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  • 1
    Electronic Resource
    Electronic Resource
    Free-volume distribution and positronium formation in amorphous polymers: Temperature and positron-irradiation-time dependence (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4654-4661 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Positron annihilation lifetime spectroscopy was used to study the free-volume size distribution and the o-Ps (ortho-positronium) formation in two amorphous polymers. We performed positron lifetime measurements on poly(vinyl acetate) (PVAc) in the temperature range of 84–414 K and on poly(methyl methacrylate) (PMMA) in the temperature range of 84–454 K and as a function of time (〈200 h) at four temperatures (T=84, 149, 224, and 249 K). The glass transition temperature Tg and secondary transition temperature were determined from the average o-Ps lifetime τ3 versus temperature. The width of the o-Ps lifetime distribution was evaluated using the maximum entropy method (MELT). Analysis by the MELT program on the spectra shows that (i) the standard deviation σ(τ3) of the o-Ps lifetime distribution in PVAc and PMMA increases slightly with temperature in the glassy state, and then increases significantly with temperature above the glass transition temperature Tg; (ii) the σ(τ3) in PMMA has no observable variation as a function of positron irradiation time, which suggests that the measured free-volume distribution is not influenced by the positron irradiation. The o-Ps formation probability shows large variations with temperature, thermal history, and measuring time. These effects are discussed in the framework of the spur model. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475876
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  • 2
    Electronic Resource
    Electronic Resource
    Interfacial interaction in kaolin-filled polyethylene composites (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 624-630 
    Details
    ISSN: 1435-1536
    Keywords: Polyethylene ; kaolin filler ; torsion pendulum ; fracture ; heat of fusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Kaolin-filled polyethylene composites were prepared under different mixing conditions. Viscoelastic properties of specimens were measured by torsion pendulum tests. Fracture behaviour was studied by tensile tests, and fracture surfaces by scanning electron microscopy and ESCA. Fracture properties turned out to be strongly influenced by processing conditions and to correlate with the amount of undissolvable polyethylene bound to the filler surface. This bound layer has an appreciably lower heat of fusion than the unfilled polyethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01419886
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  • 3
    Electronic Resource
    Electronic Resource
    An interlayer model for the complex dielectric constant of composites (1990)
    Springer
    Colloid & polymer science 268 (1990), S. 315-325 
    Details
    ISSN: 1435-1536
    Keywords: Interlayermodel ; dielectricconstant ; composite ; filledpolymer ; interfacial ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The complex dielectric constant of a composite with an interlayer was studied as a function of the volume fractions and the properties of the filler, the interlayer, and the matrix. The theoretical approach is analogous to the calculation of the shear modulus, the bulk modulus, and the termal expansivity of particulate filled polymers using the interlayer model (IM). An analytical expression describing the influence of an interlayer on the generalized dielectric constant of the composite as a function of the volume fraction and interlayer properties is derived. In the case of a composite with non-conductive constituents, the equations for static and oscillatory electric fields are similar. When conductive constituents are present, the complex dielectric constants have to be replaced by the generalized complex dielectric constants. For a composite of non-conductive materials, without interlayer, the obtained relation reduces to the classical Rayleigh equation. In the case of a composite with conductive constituents, also without interlayer, the complete solution of Wagner's theory is found. Special attention has been paid to the case of a water interlayer in a glass-bead filled non-conductive matrix material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411674
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  • 4
    Electronic Resource
    Electronic Resource
    Interfacial effects on the ageing behavior of high density polyethylene filled with glass spheres (1988)
    Springer
    Colloid & polymer science 266 (1988), S. 990-998 
    Details
    ISSN: 1435-1536
    Keywords: Ageing ; fillers ; polyethylene ; surface-treatment ; silane layers ; viscoelastic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The stress relaxation and creep behavior of unfilled high density polyethylene (HDPE) and HDPE filled with untreated and surface-treated glass spheres were measured at room temperature. A silane-based coupling agent capable of providing a covalent bond between HDPE and the glass spheres was used for the surface-treatment. Two different amounts of the coupling agent were employed giving silane layers on the fillers with different thicknesses. The effect of ageing time at room temperature on the viscoelastic properties after quenching from 100 °C to room temperature in ice water was also investigated. The effects of the surface treatment of the fillers and the ageing time was characterized by means of the internal stress (σ i ) concept. Theσ i -value increased with the degree of interaction of the filler/matrix interface and the ageing time. It was here not possible to superimpose the different flow curves with regard to the ageing time with sufficient accuracy. This is due to the variation ofσ i with ageing time. The surface-treatment of the filler had a marked effect on the creep behavior at high applied stress levels and on the ageing behavior of the composites, presumably due to the formation of an interphase region close to the filler surface with different properties and different ageing characteristics than that of the bulk of the matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01428807
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  • 5
    Electronic Resource
    Electronic Resource
    An interlayer model for the complex dielectric constant of composites: An extension to ellipsoidally shaped particles (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 1069-1079 
    Details
    ISSN: 1435-1536
    Keywords: Interlayer model ; dielectric constant ; composite ; filled polymer ; ellipsoidal particles ; interfacial water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A theoretical interlayer model (IL) has been developed for the complex dielectric constant of a composite in which the filler particles are enveloped with a layer of interfacial material. The filler particles can be of any ellipsoidal shape. Special cases such as spherical particles, needles, and fabrics are shown to be covered by the model. The analytical formula as derived describes the composite properties as a function of the volume fractions of the filler, the layer and the matrix material, their dielectric properties and the filler particle shape factor. In the case of a two-phase composite the model reduces to the well-known Sillars relation for the complex dielectric constant of composite which contains filler particles of ellipsoidal shape. The effect of an interfacial layer on the static dielectric constant of the composite is discussed using the model. Next, the special case of a conductive interfacial layer in an otherwise non-conductive composite is discussed; it illustrates the effect of interfacially adsorbed water on the electrical properties of composites. Some practical examples are shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652870
