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Showing 1 to 20 of 41 for “"Physical Aging"”.
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Physical Aging of Miscible Polymer Blends
Physical aging measurements were performed on various polymeric glasses with the overriding goal of developing a better molecular picture of the nonequilibrium glassy state. To this end, aging-induced changes in mechanical properties and in the thermodynamic state (volume and enthalpy) were …
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Physical Aging, Solubility, and Water Activity of Selected Disaccharides
… flows in MDSC slightly increased with longer aging times and the Tg calculated for SDSC decreased whereas Tg calculated for MDSC slightly increased with aging time. In experiment two, maltose glasses aged at the $\rm Tg - 20\sp\circ C$ took longer to approach equilibrium. The excess enthalpy …
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Molecular Simulation Studies of Physical Aging and Rejuvenation in Polymer Glasses
… the metabasins. Finally, we show that the aging dynamics in polymer glass are related to the transition between the metabasins, and these transitions occur less as the system evolves toward the low energy regions on the potential energy landscape with increasing barrier height between …
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Physical Aging and Characterization of Engineering Thermoplastics and Thermoplastic Modified Epoxies
In this work the relationship between physical properties, such as physical aging and relaxation time distributions, and chemical structure for a variety of polymeric systems were investigated. Although there is a vast amount of physical aging data for polymers, most of these studies do not attempt …
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The effect of physical aging on the inelastic deformation of glassy polymers
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991.
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Crystallization, Melting Behavior, Physical Properties, and Physical Aging of Ethylene/1-Octene Copolymers
The time dependence of the physical properties of ethylene/1-octene (EO)-copolymers after primary crystallization is investigated by calorimetry, density, and creep measurements. The temporal evolution of the multiple melting of EO-copolymers is monitored by differential scanning calorimetry. The …
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The effect of physical aging on the creep response of a thermoplastic composite
The effect of thermoreversible physical aging on the linear viscoelastic creep properties of a thermoplastic composite was investigated. Radel X/IM7, an amorphous composite material considered for use in the next generation high speed transport aircraft, was studied. The operating environment for …
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Phenomenological Study of Enthalpy Relaxation and Physical Aging of Glucose, Fructose and Their Mixture
… x and beta with the thermal history (i.e., aging time, aging temperature and cooling-heating rates indicated the failure of the original assumption of the models for the sugar systems."
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Gas transport properties in polycarbonate - Influence of the cooling rate, physical aging, and orientation
… were examined as a function of the cooling rate, physical aging, and orientation. Such conditions affect the free volume content and its size and shape distribution. Results obtained from permeation experiments were accompanied with dynamic mechanical and density measurements. The experimental …
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The effects of molecular orientation on the physical aging behavior of oriented glassy amorphous polymers
… orientation has an effect on the rate of physical aging in amorphous glassy polymers. There is already a large body of literature concerning the phenomenon of physical aging, although the vast majority has been directed toward isotropic, unoriented systems. The importance of this study is …
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Structure-property relations in liquid crystalline and thermoplastic polymers: Crystal structure and morphology of liquid crystalline polyethers and the interaction of creep and physical aging in a semicrystalline thermoplastic matrix composite
The crystal structure and morphology of a family of aromatic-aliphatic azomethine polyethers (where the aliphatic unit was composed of CH$\sb2$ units ranging in length from n = 1, 4, 7, 8, 9 and 10) has been examined primarily by Electron microscopy(EM) and Electron diffraction(ED).
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Infrared Study of the Nonequilibrium Glassy State of Polymers (Frequency Shifts)
… nature of polymer glasses induces a physical aging process which results in time dependent changes in physical, mechanical and thermodynamic properties. Valence coordinate deformation (VCD) is proposed as an intramolecular stress associated with the vitrification and aging process. …
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The effect of environmental aging/exposure on the durability of high performance polymeric composites
… materials have been known to undergo both physical as well as chemical aging. The aging time, temperature, and environment play a significant role in affecting the physical and chemical aging behavior in the polymers. Currently, there is a dearth of information on the combined effects of …
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Time Dependent Properties of Semicrystalline Poly(Arylene Ether Ether Ketone) (Peek) Above and Below the Glass Transition
… of several time dependent phenomena - "physical aging", "secondary crystallization", "multiple melting" of lamellae with different thermal stability etc. Their interrelation - common origin and kinetics of development, is characterized extensively for the first time in this study. The …
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The accelerated characterization of viscoelastic composite materials
… to testing. A closely related phenomenon of physical aging is described. The effect of each on the glass transition temperature and strength is discussed. Creep rupture results are provided for a variety of geometries and temperatures for T300/934 graphite/epoxy. The results are found to …
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Time, temperature and frequency viscoelastic behavior of commercial polymers
… with emphasis on characterizing the effects of physical aging, temperature, and frequency. The procedure for finding the shift rate, mu, is based on Struik's protocol. Time-temperature superposition (TTSP) of short-term data, at different temperatures, was done. Effective Time Theory (ETT) is …
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Comparison of conventional and super-glassy polymers
… polymeric membranes show a strong tendency to physical aging and plasticization, which lead to changes in their performance with time. Up to know, it is not fully understood how these drawbacks are connected to the internal molecular mobility. In this study, a commonly used non-porous polyimide …
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Aging model for commercial polymers
Physical aging of polyvinyl chloride, high-density polyethylene, and polyester reinforced with polyester fibers specimens have been investigated. These materials are commercially available and are currently used in trenchless relining of sewer pipes. The analysis uses the effective-time theory and …
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Chemical and physical stability of spray-dried and glass encapsulated spray-dried flavors stored below their glass transition temperatures
… to: 1) compare and contrast the chemical and physical stability of SD and two MET flavors, 2) compare the chemical and physical stability at all storage temperatures (Ts) and times, 3) determine possible mechanisms of flavor loss, such as volatile permeation and/or oxidative degradation, and …
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