Cooling of the polymer jet in fibre spinning

Conclusions The effect of various technological parameters (jet stretch ratio, temperature and flow rate of the polymer melt, temperature and velocity of the air which cools the melt, and rheological characteristics of the polymer) on the change in temperature and viscosity of the polymer jet along the length of the spinning zone has been investigated.It has been shown that the temperature of the cooling air, the Stanton number, and the velocity of the cooling air exert the greatest effect on the fibre temperature at the take-up device, but jet stretch ratio and rheological properties of the melt affect fibre temperature only slightly.Translated from Khimicheskie Volokna, No. 6, pp. 19–20, November–December, 1987.     

Three‐dimensional trajectory of electrospun polymer solution jet using digital holographic microscopy

The three‐dimensional trajectories of polymer solution jets during the electrospinning of polymer nanofibers were experimentally investigated. Test conditions included water solutions of polyethylene oxide (PEO) with concentrations typical of those producing beaded nanofibers, driving voltages ranging from 5 kV to 15 kV to generate a single polymer jet and injection pressures ranging from 0 kPa to 55 kPa. The present holographic imaging setup resolved the spatial growth of the bending instabilities, which is beneficial for validating numerical models. The results also showed the bead formation on the polymer fiber in‐flight. POLYM. ENG. SCI., 54:1765–1773, 2014. © 2013 Society of Plastics Engineers     

Comparative measurements of interfacial tension in a model polymer blend

This work shows the application of several experimental methods to the measurement of the interfacial tension, σ, between two immiscible polymers. A quantitative knowledge of the interfacial tension is important in view of the crucial role that this parameter plays in polymer blend processing. Common to all methods presented here are two main points. The first is that σ is obtained from experiments where the shape of the interface between the liquids is directly observed by means of optical microscopy techniques. The second point is that the interface geometry is controlled by a balance between the interfacial force and the viscous stresses generated by some flow applied to the system. Measurements have been carried out on a model polymer blend, whose constituents are a poly-isobutylene and a poly-dimethylsiloxane. both transparent and liquid at room temperature. When compared with each other, the values of interfacial tension obtained from the different methods show a good quantitative agreement. Excellent agreement is also found with results for the same system previously published in the literature.     

Surface tension of polymer liquids

A cell theory for the prediction of the surface tension of simple liquids is adapted to polymer liquids. The combinatory, free volume and potential energy zero terms of the partition function are all modified to account for the preservation of connectivity when a surface is created. Theory and experiment are in good agreement without an adjustable surface parameter.     

Retracted: Electrospinning instabilities in the drop formation and jet ejection at various concentrations of polyvinyl alcohol polymer solution

This article has been retracted because of prior acceptance by another publication. The publisher regrets any inconvenience this may have caused.     

Stability to the process of spinning a jet of polyacrylonitrile solution in dimethylformamide

Conclusions An experimental study of stretching resonance in spinning solutions of polyacrylonitrile in dimethylformamide has been performed, and conditions for stable spinning of these solutions has been determined.It has been shown that the mathematical model used to describe theoretically spinning process stability adequately describes this process only on the condition that the rheological characteristics are functions of lengthwise deformation rate and spinning conditions.Translated from Khimicheskie Volokna, No. 4, pp. 16–18, July–August, 1988.     

Dynamic interfacial tension between a thermotropic liquid‐crystalline polymer and a flexible polymer

When a short fiber of a thermotropic liquid‐crystalline polymer retracts in a quiescent, flexible polymer matrix, the polydomain texture inside the fiber evolves simultaneously. We have demonstrated experimentally that the two processes are coupled. The dynamic interfacial tension, determined from the retraction of the short fiber, decreases with time. On the other hand, we have determined the aspect ratio of the polydomains inside the fiber through the power spectra of two‐dimensional discrete Fourier transformations of polarized optical microscopy images. The polydomains are initially elongated and aligned with the fiber axis. As the fiber retracts into a spherical drop, the polydomains first retract into a circular shape and then are squeezed into elongated shapes perpendicular to the original fiber axis. An exponential function correlates the evolution of the dynamic interfacial tension with that of the aspect ratio of the textures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3114–3120, 2006     

A suspension of spheres in a dilute polymer solution

The Hookean dumbbell model of a macromolecule predicts non‐uniform density and pressure fields surrounding a sphere buoyant in a dilute polymer solution when the size of the sphere is of the same order of magnitude as the size of the macromolecules. Using this prediction, the root mean square separation distance of a suspension of spheres buoyant within a dilute polymer solution is found to be inversely proportional to both the square of the radius of a sphere and the density of the polymer solution. The phase space distribution function for an ensemble of spheres immersed at equilibrium within a dilute polymer solution is found and used to define the magnitude of the ensemble average peculiar acceleration of the spheres. The peculiar acceleration results from changes in direction of the peculiar velocity. It is found to be directly proportional to the temperature, polymer density, and square of the radius of a sphere and inversely proportional to the mass of a sphere. The self‐ diffusivity of the particles varies directly with the square root of the temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Phase transition in a polymer chain in dilute solution

