Polyamide fibre, filament

Clear viscous aqueous solution. Highly effective size for filament polyamide yarns. SYNCOL F25 exhibits very high adhesion to polyamide fibres producing warps of high weaving efficiency at relatively low application levels. 

Polyamide fibres can be dyed with both cold- and hot-dyeing reactive colours in a liquor containing 4 per cent of the weight of the goods of acetic acid 80 per cent. The load is entered at 40°C (104°F) and the temperature brought up to 95°C (203°F), after which dyeing is continued for 1 hour, or more, if necessary. The reaetive dyes are satisfactory on staple yarns where differences in the affinity of the polyamide fibre are randomized. In continuous filaments any irregularities in the yarn are not covered. 

A distinctive structural feature of PpPTA and other para-aromatic polyamide fibres is the pleated sheet, which is shown in Fig. 13c, 13d and 13e. It was for the first time observed by Ballou in dark-field images taken from meridional reflections of the ED pattern [132]. This phenomenon has been extensively studied by Dobb et al. [125]. The pleated sheet consists of parallel-oriented chains, which are hydrogen bonded along the direction of the crystallographic b-axis. They are usually oriented perpendicular to the surface of the filament, i.e., in the circular cross-section the b-axes are directed preferably along the radius, as shown in Fig. 14. The angle between adjacent planes of the pleat is about 170° and the distanee between two pleats is about 250 nm, but both values may vary along the radius of the fibre cross-section. 

Polyester fibres are also tougher than polypropylene, and are again used where oxidising conditions are present, but on this occasion acidic conditions preclude the use of nylon. Polybutylene terephthalate (PBT) is a particularly tough variation but, like Polyamide 11, is also only available in monofilament form. On the other hand, unlike polypropylene and polyamide, all polyester fibres/filaments are severely degraded by strong alkaline conditions, the ester link in the molecular chain being attacked as shown in Fig. 7.9. 

Procesring of Polyamides.—Fibre Formation, Structure, and Properties. The equipment used for production of fibres by wet spinning of limited quantities of materials has been described, together with physical characterization methods for spun filaments of poly(m-phenylene adamantane l,3 dicarboxamide). ... 

As stated above, conventional synthetic fibres may be rendered inherently flame retardant during production by either incorporation of a flame retardant additive in the polymer melt or solution prior to extrusion or by copolymeric modification before, during, or immediately after processing into filaments or staple fibres. Major problems of compatibility, especially at the high tanperatures used to extrude melt-extruded fibres like polyamide, polyester, and polypropylene and in reactive polymer solutions such as viscose dope and acrylic solutions, have ensured that only a few such fibres are commercially available. A major problem in developing successful inherently flame retardant fibres based on conventional fibre chemistries is that any modification, if present at a concentration much above 10wt% (whether as additive or comonomer), may seriously reduce tensile properties as well as the other desirable textile properties of dyeability, lustre and appearance, and handle, to mention but a few. 

Industrial Applications. The wetting of fibres is an essential step in the production of synthetic textile filaments, such as polyamides and polyesters. 

By comparison, as other polymer types are of higher density and generally more expensive, they tend to be used where their physical and/or chemical properties significantly out-perform those of polypropylene. For example, fibres and filaments in the polyamide family, whilst unable to compete with polypropylene in strongly acidic conditions, are notably tougher and more durable than polypropylene. As a result, they are often found in less demanding chemical environments where high resistance to harsh abrasive... 

In recent history in Europe, textile viscose filament end-uses are receiving increased competition (resulting in phasing out of capacity) by cheaper competitive yams based on polyester and polyamide, whereas viscose staple fibre and viscose tyre cord keep a strong position. 

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