The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform

Masaru Matsuo - One of the best experts on this subject based on the ideXlab platform.

  • Molecular-weight dependence of morphology and mechanical properties of ultrahigh-molecular-weight polyethylene gel films
    Polymer, 1991
    Co-Authors: Tetsuya Ogita, Nobuyasu Suzuki, Fumihiko Ozaki, Ryo Yamamoto, Masaru Matsuo
    Abstract:

    Abstract Films of three kinds of ultrahigh-molecular-weight polyethylenes (UHMWPE) with molecular weights of 6 × 106, 3 × 106 and 1 × 106 were produced by gelation/crystallization from dilute solutions. The dried gel films were stretched up to their maximum draw ratios. The molecular-weight dependences of morphology and mechanical properties of the drawn films have been examined using wide-angle X-ray diffraction, small-angle X-ray scattering, birefringence, crystallinity and Stress Relaxation Modulus. It turned out that the long period, molecular orientation and crystallinity were hardly affected by molecular weight, while the Stress Relaxation Modulus was strongly affected. The master curves indicated that the decrease in the Stress Relaxation Modulus was more pronounced as the molecular weight of the test specimens decreased. This was thought to be due to a drastic increase of the slippage of molecular chains, leading to the disappearance of tie molecules and/or entanglement meshes under the external applied Stress.

  • Molecular-weight dependence of morphology and mechanical properties of ultrahigh-molecular-weight polyethylene gel films
    Polymer, 1991
    Co-Authors: Tetsuya Ogita, Nobuyasu Suzuki, Fumihiko Ozaki, Ryo Yamamoto, Masaru Matsuo
    Abstract:

    Abstract Films of three kinds of ultrahigh-molecular-weight polyethylenes (UHMWPE) with molecular weights of 6 × 106, 3 × 106 and 1 × 106 were produced by gelation/crystallization from dilute solutions. The dried gel films were stretched up to their maximum draw ratios. The molecular-weight dependences of morphology and mechanical properties of the drawn films have been examined using wide-angle X-ray diffraction, small-angle X-ray scattering, birefringence, crystallinity and Stress Relaxation Modulus. It turned out that the long period, molecular orientation and crystallinity were hardly affected by molecular weight, while the Stress Relaxation Modulus was strongly affected. The master curves indicated that the decrease in the Stress Relaxation Modulus was more pronounced as the molecular weight of the test specimens decreased. This was thought to be due to a drastic increase of the slippage of molecular chains, leading to the disappearance of tie molecules and/or entanglement meshes under the external applied Stress.

Joerg Baschnagel - One of the best experts on this subject based on the ideXlab platform.

  • shear Modulus and shear Stress fluctuations in polymer glasses
    Physical Review Letters, 2017
    Co-Authors: I. Kriuchevskyi, J. P. Wittmer, Hendrik Meyer, Joerg Baschnagel
    Abstract:

    Using molecular dynamics simulation of a standard coarse-grained polymer glass model, we investigate by means of the Stress-fluctuation formalism the shear Modulus μ as a function of temperature T and sampling time Δt. While the ensemble-averaged Modulus μ(T) is found to decrease continuously for all Δt sampled, its standard deviation δμ(T) is nonmonotonic, with a striking peak at the glass transition. Confirming the effective time-translational invariance of our systems, μ(Δt) can be understood using a weighted integral over the shear-Stress Relaxation Modulus G(t). While the crossover of μ(T) gets sharper with an increasing Δt, the peak of δμ(T) becomes more singular. It is thus elusive to predict the Modulus of a single configuration at the glass transition.

