Polymeric fibers, structural studies

Ergungor describes the application of on-line Raman spectroscopy and neural networks to the simultaneous prediction of temperature and crystallinity of nylon-6 nanocomposites as a function of cooling rate. The authors prefer their neural network approach because they make use of information in the entire spectrum rather than from a few bands as most studies have done.84 Van Wijk etal. of Akzo Nobel obtained a patent on the use of a Raman spectrum of a polymeric fiber to determine dye uptake and other structural or mechanical properties based on previously developed models.85... 

Investigations by X-ray methods have indicated that alginic acid possesses a fiber structure analogous to that of cellulose.86 An estimate of the molecular weight was obtained by Heen87 from a study of the viscosity of solutions of the acid in 2 JV sodium hydroxide. The values found, (14,100-15,400), corresponded to a degree of polymerization of about 80, but these were considered to be approximations only, as it was uncertain whether or not Staudinger s formula could be applied. 

For studying structure of polymer and influence of introduction of additives HZ-1 HZ-2 HZ-4 the method of micro photographing has been applied. Cuts of polymeric fibers photographed at 40 multiple increase, on a microscope "Polar" which had a special nozzle for photographing. 

Jaeger et al. studied the morphological characteristics of electrospun polymeric fibers in the diameter range of 200-800 nm (Jaeger et al. 1998). Koombhongse et al. spun different fibers and reported flat ribbon I i ke structures and branched fibers (Koombhongse et al. 2001). The electrospun fibers were between 1 and 3 pm in diameter. 

Swierenga and co-workers [79,80] in two articles described in detail their development of the calibration model used for PET measurements. Van Wijk et al. [72] summarized from their work that Raman spectroscopy can be used for determining the dye uptake or measuring one or more structural parameters or mechanical properties of polymeric fibers. Based on the results of their work, the authors stated that Raman spectroscopy was useful for studying melt-spinning thermoplastics, such as polyester, polyamide, polyolefins, and alternating copolymers of carbon monoxide and olefins so-called polyketones and, in addition, for polymers which are spun from solution such as cellulose, aromatic polyamides, polyketones, aromatic polyesters, and polyolefins. 

Munoz-Guerra also studied stereoregular polyamides fully based on d- and L-tartaric acid [73]. The bispentachlorophenyl esters of both 2,3-di-(9-methyl-tartaric acids (22 and 23) were condensed with (2S, 3S )-2,3-dimethoxy-l,4-butanediamine (41) to obtain optically active (PTA-LL) and racemic (PTA-LD) polytartaramides. Fiber-oriented and powder X-ray studies of these polyamides demonstrated that PTA-LL crystallized in an orthorhombic lattice, whereas PTA-LD seemed to adopt a tricUnic structure. In both cases, the polymeric chain appears to be in a folded conformation more contracted than in the common y form of conventional nylons. 

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