Chain Polymer Molecules Research Articles

A binary eutectic electrolyte design for high-temperature interface-compatible Zn-ion batteries

The deterioration of aqueous zinc-ion batteries (AZIBs) is confronted with challenges such as unregulated Zn2+ diffusion, dendrite growth and severe decay in battery performance under harsh environments. Here, a design concept of eutectic electrolyte is presented by mixing long chain polymer molecules, polyethylene glycol dimethyl ether (PEGDME), with H2O based on zinc trifluoromethyl sulfonate (Zn(OTf)2), to reconstruct the Zn2+ solvated structure and in situ modified the adsorption layer on Zn electrode surface. Molecular dynamics simulations (MD), density functional theory (DFT) calculations were combined with experiment to prove that the long-chain polymer-PEGDME could effectively reduce side reactions, change the solvation structure of the electrolyte and priority absorbed on Zn(002), achieving a stable dendrite-free Zn anode. Due to the comprehensive regulation of solvation structure and zinc deposition by PEGDME, it can stably cycle for over 3200 h at room temperature at 0.5 mA/cm2 and 0.5 mAh/cm2. Even at high-temperature environments of 60 °C, it can steadily work for more than 800 cycles (1600 h). Improved cyclic stability and rate performance of aqueous Zn||VO2 batteries in modified electrolyte were also achieved at both room and high temperatures. Beyond that, the demonstration of stable and high-capacity Zn||VO2 pouch cells also implies its practical application.

Enhanced luminescent properties of poly(sodium acrylate)-based composite and its selective interaction towards copper ions

This study investigates the luminescent properties and metal ion interactions of europium when combined with a polymer chain of poly (sodium acrylate) (PSA) and a phenanthroline (Phen) molecule, which acts as an efficient antenna. The study of interactions between lanthanide ions and various compounds in different matrices is crucial, providing valuable insights into the molecular environment, and enabling a deeper understanding of processes affecting their luminescence. In this study, we investigated the luminescent properties of the Eu(PSA)Phen complex and its remarkable capacity for selective interaction with Cu2+ ions in an aqueous solution. From this selective interaction, we conducted a series of detailed studies that provided valuable insights into the mechanisms of luminescence suppression, information about the europium chemical environment, and other related aspects. The luminescence of Eu(PSA)Phen is significantly quenched by Cu2+ ions, driven by both static and dynamic mechanisms. The presence of the PSA polymer chain and Phen molecules within the composite exerts a profound influence on energy transfer processes, enabling selective responses to Cu2+ ions, even in the presence of competing cations. Additionally, we observed a preferential interaction of the PSA molecule in the Eu(PSA)Phen composite with Cu2+ ions over the N groups of phenanthroline. These findings underscore the compound potential as a versatile tool in various fields, ranging from material science to biosensing, where rapid and selective metal ion detection is of paramount importance.

Formation of zinc phthalocyanine on polymethyl methacrylate chain: Its nanographene‐based composite, thermal, electrical and optical behaviors

AbstractPoly[4‐((4‐vinylbenzyl)oxy) phthalonitrile‐co‐methyl methacrylate] [P(VBOPN10.7%‐co‐MMA)] was prepared by atom transfer radical polymerization (ATRP) method at 110°C. Green colored single chain polymer molecule via intramolecular formation of zinc phthalocyanine (SCP‐ZnPc) on polymer chain was synthesized using VBOPN as a precursor copolymer under conditions of dilute cyclohexanol and at 140–150°C. The successful formation of zinc phthalocyanine on a single chain molecule was confirmed using Fourier‐transform infrared spectroscopy (FT‐IR) and UV/Vis spectroscopy techniques. Nanogaphene‐based SCP‐ZnPc composite was prepared to employ 6 weight (wt)% of total weight and were investigated its thermal, electrical, dielectric and optical properties. The dielectric and DC electrical conductivity of SCP‐ZnPc/NG 6 wt% nanocomposite were found to increase depending upon temperature. And the conduction obeyed the Arrhenius relationship with the activation energy, Ea values for I. and II. regions were 0.345 eV and 0.275 eV, respectively. The optical constants (refractive index, real value of optical dielectric constant) and the optical band gap of SCP‐ZnPc/NG 6 wt% were estimated. The direct band gap and refractive index of SCP‐ZnPc/NG 6 wt% were estimated, and its direct band gap was estimated as 2.7 eV.

