Shrinkage sample

Fig. 5.58 Effeet of drying and earbonation on shrinkage. Sample curing ...

The DMA can be operated in a dynamic or static mode. In the dynamic mode, a probe with an oscillating frequency enables the entire photoinduced polymerization to be followed with real-time monitoring of shrinkage, sample viscosity, and modulus. Alternatively, if it is operated in a static mode, the DMA essentially becomes a TMA. The dynamic-mode DMA measurements are possible but difficult to carry out since the probe must essentially float on the initially uncured liquid and hence, is not discussed here. Instead, TMA-like measurements in a static mode are described, as illustrated in Rg. 4.32. Bair et al. (1998,2000). This static-mode technique can be applied to samples with a wide range of shrinkages, from <0.1% to >10%. The detection limit for sample shrinkage in 500-pm-thick specimens using this static DMA method is... 

The oil and gas samples are taken from the appropriate flowlines of the same separator, whose pressure, temperature and flowrate must be carefully recorded to allow the recombination ratios to be calculated. In addition the pressure and temperature of the stock tank must be recorded to be able to later calculate the shrinkage of oil from the point at which it is sampled and the stock tank. The oil and gas samples are sent separately to the laboratory where they are recombined before PVT analysis is performed. A quality check on the sampling technique is that the bubble point of the recombined sample at the temperature of the separator from which the samples were taken should be equal to the separator pressure. 

Characterization of the samples by TGA and CHN analysis shows that the template was effectively removed (C < 0.2 wt%). Small-angle X-ray scattering data of the calcined solid shows a reduction in the unit cell due to thermal shrinkage, while the values for the Fenton samples coincide with the starting precursor. Our approach therefore completely preserves the unit cell corresponding to the diameter of the micelles contained in the mesophase. 

The range of semi-dilute network solutions is characterised by (1) polymer-polymer interactions which lead to a coil shrinkage (2) each blob acts as individual unit with both hydrodynamic and excluded volume effects and (3) for blobs in the same chain all interactions are screened out (the word blob denotes the portion of chain between two entanglements points). In this concentration range the flow characteristics and therefore also the relaxation time behaviour are not solely governed by the molar mass of the sample and its concentration, but also by the thermodynamic quality of the solvent. This leads to a shift factor, hm°d, is a function of the molar mass, concentration and solvent power. 

An increase of the light-intensity leads not only to a faster cure but also to a more complete polymerization 19. For instance, the amount of residual unsaturation of the UV-cured acrylate polymer was shown to drop from 15 to 5% when the light intensity was increased from to 3 to 100 mW cm-2. This trend can be explained by two factors (i), an increase of the sample temperature which provides more molecular mobility and (ii), a longer time lag between conversion and shrinkage... 

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