Samples polymer fibres

We will confine ourselves to those applications concerned with chemical analysis, although the Raman microprobe also enables the stress and strain imposed in a sample to be examined. Externally applied stress-induced changes in intramolecular distances of the lattice structures are reflected in changes in the Raman spectrum, so that the technique may be used, for example, to study the local stresses and strains in polymer fibre and ceramic fibre composite materials. 

The different examples presented in this review show the large range of possible applications of ToF-SIMS in the cultural heritage field. We have seen that it can be used for the characterization of different kinds of materials such as polymers, fibres and textiles, painting materials or biological samples, but any other material could be considered. 

Figure 1.3 present spectra of XLV dye solution absorbtion in the mixture of formic and trifluoro-acetic acids, solutions of dyed fibres before and after spinneret, which are practically laid on each other, showing full solution of the dye and good homogeneization of polymer melt. It should be noted that the samples of fibres, being studied, fully dissolved in solvents without formation of residues (possible products of dye and PCA interaction), which tells about inertia of components regarding each other. Blinding screen was caused mainly by impurities of mechanical nature. 

At this point, we mention a related class of sample, namely oriented samples. In the case of a perfect macroscopic ordering, each equivalent nucleus is oriented identically, and the situation is the same as that in a single crystal. Specific oriented samples of relevance (with varying degrees of ordering) include polymer fibres [4], liquid crystals (LC), [12, 13] and membrane proteins in oriented lipid bilayers [14]. We will return to the latter two cases in the discussion of two-dimensional experiments in Sections 9.5 and 9.6. 

In order to obtain the maximum amount of information about the crystal structure it is necessary to align the crystallites, which can be done by methods described in detail in chapter 10. It is sufficient to note here that suitable orientation is often produced by stretching a fibre of the polymer. In the simplest cases the chain axis of each crystallite, which is designated the c-axis, becomes aligned towards the fibre axis, but there is no preferred orientation of the other two axes around the c-axis. From such a sample a fibre pattern can be obtained, of the type shown in fig. 3.10. 

Gas chromatography, coupled with flame-ionisation, electron capture (for halogenated species) and mass spectrometric detectors, is the most popular tool for determination of SVOCs in melted snow samples [44]. A prerequisite is the efficient separation of the analytes from the aqueous matrix, which can be accomplished using filtration onto quartz fibre filters and sohd phase extraction [88]. Solid phase micro-extraction, which utilises equihbrium-based adsorption of analytes onto a polymer fibre bundle, has also been proposed and tested in laboratory studies [13, 89]. Both methods allow for an efficient transfer into the injection port of a gas chromatograph without water contamination. Directly coupled inlet sampler with GC-EID instrumentation has also been used [90]. The air sample was pre-concentrated using adsorbents (Carbotrap B, Carbosieve), followed by heating and collection on a cryofocuser (a fused silica capillary tube packed with... 

Three phases are involved in headspace extraction, namely the condensed phase, its headspace and the SPME polymer. In the sampling process, the SPME fibre acts as a chemical pump , forcing compounds out of the headspace of a (liquid or) solid phase into a phase-coated fibre. For headspace sampling of volatiles the vapour phase should be in equilibrium with the sample. Sample/air/fibre partitioning of volatiles depends on many factors, including the nature of the sample matrix, presence of interfering compounds, sample and headspace volumes. 

More viscous samples can be subjected to extensional flows when forced through slots or holes. Such flows are relevant to the spinning of polymer fibres, for example nylon threads or spider silk. In the latter case, the spider carries its own spinning machine, called a spinneret, to make its webs. 

Different analytical procedures have been developed for direct atomic spectrometry of solids applicable to inorganic and organic materials in the form of powders, granulate, fibres, foils or sheets. For sample introduction without prior dissolution, a sample can also be suspended in a suitable solvent. Slurry techniques have not been used in relation to polymer/additive analysis. The required amount of sample taken for analysis typically ranges from 0.1 to 10 mg for analyte concentrations in the ppm and ppb range. In direct solid sampling method development, the mass of sample to be used is determined by the sensitivity of the available analytical lines. Physical methods are direct and relative instrumental methods, subjected to matrix-dependent physical and nonspectral interferences. Standard reference samples may be used to compensate for systematic errors. The minimum difficulties cause INAA, SNMS, XRF (for thin samples), TXRF and PIXE. 

Application to solid polymer/additive formulations is restricted, for obvious reasons. SS-ETV-ICP-MS (cup-in-tube) has been used for the simultaneous determination of four elements (Co, Mn, P and Ti) with very different furnace characteristics in mg-size PET samples [413]. The results were compared to ICP-AES (after sample dissolution) and XRF. Table 8.66 shows the very good agreement between the various analytical approaches. The advantage of directly introducing the solid sample in an ETV device is also clearly shown by the fact that the detection limit is even better than that reported for ICP-HRMS. The technique also enables speciation of Sb in PET, and the determination of various sulfur species in aramide fibres. ETV offers some advantages over the well-established specific sulfur analysers very low sample consumption the possibility of using an aqueous standard for calibration and the flexibility to carry out the determination of other analytes. The method cannot be considered as very economic. 

The heat flow into (endothermic) or out (exothermic) of a sample as a function of temperature and time is measured using the technique of DSC. In particular, it is used to study and determine the temperature of thermal transitions. For polymers, these include Tg, the glass transition temperature, Tc, the (exothermic) temperature of crystallisation for polymers that can crystallise, and Tm, the (endothermic) melting temperature. A DSC measurement requires only a small amount of sample 2-20 mg of a film, powder, fibre or liquid samples can be analysed in a DSC pan. 

Polymer materials are frequently used matrices for the indicator chemistry in optical sensors. This is necessary for several reasons first, the indicator has to be immobilized to an optical waveguide or an optical fibre which is then brought into contact with the analyte solution. If one would pour an aqueous solution of the indicator dye directly into the sample solution, e.g. into a bioreactor, then the whole sample solution would be contaminated. 

The SPME process, adapted for solid or viscous matrix, is shown in Figure 10.1. A fused silica fibre, coated with a polymer, is installed inside a stainless steel hollow needle. In the first step, the needle is introduced in the sample vial through the septum. The fibre is then exposed to the headspace above the sample and the organic analytes adsorb to the coating of the fibre. After a variable sampling time, the fibre is drawn into the needle and the needle is withdrawn from the sample vial. Finally, in the same way, the fibre is introduced into the chromatograph injector where the analytes are thermally desorbed. 

Table 2 Results of the calculated effect of the low molecular weight fraction on the ultimate fibre strength for the three PpPTA polymer samples listed in Table 1. The constants used in the calculation are ec=240,g=2, t0=0.4 GPa and u0= 1.3 nm.The maximum ultimate strength for infinite long chains using these constants is 5 GPa... 

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