Bulk measurements, thermomechanical

The microstructures of the consolidated and deformed samples were characterized by X-ray diffraction, optical and electron microscopy (SEM and TEM). The samples for mechanical testing have been prepared by spark erosion. The linear thermal expansion was determined by using a thermomechanical system (TMA). The temperature-dependent elastic moduli have been measured by the resonance frequency and the pulse-echo method. The bulk moduli were determined by synchrotron radiation diffraction using a high-pressure diamond-die cell at HASYLAB. The compression and creep tests were performed with computer-controlled tensile testing and creep machines. 

Two examples of the use of localised thermal analysis are provided in order to illustrate the generic applications of this approach. Figure 8 shows localised thermomechanical analysis of the surface of the multi-layer film in Figure 4. Measurements were made at points within this image describing the bulk polymer, the central gas-barrier layer and the thin tie-layer between this and the bulk film. The melting transition temperatures are consistent with high density polyethylene, poly(ethylene-co-vinyl alcohol) and medium density polyethylene for the bulk, gas barrier and tie layers, respectively [101],... 

The second, obvious application is studying polvmer-filler interactions in filled and reinforced composites. Some data are presented for wollastonite and quartz filled Bisphenol-A based and cycloaliphatic epoxies [6]. These data show, that Tg shifts observed by different relaxation methods (dielectric spectroscopy, DSC, thermomechanical measurements) are not necessarily the same (Table 1.), they depend on the effective frequency, changes in activation energy have also to be taken into account. Correlations between Tg shift and polymer adsorption can be understood using Lipatov s theory [7]. Positive Tg shift usually indicates strong adhesion, while negative Tg shift can be explained by the fact that the adsorbed polymer layer forms a looser structure than that of the bulk material. If both the neat resins and their composites are studied dielectrically, the origin of the low-... 

Three carbon fibre-reinforced polyimides were exposed to UV radiation at 177C, at three different intensities for three different times, so that the product of intensity and time was a constant. Intensities of 1,2 and 3 suns, where one sun is the power in space at one earth-sun distance, were used, for a time periods of 500, 250 and 167 h. The samples were characterised by X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, thermomechanical analysis and dynamic mechanical analysis. Measurement of bulk properties showed no difference between samples exposed to heat and UV radiation, and control samples. Surface analysis by XPS showed an apparent decrease in carbonyl concentration on the surface of some exposed samples. This was correlated to surface contamination by a silicone-containing material. 3 refs. 

In a series of our studies, the presence of the microphase-separated structure in PAS film is effectively estimated from the EPMA measurement [10], the thermomechanical properties [14], the gas permeabilities [14] of PAS, and cell adhesion onto a PAS surface [15]. In addition, the results of the XPS and contact angle measurements suggest that PDMS components fully cover the outermost surface of the PAS film [10]. The appearance of the periodicity of the microphase-separated structures of PAS film, however, are still unclear. In this section, to clarify the bulk and surface structures visually, we observed the appearance of the microdomains of the bulk and that near the surface for the multiblock copolymer by means of transmission electron microscopy (TEM). 

PAS-8 were greater than those on SILASTIC 500-1, PAS-41, and 71. Although the surfaces of PASs and SILASTIC 500-1 were hydrophobic, the contact angle for PAS-8 was slightly lower than those for SILASTIC 500-1, PAS-41, and 71 (see Table 9). It was thought that the PAS-8 surface might have an influence on the aramid block. The phenomenon of the cell adhesion onto PAS-41 and 71 could not be explained by hydrophobicity alone. In former sections, the results of the gas-permeability measurement and the dynamic thermomechanical analysis of PAS implied the presence of a microphase-separated structure between PDMS and aramid phases in the PASs containing over 26 wt% of PDMS [14]. Moreover, a TEM study indicated that PAS films possessed microdomain structures in their bulk phases. That is, not only the hydrophobicity of the surfaces, but also the presence of a microphase-separated structure in the PASs may influence cell adhesion. 

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