2 edition of influence of pressure on relaxations in glassy state polymers found in the catalog.
influence of pressure on relaxations in glassy state polymers
H. G. Moneypenny
Written in English
Thesis(Ph.D.) - Loughborough University of Technology 1976.
|Statement||by H.G. Moneypenny.|
Three amorphous polymers, polymethyl methacrylate, polystyrene and polycarbonate were tested in uniaxial tension, uniaxial compression, plane strain compression and simple shear, over a range of temperatures. In each test, the yield point was precisely determined via residual strain measurements after unloading. With the yield stresses determined for these four different stress Cited by: Dielectric relaxation spectroscopy was used to investigate the molecular dynamics of model segmented polyurethane copolymers having identical hard segments and hard segment weight fractions, but with four different soft segment chemistries of particular interest in biomedical devices. All soft segments have molecular weight ∼ g/mol and are composed of either tetramethylene oxide Cited by:
Part of the Advances in Polymer Science book series (POLYMER, volume ) Abstract Analysis of the crystallization kinetics of numerous polymers has revealed a bimodal dependence of the gross crystallization rate on temperature, often leading to the occurrence of two crystallization-rate maxima at widely different by: The physical properties of the glass depend on the procedure used to produce the glass. In particular, if the glass is obtained through the variation of external thermodynamic parameters, the specific way in which the parameters are varied (thermodynamic history) has influence on the final properties. In this work, we studied the effect of thermodynamic history on secondary relaxation inside Cited by: 5.
Glass-Transition Phenomena in Polymer Blends Ioannis M. Kalogeras University of Athens, Faculty of Physics, Department of Solid State Physics, Zografos , Greece Introduction The ever-increasing demand for polymeric materials with designed multi-functional properties has led to a multiplicity of manufacturing approaches andFile Size: 6MB. The Johari-Goldstein secondary (β) relaxations are an intrinsic feature of supercooled liquids and glasses. They are crucial to many properties of glassy materials, but the underlying mechanisms are still not established. In a model metallic glass, we study the atomic rearrangements by molecular dynamics simulations at time scales of up to by:
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Influence of stress state and temperature on secondary relaxations in polymeric glasses* B. Read Division of Materials Applications, National Physical Laboratory, Teddington, Middlesex, TW11 OL W, UK (Received 11 February 1 ; revised 3 April 1 ) Using a range of dynamic techniques, the components of the complex tensile modulus E*, Poisson's ratio u*, shear modulus G* and bulk Cited by: Glass-forming high polymers have been densified by application of high hydrostatic pressure (≈ kbar) in the melt, followed by cooling under pressure to ambient.
A density increase of about 1% was induced in each of the following polymers: polyvinyl chloride, polymethyl methacrylate, polystyrene, polychlorostyrene, polychlorostyrene, polymethoxystyrene and : Henry G.
Moneypenny. The dielectric β relaxation of polyvinyl chloride has been studied in the ranges of temperature, pressure and frequency, to K, 1 × 10 5 to 3 × 10 8 N m –2 and 1 to 10 5 Hz. Detailed results are discussed in terms of current concepts of the α, β and (αβ) relaxations which occur in amorphous polymers and in small molecule glass forming systems.
On the basis of the dynamics of hole motion, a unified physical picture has emerged which enables us to discuss the structure relaxation, physical aging, and glassy state deformation.
The links between the bulk and shear relaxations, the change in deformation from linear to nonlinear viscoelastic responses, and the nonlinear viscoelastic nature Cited by: 8.
This study presents the kinetic sorption behavior of six different gases (CO2, C3H8, C3H6, Xe, Kr, and Ar) in films of the glassy polyimide Matrimid using a magnetic suspension balance. The dynamic mass uptake was analyzed using a model discriminating and quantifying separate contributions of Fickian diffusion and relaxations.
The model provides a quantitative insight into the pressure Cited by: A unified account of the structural relaxation and nonlinear deformation in glassy polymers is presented.
The glassy state relaxation is derived from the local configurational rearrangements of. Part of the Advances in Polymer Science book series (POLYMER, volume 46) Abstract Although secondary relaxations (dispersions, transitions) in glassy polymers have extensively been studied within the last two decades, current understanding of their molecular mechanisms still remains incomplete and by: The temperature dependence of the apparent activation energy for polymer relaxations might be explained in part by the temperature dependence of the thermal expansion coefficient and the.