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal expansivity of particulate composites: Interlayer versus molecular model (1989)
    Springer
    Rheologica acta 28 (1989), S. 302-310 
    Details
    ISSN: 1435-1528
    Keywords: Composite ; thermalexpansivity ; interlayer model ; lattice model ; equation of state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract We continue the comparison of the results of an interlayer model, based on the theory of elastic continua, and a molecular model, derived from a theory of mixtures, previously presented in terms of bulk moduli K. We now derive expressions for the dependence of the thermal expansivityα c on the volume fractionφ f of the filler, at low and elevated values ofφ f . Correspondencies between the characteristic parameters, viz. adhesion and repulsion ratios on the one hand, and interlayer content and thermal properties of matrix, filler, and layer, on the other, are examined. Since in the molecular theory bothα andK are derived from an equation of state, the identical set of parameters determines both functions and suggests correlations between them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01329339
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  • 7
    Electronic Resource
    Electronic Resource
    Generalized stress relaxation behaviour and physical aging in heterogeneous amorphous polyblends (1985)
    Springer
    Rheologica acta 24 (1985), S. 243-249 
    Details
    ISSN: 1435-1528
    Keywords: Stress relaxation ; physical aging ; time-temperature superposition ; time-aging time superposition ; ABS/polycarbonate blend
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The influence of physical aging on viscoelastic behaviour of heterogeneous amorphous polyblends of ABS and polycarbonate was studied by means of stress relaxation experiments at different temperatures. The stress relaxation data of the constituent phases ABS and PC are found to be in agreement with the universal description of relaxation behaviour of amorphous polymers at the onset of the glass-rubber transition. The regimes where master curve construction by time-temperature and time-aging time superposition is permitted could be deduced for the thermorheologically complex polyblends. It is shown that the relaxation curves of the ABS/PC blends can be calculated by means of a quasi-elastic extension of the van der Poel-model using the stress relaxation data of the constituent phases and their volume fractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332603
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  • 8
    Electronic Resource
    Electronic Resource
    Dynamic-mechanical properties of interfacially modified glass sphere filled polyethylene (1988)
    Springer
    Rheologica acta 27 (1988), S. 397-404 
    Details
    ISSN: 1435-1528
    Keywords: Composite ; silane coupling agent ; interface ; Fourier transform infraredspectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Model composites of spherical glass particles dispersed in a matrix of high density polyethylene were prepared both with and without interfacial modification by an azidofunctional trialkoxysilane. Dynamic mechanical measurements of the composites in the melt state were recorded. The unmodified composites behave as theoretically predicted and the effect of particle—particle interaction at high volume fractions can be measured. The composites with a modified interfacial region have greater shear moduli due to the effect of a region surrounding the particle modified by the silane. The material in this region is largely bound to the glass surface and was examined by Fourier transform infrared spectroscopy after extraction of the bulk matrix. Theoretical calculations are shown to be useful in calculating the mechanical properties and volume fraction of the interfacial region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332160
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  • 9
    Electronic Resource
    Electronic Resource
    Bulk modulus of particulate composites: A comparison between a statistical and micro-mechanical approach (1986)
    Springer
    Rheologica acta 25 (1986), S. 161-165 
    Details
    ISSN: 1435-1528
    Keywords: Filled composite ; bulk modulus ; lattice model ; equation of state ; interlayer model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Two models are compared. One is based on the theory of elastic continua, and describes the interaction between filler and matrix in terms of an interfacial layer of varying volume fraction and elastic properties. The other derives from an equation of state for the constituents and the composite, based on molecular considerations. The filler-matrix interaction is then expressed in terms of segmental attractions and repulsions. We examine the dependence of the bulk modulusK c (ϕ f ) on the volume fractionϕ f of filler and then show the correspondence between the two theories in terms of the infinite dilution limit of the ratio [K c (ϕ f ) −K m ]/(K m ϕ f ) where the indexm refers to the matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332134
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  • 10
    Electronic Resource
    Electronic Resource
    Micromechanical deformations in particulate filled thermoplastics: volume strain measurements (1994)
    Springer
    Journal of materials science 29 (1994), S. 2350-2358 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Volume strain measurements were carried out on PP composites containing different CaCO3 fillers. During deformation, a volume increase was detected which could be divided into two linear sections as a function of elongation. Comparison of data with existing theories has shown that in the first part, mostly elastic deformation takes place and the slope can be related to the Poisson's ratio of the composite. Scanning electron microscopy revealed that in the second stage, the dominating micromechanical deformation process is debonding. Void formation is initiated at a certain stress which approximately corresponds to the yield stress of the composites, but data in the literature and model calculations indicate that separation of the matrix/filler interface may start at lower stresses. Initiation stress depends on the particle size of the filler and on interfacial interactions. The rate of volume increase has non-linear dependence on the volume fraction of the filler. Volume strain measurements reflect micromechanical deformations well, but further study is needed to explain contradictions between experimental results and theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00363426
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