Fiber samples, running

Nylons. Figure 11 shows two small, single nylon fiber samples run by TMA. Despite the small size, all the major characteristics could be evaluated the dehydration contraction, the glass transitions, the processing temperatures and the melt. These two similar samples of nylon displayed similar qualitative behavior characteristic of the nylons, and from the temperatures of the transitions it is clear that Nylon 6 and Nylon 6-6 can be easily distinguished by their melting curves using TMA. 

Earlier attempts to use the AFM for mechanically stretching chromatin fibers have run into a rather unexpected artifact. Long native chromatin fibers isolated from chicken erythrocytes, or fibers assembled in vitro from purified histones and relatively short, tandemly repeated DNA sequences were deposited on mica or glass surfaces and pulled with the AFM tip [69,70]. In such stretching experiments the scanning of the sample in the x- and y-direction used for imaging was disabled, and the cantilever-mounted tip was allowed to move only in the z-direction, i.e., upwards and downwards, away and towards the surface. When the AFM tip is pushed into the sample, it may attach to the sample by non-specific adsorption upon retraction it stretches the sample and force-extension curves are recorded (see Fig. lb for an explanation of a typical force curve). 

This is a development of the above where a fiber-optic linked hqnid sample transmission cell is integrated with the sample fast loop cabinet (Figures 5.24 and 5.25). There can be multiple sample streams, take-offs and fast loops, each with its own separate fiber-optic transmission cell. The analyzer can either be local with short fiber-optic runs to the sampling cabinet(s), or remote, where a safe area location for the analyzer module may be feasible, but at the cost of longer, potentially less stable fiber-optic runs. This system avoids physical stream switching. 

Fiber degradation should be monitored after every ten sample runs (see Critical Parameters). 

The materials used included dyed and undyed yarn and fiber samples obtained from the manufacturers and fabric and other polymeric materials from the marketplace. The samples were encapsulated without preparation and the experimental conditions are noted on each figure. Unless otherwise noted, the DSC samples were run in an atmosphere of dry nitrogen. 

A sample run is shown in Fig. 10 where the formation and the rupture of meniscus around the carbon fiber is indicated. The stage motion is stopped at A after advancing and at B the stage is lowered for a receding contact line. In this case there is no hysteresis. The increase in force before rupture is the end effect where the liquid is suspended at the edge and the force goes through a maximum. 

Running Fiber Samples. When running fiber samples in constrained mode, the steel plate on which the fiber is wound up should be as thin as possible. With thick steel plates, excessive baseline sloping will occur. 

Once this condition is reached, the primary coating s glassy expansion curve from -50 °C to -30 °C and the secondary coating s rubbery expansion curve from 125 °C to 90 °C can be extrapolated upward and downward, respectively, until they meet the linear line extending from the expansion curve between 0°C and 75 °C (dashed line. Fig. 4.36). This process yields glass transition temperatures near -20 °C and 87 °C. DSC measurements at 15°C/min on this same optical fiber sample indicated that glass transition temperatures occur at -31 °C and 78 °C. In normal practice with the probe seated, the final stable heating run would be selected and isolated in a separate plot for determination of Tg and CLTE values. 

It should be noted that in the case of imaging probes (Section II.E.2.b), there are usually two environments associated with each probe installation. The probe head, which contains sensitive optical components, is located just outside the process. The probe optic, typically a customized lens and window combination, is the part which is actually immersed or in contact with the process material. Needless to say, the probe optic usually experiences a more severe environment than the probe head. For nonimaging probes [181,190,200], the filters, if any, or other optics are immersed in the process and have to be compatible with that environment. For both imaging and nonimaging probes, the fiber cable run from the sampling point to the analyzer represents a third unique environment. 

Pyrolysis gas-liquid chromatography (pyrolysis-GLC) was also used to characterize the fiber samples. The pyrolyzer used was a Chemical Data Systems 190 Pyroprobe with a platinum coil pyrolyzer. One to two millimeters of the fiber samples were pyrolyzed in clean quartz pyrolysis tubes. The pyrolysis temperature was 770°C, applied for ten seconds. The column used was a 60 meter, wide-bore, Carbowax 20M capillary column with an inside diameter of 0.75 mm (Supelco Inc.). In order to accommodate the capillary column it was necessary to modify the Perkin-Elmer 3920B gas chromatograph which was used. This instrument was designed for two packed columns. Because of the very low carrier gas flow rate used with capillary columns, it was necessary to introduce a make-up gas at the detector end of the capillary column to provide sufficient carrier gas flow through the detector. The make-up gas system consisted of a stainless steel line running from one of the injector ports to the effluent end of the capillary column. To reduce the contact of the pyrolysates with metal surfaces the... 

In. samples were taken with a small spatula from a 10 cm x 10 cm area, while the 1-6 and 6-12 In. samples were taken using a 2 In. diameter soil core sampler. Air samples were taken at the downwind edge of each bed by running a high volume air sampler with a quartz fiber filter backed with 120 mL of XAD-4 resin for 2 hr. 

---