Some general theoretical arguments are advanced to help in an understanding of the behaviour of a single molecular chain with intramolecular forces of van der Waals type. Analogy with a fluid suggests that as N→∞ a first-order phase transition takes place at a unique condensation temperature and this defines a unique ?-temperature. However, for finite N the transition becomes rounded and hence the ?-temperature is dependent on N. Instead of a ?-temperature one should now talk of a ?-region, an idea already put forward by Mazur et al. from an analysis of Monte Carlo data. Evidence for this pattern of behaviour is adduced from a lattice model of a self-avoiding walk with near-neighbour attractive forces using ideas which have proved useful in critical phenomena. Attention is drawn to a ferroelectric model which shows some similarities in behaviour.     

Structural and dynamic heterogeneity in a telechelic polymer solution

We utilize molecular dynamics simulations to investigate the implications of micelle formation on structural relaxation and polymer bead displacement dynamics in a model telechelic polymer solution. The transient structural heterogeneity associated with incipient micelle formation is found to lead to a ‘caging’ of the telechelic chain end-groups within dynamic clusters on times shorter than the structural relaxation time governing the cluster (micelle) lifetime. This dynamical regime is followed by ordinary diffusion on spatial scales larger than the inter-micelle separation at long times. As with associating polymers, glass-forming liquids and other complex heterogeneous fluids, the structural τ_s relaxation time increases sharply upon a lowering temperature T, but the usual measures of dynamic heterogeneity in glass-forming liquids (non-Gaussian parameter α₂(t), product of diffusion coefficient D and shear viscosity η, non-Arrhenius T-dependence of τ_s) all indicate a return to homogeneity at low T that is not normally observed in simulations of these other complex fluids. The greatest increase in dynamic heterogeneity is found on a length scale that lies intermediate to the micellar radius of gyration and intermicellar spacing. We suggest that the limited size of the clusters that form in our (low concentration) system limit the relaxation time growth and thus allows the fluid to remain in equilibrium at low T.     

Dynamic interfacial tension in melts of fibre-forming polymer blends

The dynamic interfacial tension was determined in melts of fibre-forming polymer blends: PPr-HDPE, PPr-LDPE, P4MP1-HDPE, P4MP1-PPr, PCA-PPr, PCA-HDPE, PCA-LDPE. It was determined by the method of capillary decomposition of liquid polymer jets. Translated from Khimicheskie Volokna, No. 1, pp. 19–22, January–February, 1998.     

Isothermal stretching of the jet of polymer melt in aerodynamic fibre spinning

Conclusions Equations have been obtained for determining the diameter of a polymer melt jet over the length of the isothermal section, which is the zone of spinning fibre by the aerodynamic method.A comparison of the results of calculations with experimental data shows that they agree satisfactorily.Translated from Khimicheskie Volokna, No. 2, pp. 18–19, March–April, 1988.     

Interaction of mass exchange and jet tension in spinning of nitron fibres

The reciprocal effect of mass exchange and tension of spun Nitron fibre in the spinning bath was demonstrated. The concentration region of the concentration of solvent in the spinning bath which guarantees attaining high elasticity and a strength of 100 cN/tex and the more finished fibre with a linear density of 0.01 tex was established.Nitron Plant, Novoiazot Industrial Association, Uzbekistan; Mogilev Institute of Technology, Belarus'. Translated from Khimicheskie Volokna, No. 6, pp. 41–43, November–December, 1993.     

The falling laminar jet of semi-dilute polymer solutions

The studies of falling laminar jets have been done mainly on Newtonian jet due to the complexity of non-Newtonian fluid parameter. Numerical solutions of the Newtonian jet equation are in good agreement with the experimental results of polymer solutions in the experimental concentration range. Numerical simulation results suggest that the free falling jet is mostly influenced by the Froude number. The jet radius increases with the Froude number. It was found that surface tension or viscosity does not contribute much to the shapes of the free falling jet.     

Surface and interfacial tension of polymer liquids –a review

The surface tension of a polymer liquid is a property of considerable practical importance. Within the past decade the experimental difficulties in accurately measuring the surface tension of viscous polymer melts have been overcome, and a considerable body of data is now available. This review discusses the measurement techniques which have proved useful, the results which have been obtained, and theoretical approaches which have been applied to them. A tabulation of surface and interfacial tension values which have been published up to mid-1971 is included.