Adsorption Affinity of Linear and Aromatic Organic Anions Competing for Cationic Cement Surfaces.

Competitive adsorption of chemical admixtures onto cement is of critical importance in delivering bulk performance requirements of cement slurries employed in constructing high-performing structures, like oil wells. This challenge is complex to investigate, because of the many variables that include the heterogeneity, high pH, and ionic strength of cement fluids; the multiple crystalline phases present in unhydrated and set cement; and the high number of admixtures required to meet performance criteria in commercial operations. The purpose of this study is to relate chemical structures to relative adsorption behavior of admixtures onto cement when present together and classify such interactions as beneficial (synergistic) or detrimental (antagonistic). Adsorption characteristics of single admixtures were examined by total organic carbon analysis, FT infrared spectroscopy, scanning electron microscopy, calorimetry, and UV/vis spectrophotometry. Results show that the adsorption of single chemical admixtures follows the order of monomeric hydroxycarboxylate molecule > sulfonated linear polymer > sulfonated aromatic polymer > carboxylated/sulfonated linear polymer > carboxylated branched polyether polymers. The observed adsorption behavior of polymers correlates extremely well with the order for cement hydration retardation, with carboxylated polymers being the most powerful retarders. Results correlate closely with the proposed mechanism that sulfonated polymers adsorb onto aluminate phases, presumably the tricalcium aluminate phase; and the carboxylate polymers onto silicate phases, particularly the predominant tricalcium oxysilicate phase. The hydroxycarboxylic monomeric molecule was the strongest retarder of all and has the highest adsorption level, presumably on tricalcium oxysilicate. The competitive adsorption behavior in binary mixtures was studied by monitoring the displacement of a signaling polymer by a second admixture. Results indicate that, for similar functional groups, shorter polymers are competitively more strongly adsorbed than longer chain molecules and that the shorter chain polymers were not desorbed significantly by longer chain polymer molecules. Rheological measurements correlated admixture adsorption behavior to the observed slurry fluidity.

Evolution of the absorption edge of PET films irradiated with Kr ions after thermal annealing and ageing

This paper presents the results of a study of the ageing and annealing of films of polyethylene terephthalate (PET) after irradiation with Kr ions. For the studies of ageing, PET film samples were irradiated normally to the surface with Kr 15+ ions of energy of 1.75 MeV/a.u. and various fluences between (1–10)x10 10 cm −2 and then kept for 7.5 months (5400 h) at room temperature in the dark in sealed cases with air removal. The studies of annealing were made on a PET sample irradiated with Kr 13+ ions of energy 1.2 MeV/a.u. at an angle of 40° to the normal and a fluence of 5 × 10 10 cm −2 . Annealing was carried out in the dark in sealed cases with air removal for 160 and 500 h at a temperature lower than the glass transition. UV/vis/near IR differential spectra were obtained for each sample in the wavelength range 308–1050 nm (photon energy 4.03–1.18 eV). We used an established technique to obtain interference-free transmission curves T(λ) for both pristine and irradiated PET film samples and a differential spectroscopy technique to obtain differential transmission spectra ΔT(λ) of the changes in transmission after ageing and annealing. For all samples, a region of increased transmission at short (UV) wavelengths and a region of reduced transmission at longer (red/near IR) wavelengths were observed. These changes result from, respectively, the decay of the smallest irradiation-induced chromophores that are responsible for the absorption of short-wave radiation and the growth in the numbers and size of chromophores with larger conjugation values. They confirm our previous experiments showing that swift heavy ion irradiation of PET films creates reversible non-covalent π–π c onjugation bonds between neighbouring chain molecules in polymer films. These results also confirm our hypothesis that under annealing and ageing the smallest, least stable irradiation-induced conjugations decay while larger, more stable, conjugations grow. Our results also indicate that oblique irradiation, for which the electric field vector has a significant component perpendicular to the film texture, can enhance the polarization effects of the interaction of neighbouring polymer chain molecules leading to electro-optical amplitude enhancement. • Evolution of the absorption edge of PET films irradiated with Kr ions. • PET sample irradiated with 84 Kr 13+ ions of energy 1.2 MeV/a.u. and fluence of 5 × 10 10 cm −2 at an angle of 40° to the normal. • Electro-optical studies of the effect of an electric field on the optical properties. • Analyze the UV–Vis spectro-interferograms.

