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  • Polymer and Materials Science  (16)
  • unfolding models  (3)
  • 11
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 3059-3063 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Four polystyrene-polyurethane mechanical blends were prepared with 5, 10, 20, and 40% thermoplastic polyurethane, respectively. Their impact properties were compared with pure polystyrene and commerical types of impact polystyrene. The rheological properties of the blends were studied with DSC and dynamic mechanical spectroscopy. It was found that addition of softer polyurethane conglomerates embedded inside the polystyrene matrix, although increasing the toughness of the blend as expected from addition of the softer particulate, also increased the glassy region of the blends by shifting their Tgs to higher temperatures. A theory based on the interaction of phases was propounded explaining this phenomenon.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 20 (1976), S. 903-910 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A class of amine-cured epoxy resins containing various amounts of polysulfide plasticizer were subjected to dynamic testing during curing at high temperature. Both E modulus and loss factor were determined simultaneously. It was proved that the method allowed for rapid determination of the general pattern of the crosslinking procedure and the necessary curing time and, in general, that dynamic methods are most suitable for the mechanical characterization of polymers under curing at each stage of the curing cycle.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3019-3025 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The thermomechanical behavior of particle composites was investigated in their transition region. In particular, the value of the glass-transition temperature Tg, which constitutes an upper limit for the structurally important glassy region, was examined. According to experimental evidence existing in the literature the introduction of a reinforcing filler in a polymeric matrix causes Tg of the latter to increase, unless mechanical imperfections counterbalance the reinforcing effect or even produce a Tg for the composite which is lower than that of the matrix. Based on mechanical theories, valid for the mechanical moduli of viscoelastic particle composites, a model was introduced that explains why the glass transition of composite materials may be reduced in some cases, whereas it may be increased in others. The concept of interphase between inclusions and matrix was used for the development of the model. Interphase is assumed to be a region, which is created between the matrix material and the filler particles, both considered as homogeneous and isotropic, whose thermomechanical properties and volume fraction may be determined from the overall thermomechanical behavior of the composite.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 3145-3153 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The influence of moisture absorption on the extent of the boundary interphase in particulate composites is thoroughly studied. It was found that, during the process of moisture absorption there is a variation of the extent of the boundary interphase, closely related to the degradation of the mechanical behavior of the composite, as well as to the percentage amount of moisture absorbed. An explanation of the observed relationship was advanced, based on a theoretical mechanism of absorption. This study complements a previous one, where the observed degradation of the thermomechanical properties of particulate composites due to moisture absorption was shown to be intimately interrelated with the state and extent of the interphase between fillers and matrix.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 2979-2995 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The determination of the cubic thermal expansion coefficient of a two-phase particulate is presented in this paper. The model described is based on the well-known Kerner's model and takes into account the existence of mesophase, which constitutes a boundary layer between inclusions and the matrix in the composite. This layer is assumed as created by the substance of matrix during the preparation procedure of the composite, and it includes areas of imperfections around and near the inclusions. The influence of this layer on the effective properties of the composite has been proved to be significant. In order to take into consideration the influence of mesophase a spherical shell with the average properties of this layer is interposed between the spherical inclusion and the matrix. The evaluation of the average elastic and thermoelastic properties and also of the extent of mesophase is succeeded by considering the two-term unfolding model, introduced previously, for describing the change of the elastic modulus of the mesophase layer of fiber-reinforced and particulate composites. The two-term unfolding model was, in this paper, extended to incorporate the mode of variation of the thermal expansion coefficient and the bulk modulus in the mesophase. The model was applied to a polyurethane rubber filled with particles of sodium chloride, and its predictions were found to be in good agreement with the experimental data.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 3641-3649 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Retardation spectra, derived from dynamic measurements of extension compliances along three decades on the logarithmic scale of frequencies in standard specimens prepared from a fiber-reinforced composite with their fibers parallel to the longitudinal axis of the specimens, have revealed the structure of the matrix material of the composite. The experimental results were used to prove that the physicochemical rearrangements in the vicinity of the inclusions, consisting of restrained development of the macromolecules and especially their side chains due to the presence of the other phase, concentration of voids and dirt, shrinkage stresses developed during curing and creating microcracks (radial as well as along the interface), are activated by the existence of high stress gradients and eventually stress singularities due to the strong adhesion developed between phases.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 32 (1986), S. 6267-6279 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The extent of mesophase, which constitutes the boundary layer between the filler and the matrix of a composite, was defined in this paper along the whole viscoelastic spectrum of the polymeric substance constituting the matrix. The already established two-term unfolding model1-3 was based on thermodynamic measurements of the heat capacity jumps at the glass transition regions of the filled and unfilled substances in order to define the extent of mesophase. In this paper we dispense ourselves with these delicate measurements, based on Lipatov's theory, and we use values taken from the storage and loss compliances of the composite and its constituents, along the whole viscoelastic spectrum of the composite. It was shown that the extent of the mesophase, necessary to sustain the shearing loading between phases, appearing at the glass transition zone, where the loss-compliances presented their characteristic peaks of resonance, remained constant and almost independent of the respective values of mechanical properties at this critical region. It was shown that any set of values of the mechanical characteristic quantities, defining the composite and its constituents along the whole viscoelastic spectrum, is sufficient to evaluate the extent of the mesophase, and this boundary layer undergoes only negligible variations. Experimental evidence with typical E-glass polystyrene and other particulates, at various volume fractions of the filler, yielded a satisfactory coincidence with the results derived by using Lipatov's theory and a constancy of the mesophase thickness along the whole temperature range.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 1493-1503 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The final network structure of epoxy polymers cured with a crosslinking agent is strongly connected with the type and amount of the curing agent and conditions. Concerning the morphology of this network, it has been reported that cured epoxies are two-phase systems, containing roughly spherical floccules arranged in a matrix resembling the constituent phases. In this paper and by using an epoxy-polymer cured with different amounts (i.e., different than the stoichiometric one) of a curing agent, strong indications of their network-structure heterogeneity have been disclosed. For this study, two different experimental techniques, such as dynamic mechanical measurements and DSC tests have been utilised. It was found that cured epoxy-polymers consist of two extreme regions, with low and high crosslink densities, whose volume fractions have been estimated by using a mechanical model applicable for two-phase systems.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 3 (1965), S. 2619-2635 
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The transient extension relaxation modulus E(t) and the lateral contraction ratio vr(t) for a polyurethane elastomer have been simultaneously measured in the transition region from the glassy to the rubbery consistencies of the material. The differential moiré method was used in these measurements and yielded simultaneous values of the longitudinal extension and the lateral contraction principal strains of the tension specimen. Composite curves of E(t) and vr(t) reduced to a standard temperature were obtained by applying the method of reduced variables. The time factors KT in both curves were coincident and they followed the WLF equation. The shear and bulk modulus characteristic functions were determined from the extension modulus and lateral contraction ratio functions. The values of the lateral contraction ratio in relaxation were determined by using data of the extension relaxation modulus along the whole viscoelastic range and the initial value of the lateral contraction ratio at the rubbery state and applying an indirect method. The results obtained by the indirect method coincided with the experimental values. The shear modulus function was evaluated from the extension relaxation modulus and the lateral contraction ratio functions and compared with the shear dynamic compliance determined by Landel. The experimental data indicated that a linear relationship holds between the lateral contraction ratio in relaxation and the bulk modulus along the whole response spectrum. The same relationship was previously shown to hold for a series of various polymeric substances.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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