  • Numerical determination of shear Stress Relaxation Modulus of polymer glasses.
    European Physical Journal E, 2017
    Co-Authors: I. Kriuchevskyi, J. P. Wittmer, O. Benzerara, Hendrik Meyer, Joerg Baschnagel
    Abstract:

    Focusing on simulated polymer glasses well below the glass transition, we confirm the validity and the efficiency of the recently proposed simple-average expression $G(t) = \mu_{A}- h(t)$ for the computational determination of the shear Stress Relaxation Modulus G(t). Here, $\mu_{A}= G(0)$ characterizes the affine shear transformation of the system at t = 0 and h(t) the mean-square displacement of the instantaneous shear Stress as a function of time t. This relation is seen to be particulary useful for systems with quenched or sluggish transient shear Stresses which necessarily arise below the glass transition. The commonly accepted relation $ G(t)=c(t)$ using the shear Stress auto-correlation function c(t) becomes incorrect in this limit.

  • Numerical determination of shear Stress Relaxation Modulus of polymer glasses.
    The European physical journal. E Soft matter, 2017
    Co-Authors: I. Kriuchevskyi, J. P. Wittmer, O. Benzerara, Hendrik Meyer, Joerg Baschnagel
    Abstract:

    Focusing on simulated polymer glasses well below the glass transition, we confirm the validity and the efficiency of the recently proposed simple-average expression [Formula: see text] for the computational determination of the shear Stress Relaxation Modulus G(t). Here, [Formula: see text] characterizes the affine shear transformation of the system at t = 0 and h(t) the mean-square displacement of the instantaneous shear Stress as a function of time t. This relation is seen to be particulary useful for systems with quenched or sluggish transient shear Stresses which necessarily arise below the glass transition. The commonly accepted relation [Formula: see text] using the shear Stress auto-correlation function c(t) becomes incorrect in this limit.

  • Marginally compact hyperbranched polymer trees.
    Soft matter, 2017
    Co-Authors: Maxim Dolgushev, J. P. Wittmer, O. Benzerara, Hendrik Meyer, Albert Johner, Joerg Baschnagel
    Abstract:

    Assuming Gaussian chain statistics along the chain contour, we generate by means of a proper fractal generator hyperbranched polymer trees which are marginally compact. Static and dynamical properties, such as the radial intrachain pair density distribution ρpair(r) or the shear-Stress Relaxation Modulus G(t), are investigated theoretically and by means of computer simulations. We emphasize that albeit the self-contact density diverges logarithmically with the total mass N, this effect becomes rapidly irrelevant with increasing spacer length S. In addition to this it is seen that the standard Rouse analysis must necessarily become inappropriate for compact objects for which the Relaxation time τp of mode p must scale as τp ∼ (N/p)5/3 rather than the usual square power law for linear chains.

  • Simple average expression for shear-Stress Relaxation Modulus.
    Physical Review E, 2016
    Co-Authors: J. P. Wittmer, Joerg Baschnagel
    Abstract:

    Focusing on isotropic elastic networks we propose a simple-average expression G(t) = mu(A) - h(t) for the computational determination of the shear-Stress Relaxation Modulus G(t) of a classical elastic solid or fluid. Here, mu(A) = G(0) characterizes the shear transformation of the system at t = 0 and h(t) the (rescaled) mean-square displacement of the instantaneous shear Stress (tau) over cap (t) as a function of time t. We discuss sampling time and ensemble effects and emphasize possible pitfalls of alternative expressions using the shear-Stress autocorrelation function. We argue finally that our key relation may be readily adapted for more general linear response functions.

Christopher M. Stafford - One of the best experts on this subject based on the ideXlab platform.

  • Quantifying the Stress Relaxation Modulus of polymer thin films via thermal wrinkling.
    ACS Applied Materials & Interfaces, 2010
    Co-Authors: Edwin P. Chan, Santanu Kundu, Qinghuang Lin, Christopher M. Stafford
    Abstract:

    The viscoelastic properties of polymer thin films can have a significant impact on the performance in many small-scale devices. In this work, we use a phenomenon based on a thermally induced instability, termed thermal wrinkling, to measure viscoelastic properties of polystyrene films as a function of geometric confinement via changes in film thickness. With application of the appropriate buckling mechanics model for incompressible and geometrically confined films, we estimate the Stress-Relaxation Modulus of polystyrene films by measuring the time-evolved wrinkle wavelength at fixed annealing temperatures. Specifically, we use time−temperature superposition to shift the Stress Relaxation curves and generate a Modulus master curve for polystyrene films investigated here. On the basis of this master curve, we are able to identify the rubbery plateau, terminal Relaxation time, and viscous flow region as a function of annealing time and temperatures that are well-above its glass transition. Our measurement t...