Effects of graphite oxide on thermal and electrical behaviors of coumarin‐based methacrylate copolymers: Its single chain polymer molecule via intramolecular cyclobutane formation

AbstractThe random copolymers of methyl methacrylate (MMA) and 4‐methyl‐2‐oxo‐2H‐chromen‐7‐yl methacrylate (COUMA) [poly (COUMA0.49‐co‐MMA)] (COMCOP1) and [poly(COUMA0.36‐co‐MMA)] (COMCOP2) were prepared via the conventional radical polymerization method. The copolymers were characterized by 1H‐NMR, Fourier‐transform infrared spectroscopy (FT‐IR), UV–visible (UV–vis), thermogravimetric analysis, and differential scanning calorimetry instruments. A kinetic study of the thermal decomposition of COMCOP1 and COMCOP1/GO 16 wt% was investigated using thermogravimetric analyzer with non‐isothermal methods selected for analyzing solid‐state kinetics data. The average activation energy values were calculated via Flynn Wall and Ozawa (FWO) and Kissinger‐Akahira‐Sunose models in a period of α = 0.10–0.70. The average values of activation energy obtained from Kissinger method for COMCOP1 and COMCOP1/GO 16 wt% were 94.5 and 78.4 kJ/mol, respectively, whereas, those of estimated by FWO method were 103.5 and 87.0 kJ/mol. We indicate that well‐defined single chain polymer molecule (SCPM) via intramolecular cyclobutane formation could be obtained by the intrachain photodimerization of coumarin groups during UV irradiation at 365 nm diluted solution of COMCOP1. The photodimerization of coumarin groups in the copolymer was confirmed by UV–vis, FT‐IR, and 1H‐NMR instruments. Dielectric and electrical behaviors of the composites having a semiconductor behavior filled GO were investigated. The activation energy values based on dc conductivity for COMCOP1 loaded GO 10 and 12 wt% were decreased from 0.206 to 0.069 eV. Also, the Ea values estimated for COMCOP2‐loaded GO 12 and 13.6 wt% were 0.0580 and 0.0859 eV, respectively.

Opening of a weak link of a closed looped polymer immersed in solution. Analytical modelling using a delta function sink

We present an analytical approach in order to investigate the theory for opening of a weak link of a long chain closed polymer molecule when present in dilute solution. In general the process of formation of end loops in long chain polymer molecule has received appreciable interest in many research areas. The opposite processes of breaking open of a loop is equally important but has been less explored. Thus researchers are trying to formulate analytical model for the phenomenon. We give analytical model for calculation of rate constants of the process. The physical problem of opening of a weak link can be analytically traced by a Smoluchowski-like equation. It has a reactive Dirac delta function sink of finite strength which takes care of the possible window of reaction. The two rate constants, the long term rate constant (kL) and the average rate constant (kI) are derived from the survival probability. We find that kL is independent of initial distribution, so for both loop closing and loop opening reaction the expression for kL is same, but that is not the case for kI.

Methane Detection with a Tungsten‐Calix[4]arene‐Based Conducting Polymer Embedded Sensor Array

AbstractThe detection of methane is important for industry, environment, and our daily life, but is made challenging by its small size, high volatility, and nonpolar nature. Herein, a tungsten‐capped calix[4]arene‐based p‐doped conducting polymer with hexafluorophosphate or perchlorate counter‐anions as a transducer is used to detect methane in dry air. The host–guest interaction between calixarene moieties within the polymer chain and methane molecules leads to the resistance variation of the polymer. The experimental limit of detection (LoD) of methane for the polymer‐based sensor is demonstrated to be less than 50 ppm at room temperature, and the extrapolated theoretical LoD of 2 ppm represents exceptional sensitivity to methane. Furthermore, the discrimination of methane from interfering volatile organic compounds is achieved by exploiting a sensor array using complementary chemiresistors and principal component analysis.

Direct numerical simulations of turbulent viscoelastic jets

Direct numerical simulations (DNS) of spatially evolving turbulent planar jets of viscoelastic fluids described by the FENE-P model, such as those consisting of a Newtonian fluid solvent carrying long chain polymer molecules, are carried out in order to develop a theory for the far field of turbulent jets of viscoelastic fluids. New evolution relations for the jet shear-layer thickness , centreline velocity and maximum polymer stresses are derived and validated by the new DNS data, yielding , , and , respectively, where is the coordinate in the streamwise direction. It is shown that, compared with a classical (Newtonian) turbulent jet, the effect of the polymers is to reduce the spreading rate, centreline velocity decay, Reynolds stresses and viscous dissipation rate. The self-preserving character of the flow is analysed and it is shown that profiles of mean velocity, Reynolds stresses and polymer stresses are self-similar provided the proper scales are used in the normalisation of these quantities. A fundamental difference from the Newtonian jet in this regard is the necessity for two, instead of only one, different velocity and length scales to properly characterise the evolution of the turbulent flow. These extra velocity and length scales are directly related to a time scale associated with the characteristic fading memory property of viscoelastic fluids.

