Gel-spun polyethylene

Chemically Resistant Fibers. Fibers with exceUent chemical resistance to corrosive and/or chemical warfare agents or extreme pH conditions (eg, very acidic or very alkaline) were initially used for protective clothing. However, appHcations for filtration of gases and Hquids in numerous industrial faciHties are now the more important. For example, PPS is suitable for use in filter fabrics for coal-fired boilers because of its outstanding chemical and heat resistance to acidic flue gases and its exceUent durabUity under these end use conditions. Many high tenacity fibers are also chemically inert or relatively unaffected under a variety of conditions. Aramids, gel spun polyethylene, polypropylene, fluorocarbon, and carbon fibers meet these criteria and have been used or are being considered for appHcations where chemical resistance is important. 

Production. Recognition that the shish-kebab fibers produced by the surface-growth procedure result from the deformation of a gel-like entangled network layer at the rotor surface led to the development of gel-spun polyethylene fibers. The fiber is made by the solution spinning method. The polymer is... 

T300, T50 and PI00 are carbon fibers Spectra 1000 is a gel-spun polyethylene and SSE PE is a solid state extruded polyethylene. Other polymers on die plot have stiff backbones and a liquid crystal character],... 

Commercially available polyethylene fiber has a degree of crystallinity between 70 and 80% and a density 0.97 gcm . There is a linear relationship between density and crystallinity for polyethylene. A 100% crystalline polyethylene will have a theoretical density, based upon an orthorhombic unit cell, of about lgcm . A totally amorphous polyethylene (0% crystallinity) will have a density of about 0.85gcm . Khosravi et al. (1995) used nitric acid attack on gel-spun polyethylene fibers to observe structural imperfections such as fold, molecular kinks and uncrystallized regions. Raman spectroscopy has been used to study the deformation behavior of polyethylene fiber. This technique gives peaks for the crystalline and amorphous states of polyethylene (see Chapter 9). 

The results obtained by drawing gel spun polyethylene fibres at different tempe-... 

The results obtained by drawing gel spun polyethylene fibres at different temperatures are shown in Fig. 5. It can be seen that the relationship between Xmax, and >-1/2 predicted by Eq. (3) holds to a good approximation. Furthermore, the intercept at = 1 for a draw temperature of 90 °C was found to be 3.8, in good agreement with the value of 3.7 estimated above. The higher values of gel at higher temperatures were attributed to chain slippage. 

Altering the orientational order within polymer films and libers has long been used to exploit the inherent molecular-level anisotropy. Fully extended conventional polymers (e.g., gel-spun polyethylene... 

The solution to this puzzle could be found from an analysis with solid-state NMR. Figure 5.157 shows, using the technique applied to the analysis of MBPE-9 with Fig. 5.152, that in gel-spun polyethylene fibers there are two signals from the... 

The condis phase in fibers contributes considerably to the modulus and strength, as was discussed for poly(ethylene terephthalate) in terms of structure and properties in Figs. 5.68-72 and 5.113-115, respectively. The gel-spun polyethylene has little... 

For use in implants, polypropylene is the fiber of choice for hernia and prolapsed repair meshes and monofilament sutures. Gel-spun polyethylene, on the other hand, with ultra-high strength and stiffness but stretch of the order of only 2%, has been considered mostly for use as very fine suture materials. 

Because of the small size of the terephthaloyl and the oxyethyleneoxy groups, it is most likely that the mesophase is an oriented condis phase, rather than a liquid crystal. The sizes of the three phases range from nanophases to microphases. A similar mesophase has also been suggested for gel-spun polyethylene, where a mobile preferentially trans component has been found in addition to the much less mobile crystal... 

High tenacity and Aramids, gel spun polyethylene. Tires, antiballistics, ropes,... 

Yan R, Hine P J, Ward 1 M, OUey R and Bassett D (1997) The hot-compaction of Spectra gel-spun polyethylene fibre, J Mater Sci 32 4821-4832. 

One of these commercial fibers is gel-spun polyethylene from ultra-high-molecular-mass polymer (e.g.. Spectra, Honeywell) with extremely high modulus [for PE, Tg = -36°C, = 141.4°C, A//(° = 293 J/g (Gaur and Wun-... 

The use of reinforcing fillers and fibers in polymers to improve their mechanical properties is commonly encountered in polymer technology. Conventional fibers such as carbon fibers, glass fibers, gel-spun polyethylene fibers, and aramids are routinely used in composites of a range of different polymers (Chronakis 2005). The improvement in modulus and strength achieved by using even low levels of a reinforcing fiber in a composite is impressive. Some of this improvement is due to the properties at the fiber/matrix interface and therefore dependent on the surface area of the... 

WF Wong, RJ Young. Analysis of the deformation of gel-spun polyethylene fibres using Raman spectroscopy. J Mater Sci 29 510-519, 1994. 

The novel high-modulus, high-strength fibers, especially aramid and gel-spun polyethylene, deserve a special status. These yarns are spun from solution again, and we will discuss the specific modifications of the old wet spinning process that were required to produce yarns stronger than steel . 

Synthetic cellulose yams were developed between 1880 and 1910, first from a nitrocellulose solution, and later as copper rayon and "viscose rayon . The cellulosics are often called half-synthetic because the raw material is a natural polymer. The most important fully synthetic yarns were developed between 1935 and 1942 - polyamides (PA66, PAG), polyester (PET), and acrylic yarns (PAN copolymers). Another half-century later, many high-performance fibers were introduced, for example aramid (PPTA), gel-spun polyethylene, and carbon fiber. 

Most fibers are semicrystalline. A few of them - aramid and gel-spun polyethylene - approach 100% crystallinity. Examples of the fiber stmcture of PET and PPTA are shown in Figure 17.5. All fibers have a uniaxial organization properties in the direction of the axis are completely different from those in the cross-direction. This is an essential difference from other polymer materials. 

The word paracrystalline is used for aramid and gel-spun polyethylene. Amorphous regions are no longer present rather, the discussion is about defects in the crystal regions. Fiber moduli approach theoretical crystal moduli and shrinkage is virtually absent. Indeed, this is a completely different class of materials. 

Gel-spun polyethylene is produced by DSM in cooperation with Toyobo (Dyneema) and Honeywell, formerly Allied Signal (Spectra). From the relevant patents it is fairly obvious that different solvents are used a volatile solvent in the Dyneema process and a nonvolatile solvent in the Spectra process. 

Gel-spun polyethylene is too low-melting (about 140°C) to be applied in rubber reinforcement. In composites the curing temperature should not exceed 130°C, and a surface treatment is required for sufficient adhesion. Finally, performance under constant load is restricted because of creep limitations. 

Carbon fibers are used almost exclusively in composites. Two main types are offered one with high strength (1.9-3.9 N tex tenacity, 140 N tex modulus) and one with a high-modulus (2.2 N tex tenacity, 280 N tex modulus). Carbon fiber moduli are much higher than those of aramid and gel-spun polyethylene. 

Over the IS years since the original Raman deformation studies upon polydiacetylene single crystals, the technique has been developed and refined to involve the study of a wide range of different high-performance polymers and other materials. These have included rigid-rod polymer fibres [19-21], carbon fibres [22-24] and ceramic fibres [2S-27]. This present chapter will concentrate upon recent research concerning the use of Raman spectroscopy to follow the deformation of aramid fibres and gel-spun polyethylene fibres and the possibility of the extension of the technique to isotropic polymers, and also the important and developing application of the method to the study of the deformation of fibres within composites. 

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