6) where ΔC -capital expenditures, rub.…”

Solutions to Improve the Thermal Protection of the Administrative Building

“…Thus, the heat energy savings will be: -ΔQ ETICS = 367.7 Gcal/year after ETICS application, -ΔQ VFS = 311.5 Gcal/year after VFS application. Methods of calculating capital costs for additional insulation, operating costs before and after thermal insulation, as well as the payback period of energy-saving measures are described in detail in the works [15][16][17][18][19].…”

“…Taking into account the above-mentioned factors, the projected payback period of investment in additional facades insulation is determined by a logarithmic equation [15][16][17][18][19][20]. According to the equation the payback period of energy-saving measures was calculated taking into account the total capital expenditure for its implementation, the rising cost of tariffs for thermal energy (r), discounting future cash flows (i), achieved by cost-cutting as a result of the implementation of energy-saving measures.…”

Complex non-exponential form of damped vibrations in uniaxially oriented polymeric materials with one mechanical degree of freedom

“…Previously, in (Romanova et al 2000;2007b;Rymkevich et al 2014) for a number of studied polymer threads (SVM, lavsan, terlon, etc. ), it was found that in a certain range of mechanical stresses (or levels of static deformation) a complex non-exponential form of damped oscillations or beats schematically presented in Fig.…”