  • Quantifying the Stress Relaxation Modulus of polymer thin films via thermal wrinkling.
    ACS applied materials & interfaces, 2010
    Co-Authors: Edwin P. Chan, Santanu Kundu, Qinghuang Lin, Christopher M. Stafford
    Abstract:

    The viscoelastic properties of polymer thin films can have a significant impact on the performance in many small-scale devices. In this work, we use a phenomenon based on a thermally induced instab...

Tetsuya Ogita - One of the best experts on this subject based on the ideXlab platform.

  • Molecular-weight dependence of morphology and mechanical properties of ultrahigh-molecular-weight polyethylene gel films
    Polymer, 1991
    Co-Authors: Tetsuya Ogita, Nobuyasu Suzuki, Fumihiko Ozaki, Ryo Yamamoto, Masaru Matsuo
    Abstract:

    Abstract Films of three kinds of ultrahigh-molecular-weight polyethylenes (UHMWPE) with molecular weights of 6 × 106, 3 × 106 and 1 × 106 were produced by gelation/crystallization from dilute solutions. The dried gel films were stretched up to their maximum draw ratios. The molecular-weight dependences of morphology and mechanical properties of the drawn films have been examined using wide-angle X-ray diffraction, small-angle X-ray scattering, birefringence, crystallinity and Stress Relaxation Modulus. It turned out that the long period, molecular orientation and crystallinity were hardly affected by molecular weight, while the Stress Relaxation Modulus was strongly affected. The master curves indicated that the decrease in the Stress Relaxation Modulus was more pronounced as the molecular weight of the test specimens decreased. This was thought to be due to a drastic increase of the slippage of molecular chains, leading to the disappearance of tie molecules and/or entanglement meshes under the external applied Stress.

  • Molecular-weight dependence of morphology and mechanical properties of ultrahigh-molecular-weight polyethylene gel films
    Polymer, 1991
    Co-Authors: Tetsuya Ogita, Nobuyasu Suzuki, Fumihiko Ozaki, Ryo Yamamoto, Masaru Matsuo
    Abstract:

    Abstract Films of three kinds of ultrahigh-molecular-weight polyethylenes (UHMWPE) with molecular weights of 6 × 106, 3 × 106 and 1 × 106 were produced by gelation/crystallization from dilute solutions. The dried gel films were stretched up to their maximum draw ratios. The molecular-weight dependences of morphology and mechanical properties of the drawn films have been examined using wide-angle X-ray diffraction, small-angle X-ray scattering, birefringence, crystallinity and Stress Relaxation Modulus. It turned out that the long period, molecular orientation and crystallinity were hardly affected by molecular weight, while the Stress Relaxation Modulus was strongly affected. The master curves indicated that the decrease in the Stress Relaxation Modulus was more pronounced as the molecular weight of the test specimens decreased. This was thought to be due to a drastic increase of the slippage of molecular chains, leading to the disappearance of tie molecules and/or entanglement meshes under the external applied Stress.

J. P. Wittmer - One of the best experts on this subject based on the ideXlab platform.

  • shear Modulus and shear Stress fluctuations in polymer glasses
    Physical Review Letters, 2017
    Co-Authors: I. Kriuchevskyi, J. P. Wittmer, Hendrik Meyer, Joerg Baschnagel
    Abstract:

    Using molecular dynamics simulation of a standard coarse-grained polymer glass model, we investigate by means of the Stress-fluctuation formalism the shear Modulus μ as a function of temperature T and sampling time Δt. While the ensemble-averaged Modulus μ(T) is found to decrease continuously for all Δt sampled, its standard deviation δμ(T) is nonmonotonic, with a striking peak at the glass transition. Confirming the effective time-translational invariance of our systems, μ(Δt) can be understood using a weighted integral over the shear-Stress Relaxation Modulus G(t). While the crossover of μ(T) gets sharper with an increasing Δt, the peak of δμ(T) becomes more singular. It is thus elusive to predict the Modulus of a single configuration at the glass transition.

