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  • Semi-Crystalline Polymers  (1)
  • bismaleimide composite  (1)
  • heat transfer  (1)
  • magnetic coating  (1)
  • micro-thermal analysis  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 54 (1998), S. 501-519 
    ISSN: 1572-8943
    Schlagwort(e): complex heat capacity ; heat transfer ; phase lag ; TMDSC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In the present study, a complete model of thermal diffusion in a TMDSC specimen is presented. The governing equation takes into account thermal conductivity and does not neglect temperature gradients. This model is solved analytically for a specimen of cylindrical geometry with two surfaces following the block temperature and considering the third surface insulated. The full analytical solution consists of a transient and an asymptotic expression. The asymptotic expression is divided into an underlying and a cyclic part to allow comparison with existing models. The present model finds that the phase angle between the temperatures of sample and block are dependent upon the sample material, which has not been predicted by existing models. Moreover, the present model does not require the use of an experimentally determined constant as long as the cell is ideal. It was found that the phase lag between sample and block temperatures could be described by two effective thermal diffusivities, Λ′ and Λ″, instead of complex heat capacities $$c'_p {\text{ and }}c''_{\text{p}} $$ and $$c'_p {\text{ and }}c''_{\text{p}} $$ . These heat capacity parameters were viewed as mathematical artifacts arising from the use of an over-simplified governing equation that does not take into account thermal conductivity and thermal gradients within the specimen.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 599-608 
    ISSN: 1572-8943
    Schlagwort(e): microscale heat transfer ; micro-thermal analysis ; thermosetting polymers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Glass transitions of amorphous polystyrenes with low polydispersity were evaluated using the modulated Local Thermal Analysis mode of the TA Instruments 2990 µ TA and evaluating the thermomechanical signal. Transition temperature variance and fraction of transitions measured were compared for high molecular mass thermosetting materials and the melt of Nylon 6.6. The transition reproducibility was found to decrease as the molecular size of the polymer samples increased. Reproducibility also decreased for thermosetting materials when the experimental ramp rate was decreased. Heat transfer within the specimen was evaluated using finite element analysis, allowing scaling of microscale experimental results for comparison to bulk transitions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1435-1536
    Schlagwort(e): Semi-Crystalline Polymers ; orientation ; crystallinity ; magnetic coating ; processing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract A combination of structure identifying and bulk property experiments were combined with a two-phase analytical methodology to elucidate the influence of a magnetic tape coating process on the substrate polymer film. Employing a typical tape manufacturing process that utilizes coating, drying, and calendering stages, polyethylenete-rephthalate polymer film samples with and without the magnetic coating were prepared. Experiments and modeling studies performed on these samples demonstrate that the drying and calendering processes may increase the crystallinity and noncrystalline orientation of the substrate film. In addition, dynamic mechanical experiments identified a viscoelastic transition at 50 °C for the PET substrate film sample which is near the glass transition of the magnetic coating utilized. Overall, the results of this investigation provide a basis for evaluating structure property interrelations of polymer-based magnetic tapes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1019-1027 
    ISSN: 0887-6266
    Schlagwort(e): bismaleimide composite ; thermogravimetry ; anistropic degradation ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The weight loss of carbon fiber-reinforced polymeric composites in air has been found to depend on the sample surface characteristics such as fiber orientation with respect to the exposed surfaces. This phenomenon can be attributed to the diffusion of oxygen through the sample and the dependence of diffusion rate on fiber orientation. Recently, an anisotropic degradation methodolgy was proposed, based on the unreactedcore principle, commonly used in catalysis, as extended to account for the anisotropic effects. In this work, these anisotropic diffusion effects were also identified for small thermogravimetric (TGA) samples. Isothermal TGA experiments were performed in air at 310°C using samples weighing 10-163mg. Weight loss was found to be a strong function of fiber orientation. The anisotropic degradation methodology successfully predicted the weight loss of all samples, although some deviation attributed to the sample edge effects was observed. When samples were examined by optical microscopy, a degraded zone was observed on the sample surfaces. The thickness of this layer depended on the type of exposed surface, validating the anisotropic degradation methodology. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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