Influence of pressure on fast picosecond relaxation in glass-forming materials Article (PDF Available) in Physical Review B 81(10) January with Reads How we measure 'reads'.
MODEL FOR EXPLICIT SEPARATION OF DIFFUSION AND RELAXATION PARAMETERS The sorption process in glassy polymers is considered here as the linear superposition of phenomenologically indepen- dent contributions from Fickian diffusion and polymeric by: Distinct segmental α and local glassy state β relaxations are clearly evidenced in the PUU – data, as shown in Fig.
5b, whereas a very broad (α 1 + α 2) process for PU is observed, in keeping with previous experimental findings [21,30,31]. Both segmental α relaxations are associated with the soft segments in the soft phases Cited by: 4. The transformation of the metastable supercooled liquid or the equilibrium melt to the glassy state is usually achieved by cooling (see Glass Transition), though there are other routes such as the application of hydrostatic pressure (see Glass Formation in Polymers: Introduction).
The temperature dependence of the apparent activation energy for polymer relaxations is signif icantly different above and below the cr ossover temperature typical of eac h relaxation.
(8) Correlation between mechanical strength of glassy polymers and secondary, glassy state relaxations. (9) The need to prepare highly crystalline polymers in the completely amorphous state.
The heat capacities, thermal expansivities, and isothermal compressibilities of polystyrene and a mixture of o-terphenyl (67%) and o-phenylphenol (33%) (abbreviated as OTP−OPP) were measured around their glass transition temperatures at atmospheric pressure and high pressure ( MPa for polystyrene and MPa for OTP−OPP).
The measurements were performed simultaneously with a novel Cited by: In an attempt to clarify the criteria satisfied at the glass transition (T g) the effect of pressure on T g of polyvinyl acetate has been measured by dielectric and volumetric tric constant and loss has been measured as a function of temperature (25–°C.), pressure (0– atm.) and frequency (–10 kcycles/sec.).
The merging of the main and the secondary dielectric relaxations in a series of six polymers has been investigated by using broadband dielectric spectroscopy (− Hz). The data have been analyzed in two different ways.
In one case, the whole relaxation process has been modeled by the simple addition of the relaxation functions corresponding to the main and secondary by: Temperature Modulated Calorimetry of Glassy Polymers and Polymer Blends.
Macromolecules31 (3), DOI: /mat. Johari and, G. Sartor. Hydrogen-Bond Equilibrium and the Enthalpy and Entropy Relaxations in a Nonpolar State of Vitrified by: Kwang-Sup Lee, Paras N. Prasad, in Comprehensive Polymer Science and Supplements, Blends of Glassy Polymers and Dye Molecules.
Since glassy polymers are in an amorphous state, they often show high optical quality and good physical properties. Therefore, these polymers are promising as matrices for NLO dyes (type A in Figure 2).
Singer et al. 13 found SHG in a polymer. Content: The structure and properties of glassy polymers: an overview / Anita J. Hill and Martin R. Tant --The use of configurational entropy to derive the kinetic properties of polymer glasses / Edmund A. Di Marzio --Entropy, landscapes, and fragility in liquids and polymers, and the [delta]Cp [excess heat capacity] problem / C.A.
Angell --Dynamic properties of polymer melts above the glass. The amorphous part behaves much like super cooled liquid in this segment. The overall physical behaviour of the polymer in this intermediate segment is much like a rubber.
Below [math]T_g[/math]: The polymer material viewed as a glass is hard and rigid, showing a specified coefficient of thermal expansion. The glass is closer to a crystalline solid than to a liquid in.
The pressure dependencedT g /dP of glass transition temperatureT g has received considerable interest due to its connection with solid state thermodynamic properties and theories of glass transition. Free volume considerations (1, 2) led to an estimate of the pressure effect onT g, showing thatdT g /dP had to depend on thermal expansion and compressibility changes atT g through Cited by: 7.In twenty-nine chapters by leading authorities, Structure and Properties of Glassy Polymers provides readers with comprehensive coverage of basic and applied research on glass polymers as well as a wealth of information on current topics such as molecular modeling, characterization, polymer glasses in confined spaces, and conducting glass polymers.