  • Numerical determination of shear Stress Relaxation Modulus of polymer glasses.
    European Physical Journal E, 2017
    Co-Authors: I. Kriuchevskyi, J. P. Wittmer, O. Benzerara, Hendrik Meyer, Joerg Baschnagel
    Abstract:

    Focusing on simulated polymer glasses well below the glass transition, we confirm the validity and the efficiency of the recently proposed simple-average expression $G(t) = \mu_{A}- h(t)$ for the computational determination of the shear Stress Relaxation Modulus G(t). Here, $\mu_{A}= G(0)$ characterizes the affine shear transformation of the system at t = 0 and h(t) the mean-square displacement of the instantaneous shear Stress as a function of time t. This relation is seen to be particulary useful for systems with quenched or sluggish transient shear Stresses which necessarily arise below the glass transition. The commonly accepted relation $ G(t)=c(t)$ using the shear Stress auto-correlation function c(t) becomes incorrect in this limit.

  • Numerical determination of shear Stress Relaxation Modulus of polymer glasses.
    The European physical journal. E Soft matter, 2017
    Co-Authors: I. Kriuchevskyi, J. P. Wittmer, O. Benzerara, Hendrik Meyer, Joerg Baschnagel
    Abstract:

    Focusing on simulated polymer glasses well below the glass transition, we confirm the validity and the efficiency of the recently proposed simple-average expression [Formula: see text] for the computational determination of the shear Stress Relaxation Modulus G(t). Here, [Formula: see text] characterizes the affine shear transformation of the system at t = 0 and h(t) the mean-square displacement of the instantaneous shear Stress as a function of time t. This relation is seen to be particulary useful for systems with quenched or sluggish transient shear Stresses which necessarily arise below the glass transition. The commonly accepted relation [Formula: see text] using the shear Stress auto-correlation function c(t) becomes incorrect in this limit.

  • Marginally compact hyperbranched polymer trees.
    Soft matter, 2017
    Co-Authors: Maxim Dolgushev, J. P. Wittmer, O. Benzerara, Hendrik Meyer, Albert Johner, Joerg Baschnagel
    Abstract:

    Assuming Gaussian chain statistics along the chain contour, we generate by means of a proper fractal generator hyperbranched polymer trees which are marginally compact. Static and dynamical properties, such as the radial intrachain pair density distribution ρpair(r) or the shear-Stress Relaxation Modulus G(t), are investigated theoretically and by means of computer simulations. We emphasize that albeit the self-contact density diverges logarithmically with the total mass N, this effect becomes rapidly irrelevant with increasing spacer length S. In addition to this it is seen that the standard Rouse analysis must necessarily become inappropriate for compact objects for which the Relaxation time τp of mode p must scale as τp ∼ (N/p)5/3 rather than the usual square power law for linear chains.

  • Simple average expression for shear-Stress Relaxation Modulus.
    Physical Review E, 2016
    Co-Authors: J. P. Wittmer, Joerg Baschnagel
    Abstract:

    Focusing on isotropic elastic networks we propose a simple-average expression G(t) = mu(A) - h(t) for the computational determination of the shear-Stress Relaxation Modulus G(t) of a classical elastic solid or fluid. Here, mu(A) = G(0) characterizes the shear transformation of the system at t = 0 and h(t) the (rescaled) mean-square displacement of the instantaneous shear Stress (tau) over cap (t) as a function of time t. We discuss sampling time and ensemble effects and emphasize possible pitfalls of alternative expressions using the shear-Stress autocorrelation function. We argue finally that our key relation may be readily adapted for more general linear response functions.