Ion Charge Influence on the Molecular Structure of Polyethylene Terephthalate Films after Irradiation with Swift Heavy Ions

We report here experimental results investigating the influence of the initial swift heavy ion charge on the structure of polyethylene terephthalate (PET) film after irradiation, using a structurally sensitive X-ray diffraction method. Kr ions with an energy of 100 MeV and charges of 13+, 14+, and 15+ were each used at irradiation fluences of 5 × 1010, 7.5 × 1010, 1 × 1011, 2.5 × 1011 and 5 × 1011 ions/cm2. At constant energy and irradiation fluence, the post-irradiation structural changes in PET film show a clear dependence on the initial ion charge. As either the fluence or ion charge increase, the latent tracks begin to overlap, leading to cross-linking of PET chain molecules to form rotational isomers (rotamers). We use the fluence corresponding to the onset of overlapping to estimate the size of latent tracks for different ion charges. At the highest fluences, the latent tracks become entirely overlapped, and the interchain cross-linking extends throughout the whole film. Since this cross-linking is due to the dipole–dipole interaction of subunits of repeat units of PET chain molecules, it is reversible, in contrast to the well-known chemical cross-linking of polymer chain molecules under irradiation.

Understanding the reversible looping kinetics of a long chain polymer molecule in solution with Dirac Delta coupling. An exact analytical perspective.

In this article, we present an exact analytically solvable two state model for calculating the rate of reversible looping of a long chain polymer molecule in solution. In our two state model, one of the two states represent an open chain polymer molecule and the other state represents a closed chain.. One can quantitatively measure the kinetic parameters such as the rate constants, the long term rate constant and the average term rate constant of the reaction from macroscopic measurements like the length of the polymer, the bond length and the relaxation time. The dynamics of the end-to-end distance of both open chain and the closed chain polymer are represented by a Smoluchowski-like equation for a single particle doing random walk under the realm of two different harmonic potentials. The coupling between these two potentials are assumed to be a Dirac Delta function in our model. We have also incorporated the effect of all other chemical reactions involving at least one end of the open chain polymer molecule on the rate of end-to-end loop formation. The closed chain polymer molecule can be converted to an open-chain molecule by breaking any bond - the effect of these reactions on the rate of end-to-end loop formation as well as the rate involving one of the ends are also considered in our model.

Conformational transitions of poly(ethylene oxide) in supersonic jets of supercritical CO2

The supersonic gas jets are proposed as a tool for researching conformational transitions of polymer chain molecules in untraditional (supercritical) fluids. The working fluid of the jet and the solvent for polymers in this case are supercritical fluids. This method is used for the microencapsulation of TiO2 nanoparticles in poly(ethylene oxide) (Mv = 8,000,000). The suspension of TiO2 nanoparticles in the polymer solution in supercritical carbon dioxide is expanded into vacuum or background gas. The substrate of the jet resulting from rapid expansion was investigated by SEM. Along the axis of the jet, zones of coil-globule-coil transitions were found. The position and extent of these zones can be controlled by varying the conditions in the reactor (pressure, temperature, co-solvent concentration) and background gas pressure in the nozzle chamber.

Thermal Pyrolysis of Polypropylene Plastic Waste into Liquid Fuel: Reactor Performance Evaluation

The amount of plastic waste is growing over years due to the vast applications of plastics in many sectors. Of the various processes that can be used to convert solid waste into fuels, the pyrolysis process has been identified as having significant potential. Pyrolysis thermally degrading long chain polymer molecules into smaller, less complex molecules, through heat and pressure with little or in absence of oxygen. In this study, a 125 dm3 pyrolysis reactor was designed and its performance was evaluated. The feedstock for the reactor was 1 kg polypropylene type of plastic waste and conducted at temperature of 250 °C, 300 °C, 350 °C and 400 °C, each process was carried out at 30 minutes and 60 minutes of operating time. The results showed that at a temperature of 400 °C, for a period of 60 minutes, a maximum yield of 88.86% liquid fuel was achieved. Obtained pyrolysis liquid fuel is comparable with the commercial fuel set by Indonesian Ministry of Energy and Mineral Resources. Furthermore, the viscosity and calorific value of liquid fuel produced are close to those of kerosene, meanwhile the density is close to the density of gasoline.

