Nuclear magnetic relaxation in polypropylene fibres

Abstract

Three types of drawn PP fibres have been investigated by nuclear magnetic relaxation methods. The two minima observed in both the temperature dependence of T, and Tzeff are related to the well known pand a-processes, respectively.The results of the experiments show that in particular the crystalline regions are influenced by drawing. Kernmagmtische Relaxation in PolypropylenfasernMit Hilfe der kernmagnetischen Relaxation wurden drei Typen gereckter PP-Fasern untersucht. Die beiden Minima in den Temperaturabhangigkeiten von T, und Tzeff sind dem 8bzw. dem a-ProzeD zuzuordnen. Die Ergebnisse der Experimente zeigen, da5 durch die Reckung insbesondere die kristallinen Bereiche beeinfluJ3t werden. H3epnoaaztmmnaa penaxcay us e nonunponunenoebzx eonomax MeTOAOM RMP H3YYeHbI TPH THna RbITJTHYThIX ~OJIHnPOIlHJIeHOBbIX ROJIOKOH. ABa MHHHMYMa H a KpMBOfi 3aBHCA-MOCTII T I II Ea,#,@ OT TeMnepaTypM npnnncbmamcn npoqeccaM 8-H a-penaxcaqnu. IIonyseHHbIe p e~y n b~a~b~ no-Ka3bIBaH)T, YTO IIpOqeCC BbITIImKH OKa3bIBaeT BJIIIJTHUe o c o 6 e~~o H a KpHCTaJIJIH9eCKMe o 6 n a c~u .The influence of different preparation conditions upon formation of the morphological structure of polypropylene fibres was studied by X-ray method, scanning electron microscopy, and small-angle light scattering technique. It was found that the formation process and the deformation of the morphologic structure in polypropylene fibres changed when using the traditional and the high velocity technologies, respectively. Die morphologische Struktur von PolyprvpylenfasernDer EinfluS verschiedener Herstellungshedingungen auf die Bildung der morphologischen Struktur in Polypropylenfasern wurde mittels Rontgenbeugung, Scanning-Elektronenmikroskopie und Kleinwinkel-Lichtstreuung untersucht. Es wurde festgestellt, da8 der BildungsprozeB und die Deformation der morphologischen Struktur in den Polypropylenfasern sich beim Ubergang von der traditionellen zur Hochgeschwindigkeitstechnologie andern.

NMR and dynamic mechanical studies of drawn polypropylene fibers

“…It was reported that the drawing increases macromolecular orientation in crystalline and non-crystalline regions, which results in the increase of the optical birefringences Dn [8]. We suppose that the shift of the temperature T min is connected to the restriction of the segmental motion arising from the higher macromolecular orientation in non-crystalline regions of the polymer under study [3]. The increase of the relaxation times T 1, min with increased drawing ratio k can be related to the change of crystallinity of the drawn fibers.…”

“…In partially crystalline polymers the values of the spin -lattice relaxation times T 1, min are determined not only by the spin -lattice relaxation but also, due to the spin diffusion, by the relative amount of the non-crystalline (relaxing) polymer chains. It was reported that an increase of the crystallinity gives rise to an increase of T 1, min [3,9]. The values of crystallinity X c , optical birefringence Dn, temperatures T min and relaxation times T 1, min are listed in Table 1.…”

“…However, little attention has been paid to the influence of drawing on the relaxation behavior of the PP fibers and films studied by the measurement of the temperature dependence of spin -lattice relaxation times T 1 . It was observed that, for instance, the minimum of the temperature dependences of the spin -lattice relaxation times T 1 shifts to higher temperatures with increased drawing [3].…”