Polymer fibre types

Figure 3.15 Chromatogram of fibre-type proteins on polystyrene gels having different pore sizes. Column A, PLRP-S 300 A, 15 cm x 4.6 mm i.d. B, PLRP-S 1000 A (polystyrene gel), 15 cm x 4.6 mm i.d. eluent, 15 min linear gradient from 20% of 0.25% trifluoroacetic acid to 60% of 0.25% trifluoro-acetic acid in 95% aqueous acetonitrile flow rate, 1.0 ml min-1 detection, UV220 nm. Peaks 1, collagen (Mr 120 000) and 2, fibrinogen (Mr 340 000). (Reproduced by permission from Polymer Laboratories data)...

When an X-ray beam passes through such a fibre perpendicular to its length, the pattern produced is of the same type as that given by a single crystal rotated about a principal axis. All orientations perpendicular to the fibre axis are already present in the specimen, so that the effect of rotation is produced. Examples are shown in Plate X. The reflections are less sharp than those produced by single crystals, for two reasons firstly, the orientation of the crystals in the fibre is not perfect, so that each spot is drawn out to the form of a short arc, and secondly, in most polymer fibres the crystals are so small that the reflections are inevitably more diffuse than those of la rge crystals (see p. 437). 

PP/silver nanocomposite fibres were prepared with the aim of achieving permanent antibacterial activity in a common synthetic textile. The fibres were melt-spun by coextmsion of PP and PP/silver masteibatches using general conjugate spinning. Masteibatches were made up of a mixture of PP chips and nano-sized silver powder. The antibacterial efficacy of spun fibres was high when the masteibatch was used as the sheath rather than the core. The antibacterial activity of nano-silver in fibres was evaluated after a certain contact time and calculated by percent reduction of two types of bacteria. Staphylococcus aureus and Klebsiela pneumoniae. DSC and wide-angle X-ray diffraction were used for analysis of stractuie, thermal properties and crystallisation behaviour of the spun fibres. SEM was carried out in order to observe particle distribution on the nanocomposite fibres. 17 refs. (2nd International Conference on Polymer Fibres, Manchester, UK, July 2002)... 

The compressive properties of a polypropylene mierofibre mat and a standard AGM were compared in one of the ALABC projeets diseussed above [27]. The findings are shown in Table 7.16. Although the eompressibility of the dry separator and especially the shrink-on-wetting look favourable, the capacities of eells assembled at 40 kPa and 80 kPa were signifieantly lower than for cells with hybrid separators (mix of glass and polymer fibres). Tear-down analysis revealed that this was due to release of acid from the separators. In the light of this phenomenon, no further work on this separator type was eondueted within the project. 

This chapter will provide the reader with a general introduction to the more common types of solid-gas (dust collection) and solid-liquid filtration mechanisms. The raw materials, polymers, fibres, and different types of fabric construction employed in filter media manufacture and some typical fabric finishing processes are discussed in detail. A brief look at filter market developments will also be considered. 

Phenomenological aspects of fibre fracture have been discussed elsewhere (see Kausch, 1987 for example). It suffices to remind that the details of the failure process are highly complex and depend upon many factors such as polymer structure, environment, type of loading and time. Molecular fracture does not occur to the same extent in all polymer fibres and the micromechanisms differ in different types of fibres. 

The time-dependent behaviour is different in the two types of highly oriented, chain-extended polymer fibres. Table 1 gives the results of studies in FIBRE TETHERS 2000 (1995), which were made because creep rupture is a concern in deep-water mooring of oil-rigs. The low-load creep in aramid fibres is due to a straightening of the initial. structure. It reduces in rate, even on a logarithmic scale, with time and is not a source of creep rupture. In Vectran, the creep is less and is absent after 10 days under load. 

As shown in the previous section, most polymer composites used in construction involve highly flammable matrices, such as polyester, vinylester or epoxy resins. Besides, if glass and carbon fibres are generally considered heat resistant, other type of fibres used for specific applications may also exhibit poor fire behaviour (aramid, polyolefins or other polymer fibres, for instance). Therefore, to meet the safety requirements specified in building codes and... 

Various types of fibres could be used in making filter fabrics they include glass fibres, synthehc fibres, ceUulosic fibres (eg, natural wood pulp fibres, viscose fibres, and Lyo-ceU fibres), wool fibres, metal fibres, ceramic fibres, high-performance polymer fibres (eg, inherenfly fire-resistant fibres, chemical resistance fibres, high-strength, and high-modulus fibres), microfibers, and nanofibers. 

Key properties that can influence the performance characteristics of a nonwoven needle-punched geotextile are fibre type polymer, diameter, length, etc. fibre quality fibre lubrication needle shape needle density depth of penetration of needle, needfing rate, and batt areal density (Venkatappa Baneijee, 1997). 

---