Universal Scaling of Phase Diagrams of Polymer Solutions

A combination of microfluidic and small-angle laser light scattering enables us to map phase diagram of two polymers with different chain lengths in three solvents in an unprecedented speed. Each precisely measured phase diagram leads to a pair of critical temperature (Tc) and volume fraction of polymer (ϕc), in which ϕc is scaled to the chain length (N) as ϕc ∼ N–0.37±0.01. Accounting for a huge size difference of polymer chain and solvent molecules, an adjustable volume ratio (Rc) of solvent to polymer is introduced to generate a dimensionless reduced volume fraction ψ {= ϕ/[ϕ + Rc(1 – ϕ)]}, so that each skewed phase diagram is shifted and symmetrized with a symmetrical axis ψc = 0.325 ± 0.002. After normalized by a solvent and polymer (not chain length) dependent constant ψ0, all of the measured 17 phase diagrams collapsed into one master curve, |ψ – ψc|/ψ0 = e0.325±0.007N0.152±0.004, where e = |T – Tc|/Tc, a reduced temperature. As N → ∞, |ψ – ψc| ∼ |ϕ – ϕc|/ϕc nearby the critical point so that our re...

Abrasive flow finishing of FDM printed parts using a sustainable media

PurposeThe purpose of this paper is to study the integration between fused deposition modeling (FDM) technology and abrasive flow machining process to improve the surface quality of FDM printed parts. FDM process has some limitations in terms of accuracy and surface finish. Hence, post-processing operations are essential to increase the quality of the part.Design/methodology/approachInitially, a sustainable polymer abrasive gel-based media (SPAGM) using natural polymer and natural additives (waste vegetable oil) was prepared using different combinations of (abrasive mesh size, percentage of abrasives and percentage of liquid synthesizer); then the characterization of media was done to check various properties. As media is an essential part in the process which helps in increase the surface finish, it needs to have some desired characteristics such as the following: the developed SPAG needs to hold the abrasives; its viscosity has to be medium so that it can easily flow through the machine; and its thermal stability caused by the increase in the temperature during various cycles of operation. For that, it is characterized rheologically as well as thermally to find its various properties.FindingsExperiments were performed on FDM-printed parts using an L9 orthogonal array with different parameters to find their effect on the workpiece. Scanning electron microscope images of SGAPM showed sharp edges of abrasive particles and bonding pattern between polymer chain molecules. Good surface finish and material removal rate (MRR) was observed at high pressure and long finishing time with 50 per cent abrasive concentration.Originality/valueThe authors confirm that this work is original and has neither been published elsewhere nor is it currently under consideration for publication elsewhere.

Controllable Conformation Transfer of Conjugated Polymer toward High Photoelectrical Performance: The Role of Solvent in Induced-Crystallization Route

In the present work, polyimides with different conformation (dendritic, spherulitic, and laminar) were synthesized in different solvents. The strong solvent-dependent conformation variation is found intimately related to the specific interactions between the polymer chain and solvent molecules that have a primary driving force for the chain diffusion and rearrangement. Moreover, the photoelectrical properties of polyimide were sensitively influenced by the crystal structure and polymer morphology. In laminar conformation with strong intermolecular π–π interactions, the light absorption as well as the mobility and separation of photoinduced carriers were greatly improved compared with similar values of dendritic and spherulitic ones. For photocatalytic hydrogen evolution from water splitting, polyimide with laminar conformation exhibits 16 times enhancement in activity than the dendritic. This work provides further insight into the intrinsic interacting mechanism of solvent-induced crystallization of conju...

