PEN fibers

In addition to the crystal forms, X-ray scattering studies indicate that when unoriented PEN fiber was drawn at 120 °C ( 7 g), a mesophase is generated. In this form, the molecular chains are in registry with each other in the meridional direction but not fully crystallized in the equatorial direction. This conclusion was based on the presence of additional meridional peaks not accounted for by the crystal structure obtained by X-ray scattering. The mesophase is a intermediate phase and its existence is strongly dependent upon the processing conditions consequently, it could have implications with respect to the properties of commercially produced fibers and films, since it appears to be stable and not easily converted to the crystalline form, even at elevated temperature [25, 26], The mesophase structures of PET, PEN and poly(ethylene naphthalate bibenzoate) were compared by Carr et al. [27], The phase behavior of PEN and PEN blends with other polymers has also been studied [28-32],... 

Kim and Lee 2000 investigated the thermal properties of electrospun PET and PEN fibers made from melts (Kim and Lee 2000). 

Cakmak, M. and Kim, J. C., Strucmre development in high speed spinning of polyetliylene naphtlialate (PEN) fibers, J. Appl. Polym. Set, 64, 729-747 (1997). 

Figure 7.44 TMA curves for poly(ethylene-6-naphtha-lenedicarboxylate) (PEN) fibers spun at high speed [16]. Numerals on curves are spinning speeds (see the table below)...

PEN mnltifilament fibers are commercially available from several polyester fiber prodncers. These include Teijin in Japan, Honeywell (formally AlliedSignal) in the United States and Enrope, Kosa in Europe, and Hyosimg in Korea. PEN fibers are produced in a melt spinning/post-drawing process similar to that used in PET fiber manufacture. All production to date is in the form of continuous multifilament yarn, although staple and monofilament fabrication have also been reported. 

PEN-based fibers extend the performance of polyesters. PEN fibers have excellent heat resistance, modulus, and dimensional stability relative to PET and demonstrate better retention of mechanical properties in a hot/wet environment and offer improved chemical resistance versus PET fibers (see Polyesters, Fibers). With naphthalate modification, polyester fibers can meet the application requirements, which are currently served by other high performance industrial fibers such as rayon, nylon-6,6, aramids, poly(phenylene sulfide) (PPS), and even steel. 

There are multiple opportunities for PEN fiber use in tire construction. Figure 9 is a typical tire construction schematic, showing the three different tire cord textile layers, carcass, belt reinforcement, and cap ply, where PEN fiber can be used. 

Figure 2.57. Melting curves of as-spun and drawn PEN fiber (draw ratio = 5.2) as can be seen, the as-spun fiber is amorphous, and the crystalUnity of the drawn fiber is 50% on the basis of the heat of fusion [From Saw et al. (1997) reprinted with permission of Society of Plastics Engineers],...

Figure 9.25 Equatorial and azimuthal X-ray diffraction profiles of undrawn (lower) and drawn (upper) PEN fibers spun with LIB.

Equatorial X-ray diffraction profiles of as-spun PEN fibers as a function of (a) threadline length (b) molecular weight of polymer (Wu et al, 2000). Here IV represents intrinsic viscosity. 

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