ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    ISSN: 1435-1528
    Keywords: Internalstress ; physicalageing ; amorphous phase ; stressrelaxation ; polyethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The stress relaxation behavior of high density polyethylene (HDPE) can be affected by ageing processes; e.g., with increasing storage time at a low temperature following a quench from a high temperature (close to the melting point) the relaxation curves change shape. More specifically, the stress level approached after very long loading times in a stress relaxation experiment increases with the ageing time. Here this stress level is denoted “the internal stress”σ i. Struik has pointed out that physical ageing may also occur in semicrystalline polymers like HDPE. The physical ageing should then be associated with that part of the amorphous phase which is closest to the surfaces of the crystallites. This part of the amorphous phase of HDPE can be assumed to have a restricted mobility at room temperature and may have a partially “glassy” character. In this paper a model for explaining the increase inσ i for HDPE with increasing ageing time is proposed and discussed. It is based on the separation of the amorphous phase into two parts as suggested by Struik. The glassy part of the amorphous phase ages in a way similar to that of an entirely amorphous polymer quenched to a temperature below its glass transition, while the more rubbery phase is assumed not to undergo any physical ageing.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    ISSN: 1435-1528
    Keywords: Viscoelastic properties ; internalstress ; coupling agentHDPE ; glass sphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract It is shown that covalent bonding between high density polyethylene (HDPE) and glass spheres can have a significant influence on the stress relaxation behaviour and the creep properties of the corresponding composites at room temperature. The bonding is obtained by reacting the glass spheres with an azide functional alkoxysilane which is capable of bonding to the HDPE-chain. The internal stress, evaluated from relaxation experiments, increased markedly as a result of this treatment, and it is suggested that the internal stress level reflects the properties of the interphase region between the filler and the bulk matrix and its effect on the viscoelastic properties.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Rheologica acta 27 (1988), S. 273-278 
    ISSN: 1435-1528
    Keywords: Composite ; silane coupling agent ; interface ; maleic anhydride-modifiedrubber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Dynamic mechanical spectra of various composites of high density polyethylene (PE), ethylene propylene diene rubber (EPDM), and calcium carbonate were obtained at 190°C with a parallel plate instrument. Interfacial effects were found to have a significant influence on the dynamic mechanical behavior of these composites. Composites of calcium carbonate in PE displayed prominent particle—particle interaction effects. This resulted in a greatly enhanced dynamic shear modulusG d due to the filler addition. Treatment of the calcium carbonate with gamma-aminopropyltriethoxysilane (γ-APS) or gamma-methacryloxypropyltrimethoxysilane (γ-MPS) significantly reduced the particle—particle interactions. Solution deposition of EPDM or EPDM grafted with maleic anhydride (EPDM-MA) on the calcium carbonate, before incorporation into a PE composite, also had a significant effect on the composite properties. Comparison of data from composites treated with EPDM vs. EPDM-MA suggested the presence of an interaction between the calcium carbonate surface and the maleic anhydride modification. This conclusion was further supported by solid state proton NMR relaxation model experiments which showed significant immobilization of the EPDM-MA chains on the filler surface. The treatment of calcium carbonate withγ-APS orγ-MPS before incorporation into multicomponent polyethylene-rubber-filler composites also had a significant influence on the dynamic mechanical properties of the resultant composites. There is evidence for a reaction betweenγ-APS and EPDM-MA during processing on the roll mill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 29 (1994), S. 2350-2358 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    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 The structure and properties of polypropylene (PP) and ethylene propylene copolymer (EPR) blends filled with BaSO4 have been investigated. The aspect of structure control concerned was the separate dispersion of filler and rubber in the PP matrix or encapsulation of the filler in the rubber phase. The former structure prevails in the PP/EPR/BaSO4 systems, and addition of maleic anhydride-grafted polypropylene (MAPP) enhances the adhesion between the PP matrix and the filler. Encapsulation of the filler particles into the elastomer takes place when maleated EPR-rubber (EPMA) is used, and the encapsulated structure prevails even under the severe shearing conditions of injection molding. The improved matrix/filler adhesion resulted in increased yield stress and tensile strength, but decreased impact resistance. The particle size of the filler proved to be a crucial factor; below a certain particle size aggregation becomes a dominating factor. Extensive aggregation leads to the deterioration of all mechanical properties, especially to decreased impact strength.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 670-678 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 dynamic shear viscosity and the morphology of polypropylene homopolymer and copolymer blended with linear low density polyethylene are studied. A maximum in the dynamic shear viscosity vs. blend composition is reported for the polypropylene copolymer, linear low density polyethylene system. The increasing dynamic shear viscosity is in accordance with the occurrence of a morphology of polyethylene inclusions in rubber surrounded by a polypropylene matrix. Comparing calculations of the dynamic shear viscosities - based on a shell model with interlayer - and experimental results supports this view.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 423-430 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copolyamides of nylon-4,6 and nylon-4,T were prepared by a two-step method: (1) a prepolymerization in an autoclave (40 min at 210°C) and (2) a postcondensation in the solid state (4 h, 260°C). On these materials was studied the melting behavior with DSC, the crystalline structure with WAXS, the water absorption, and the mechanical properties with a torsion pendulum. In these copolyamides the order was found to remain high, but the crystalline structures of -4,6 and -4,T were not isomorphous. The torsion moduli increased with -4,T content both at RT and at 140°C.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 211 (1996), S. 269-275 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Positron annihilation lifetime spectroscopy was used to study the time dependence of the ortho-positronium lifetime and intensity and the ortho-positronium lifetime distribution in a poly(ethylene oxide)/poly(methyl methacrylate) blend after heat treatment. The recently introduced maximum entropy for lifetime analysis (MELT) program and the POSITRONFIT program were used for evaluation of the spectra. The blend shows a large excess in free volume hole size shortly after cooling from the melt. Withi time, the hole size decreases, while the orthio-positronium intensity remains constant. The lifetime distribution width does njot vary systematically with time. Differential scanning calorimetry measurements show that crystallisation of the poly(ethylene oxide) phase occurs parallel to the decrease in ortho-positronium lifetime.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 351-356 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 temperature dependence of the interfacial dielectric loss process in glass bead-filled high density polyethylene (HDPE) due to an interfacially adsorbed water layer has been studied. The frequency of maximum dielectric loss shifts to lower frequencies with decreasing temperature. This is thought to be due to decreasing mobility of the free charge carriers in the adsorbed water layer, resulting in the reduced conductivity of the layer. The shifting of the loss peaks with temperature can be described with the well-known Arrhenius relation. The energy of activation, as obtained from this relation, shows a stron dependence on the thickness of the adsorbed layer. For thinner layers a higher activation energy is found, indicating that the charge carriers are increasingly affected by the presence of a layer of bound charges on the glass surface. This thickness dependence of the activation energy offers some possible applications. First, information on the water layer thickness can be extracted from the energy of activation, and second, it becomes possible to study the effect of interfacial modifications such as the application of coupling agents.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...