Die Symmetrie von Spiralketten

In crystals, polymeric chain molecules often adopt helical structures. Neglecting small distortions possibly caused by an anisotropic environment within the crystal, the symmetry of the single helix can be described by a rod group, which has translational symmetry in one dimension. The rod groups have Hermann-Mauguin symbols similar to space groups, beginning with a script style \scr p followed by a screw-axis symbol; the order of the screw axis can adopt any value. In a crystal, the rod-site symmetry, the so-called penetration rod group, must be a common crystallographic rod subgroup of the molecular rod group and the space group. Instructions are given for the derivation of the rod subgroups in question for a molecular helical rod group of any order. In polymer chemistry, a helix is designated by a (chemical) symbol like 7/2, which means 7 repeating units in 2 coil turns of covalent bonds per translational period. The corresponding Hermann-Mauguin screw-axis symbol is easily derived with a simple formula from this chemical symbol; for a 7/2 helix it is 73 or 74, depending on chirality. However, it is not possible to deduce the chemical symbol from the Hermann-Mauguin symbol, because it depends on where the covalent bonds are assumed to exist. Covalent bonds are irrelevant for symmetry considerations; a symmetry symbol does not depend on them. A chemically right-handed helix can have a left-handed screw axis. The derivation of the Hermann-Mauguin symbol of a multiple helix is not that easy, as it depends on the mutual position of the interlocked helices; conversion formulae for simpler cases are presented. Instead of covalent bonds, other kinds of linking can serve to define the chemical helix, for example, edge- or face-sharing coordination polyhedra.

Pronounced Dielectric and Hydration/Dehydration Behaviors of Monopolar Poly(N-alkylglycine)s in Aqueous Solution.

Poly(N-methylglycine) (NMGn) and poly(N-ethylglycine) (NEGn) obtained by polymerization reactions initiated by benzylamine have no carboxy termini, such as those in normal polyamides, but have only amino termini, which exist primarily as cations in aqueous media at a pH value of ca. 9.5, observed in aqueous solutions without any buffer reagents. Therefore, polypeptoids, such as NMGn and NEGn, possessing a degree of polymerization (DP) higher than a certain value behave as cationic monopolar polymeric chain molecules in aqueous solution. It has not been clarified so far whether such a monopolar chain molecule exhibits dielectric relaxation (DR) behavior resulting from its molecular motions in aqueous media as dipolar chain molecules. DR measurements revealed that NMG19 and NEG17, possessing DPs of 19 and 17, respectively, dissolved in pure water clearly demonstrated pronounced DR behavior caused by fluctuating molecular motions of cationic termini at relaxation times of ca. 4 and 9 ns at 10 °C (283 K). The hydration numbers of NMG19 and NEG17 per monomeric residue (nm) in aqueous solution were also evaluated via DR data as functions of temperature, and the nm value of ca. 4.5 at 10 °C showed a remarkable reduction to ca. 2.0 around 40 °C (313 K) and 30 °C (303 K), depending on differences in the substituted group: methyl and ethyl groups. This temperature-dependent hydration/dehydration behavior found in NMG19 and NEG17 slightly influenced the sizes and molecular dynamics of the monopolar chain molecules in aqueous solution.

Laboratory Study Displacement Efficiency of Viscoelastic Surfactant Solution in Enhanced Oil Recovery

Polymer/surfactant combination solutions were easy to suffer chromatographic separation effect when injected into a relatively low permeability reservoir for the poor injection ability. In addition, the long chain polymer molecules are easy to be cracked when passing through the porous media with low pore throat radius. These problems limit the polymer/surfactant combination flooding used in the poor reservoirs for enhanced oil recovery (EOR). The conventional viscoelastic surfactant (VES) is mainly used in fracturing or drilling. In this paper, we present a novel viscoelastic surfactant, VES-JS, which is designed for EOR. It has a unique ability that allows it to have viscoelasticity like the polymer solution and the capacity to deduce the interfacial tension (IFT) value of oil and water to order 10–2 ∼ 10–3mN/m. For the self-assemble ability, it can reform network structure when it stiff in the porous media. Under the reservoir condition, 65 °C, 100 × 10–3 μm2, VES-JS shows good viscoelasticity and ultr...

Initial stage of stress relaxation in oriented polymers

The initial stage of stress relaxation, i.e., a decrease of the stress with time in an extended solid at a fixed length of the specimen, has been studied in oriented fibers of a linear polymer, polypropylene, chosen as the object of investigation. Experimental data have been obtained, and the stress in the object from the beginning of tensile loading of the specimen has been analyzed. It has been found that the stress relaxation caused by thermal fluctuation conformational transitions in stretched chain polymer molecules occurs from the beginning of the stretching of the polymer fiber. The time dependence of the stress relaxation of polypropylene fibers in all initial stages of deformation of the fibers has been elucidated.