Nylons analytical techniques

Hartness [100], working with XAS and HMS fibers in a PEEK matrix showed similar behavior. The similarities between PEEK and PP are probably greater than the differences in their crystalline structure. Beaumont [101] has shown that with HMS (treated) fiber, there is almost no pull-out, whereas with HMU (untreated) fiber, extensive debonding and pull-out take place. The pull-out lengths can be measured and using an analytical technique outlined by Phillips [102], values can be obtained for the nylon/fiber interfacial bond strength and fracture energies. 

Analytical techniques enabling polymers to be accurately structurally described are of the greatest importance, and the quantitative analysis of copolyamides (and copolyesters) by gas chromatography is now possible. A method for the determination of the degree of cross-linking in nylon-6 and -66, using 1,5-difluoro-2,4-dinitrobenzene has been reported, and kinetic studies on gel formation in molten poly(n-xylylene adipamide) have also been carried out. ... 

TEM is a very common analytical technique that can produce high resolution photographs of nanoparticles in polymer matrices. This technique can yield accurate information on the level of exfoliation, the distance between partieles, and the spacial distribution of nanoparticles. Figure 3.4 contains the TEM image of a well-exfoliated composite of montmoril-lonite in nylon 6. The clay plates appear as dark lines in a light gray matrix. The teehnique can also yield pictures of tactoids and disordered structures mentioned previously when discussing X-ray diffraction. 

Where impurities are present as microparticulate material filtration affords a convenient technique for solvent purification. The mobile phase containing added buffers or reagents may be filtered through a 0.5 pm or smaller filter to remove particulate matter that can damage the analytical system. The equipment for filtration is simple. Usually, it consists of an Elenmayer flask connected to vacuum and a reservoir in which a porous filter disk or membrane is placed. The porous disk is usually made from nonporous spherical glass beads (1-2 pm) and/or polytetrafluoroethylene (PTEE). Membrane materials are usually made from PTEE, cellulose, or nylon. To improve the efficiency of the separation process, the surface of the filter disks or membrane surface are often modified chemically, similar to that used for chemically bonded packing materials in RP-HPLC and/or SPE. In this case, the surface properties (hydrophobic or hydrophilic) of filters and/or membranes determine the extent of purification possible. 

The materials used for LFIA strips are nitrocellulose, nylon, polyethersulfone, polyethylene, fused silica, etc. A conjugate pad is where the analyte of interest forms a complex with the preimmobilized particles. Depending on the assay format, different types of particles may be immobilized in the conjugation pad ie, colloidal gold, colored or fluorescent particles, biomolecules, etc. In the detection pad, other specific biorecognition elements are immobilized and the interaction with the analyte is sensed using colorimetric, electrochemical, or another detection technique. The purpose of the absorbent pad is to wick the excess fluid so that higher sample volume can be used for better sensitivity. 

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