Polyacrylonitrile fibres

Scouring is particularly necessary for yams which are to be dyed in pale and medium shades as grey patches may appear due to soiling and lubricant present in the fibre. 

Before scouring high bulk acrylic yams on cones are relaxed in saturated steam at about 100 C for 20 mm or in hot water. The hanks may be relaxed during dyeing also. Fabrics may be given dry heat treatment to impart some stability against creasing and to relax the material. 

Generally, scouring of modacrylic fibres is not always necessary. However, scouring and desizing may be carried out in a similar manner to that regular acrylic 

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In addition to poly(methyl methacrylate) plastics and polyacrylonitrile fibres, acrylic polymers find widespread use. First introduced in 1946, acrylic rubbers have become established as important special purpose rubbers with a useful combination of oil and heat resistance. Acrylic paints have become widely accepted particularly in the car industry whilst very interesting reactive adhesives, including the well-known super-glues are also made from acrylic polymers. 

The commercial appearance of phenolic resins fibres in 1969 is, at first consideration, one of the more unlikelier developments in polymer technology. By their very nature the phenolic resins are amorphous whilst the capability of crystallisation is commonly taken as a prerequisite of an organic polymer. Crystallisability is not, however, essential with all fibres. Glass fibre, carbon fibre and even polyacrylonitrile fibres do not show conventional crystallinity. Strength is obtained via other mechanisms. In the case of phenolic resins it is obtained by cross-linking. 

Among the various types of polymers the problem of chemical modification of polyacrylonitrile8 (PAN) and polyacrylonitrile fibres attracts the ever growing attention of numerous investigators. 

The proposed model for creep rupture based on the condition of maximum shear strain and the Eyring reduced time model explain the observed relations concerning the lifetime of aramid, polyamide 66 and polyacrylonitrile fibres. However, with increasing temperatures, in particular above 300 °C, chemical degradation of PpPTA also determines the lifetime. Furthermore, the model... 

Cationic FBAs are used to brighten polyacrylonitrile fibres. The brightening of acrylic fibres is carried by the exhaust method at an acid pH, usually in the presence of sodium chlorite or bisulfite bleach. Pyrazolines produce very high whites but are unstable to bleach and therefore the quaternary benzimidazoles are the preferred class, e.g. (3.65) and (3.66). 

A growing specialty application for acrylonitrile is in the manufacture of carbon fibres. These are produced by pyrolysis of oriented polyacrylonitrile fibres and are used to reinforce composites for high-performance applications in the aircraft, defence and aerospace industries. Other minor specialty applications of acrylonitrile are in the production of fatty amines, ion exchange resins and fatty amine amides used in cosmetics, adhesives, corrosion inhibitors and water-treatment resins (Brazdil, 1991). 

Heterocycles have also been introduced into the 3-position by condensation of a heterocyclic acetonitrile with an o-hydroxybenzaldehyde, as for example in the quaternized triazolyl derivative (95) which is used on polyacrylonitrile fibres. 

Chemical metallisation and galvanisation as a method for development of electroconductive polyacrylonitrile fibres... 

The aim of the investigation and development described in this chapter is the development of electroconductive polyacrylonitrile fibres. In this first section, a preliminary study is described to optimise the common poly-... 

Metallisation of fibres is not only a physical process determined by absorption capacity of the fibres for the metal and diffusion capacity of the metal in the fibre structure, but also depends on chemical parameters such as chemical structure of the fibres, presence of functional groups, reactivity of the fibre and the metal, oxidation state of the metal and the presence, necessity and reactivity of supporting chemicals (e.g. reducing agent). Therefore, it was necessary first to study metallisation at different types of fibres in order to investigate which structure is most useful for further research. In this respect, viscose, cotton, natural silk and polyacrylonitrile fibres were investigated because of their different structure and properties and their availability in the New Independent States of the former Soviet Union (Uzbekistan, Kazakhstan, Kyrgyzstan). 

According to their chemical constitution and stabilization synthetic fibres show differing degrees of sensitivity to light, for example aliphatic and aromatic polyamides are more sensitive and polyacrylonitrile fibres less so. Apart from... 

The pioneer in the field of truly synthetic fibres was Carothers, who demonstrated that two comparatively simple compounds derived from phenol, namely, hexamethylenediamine and adipic acid, could be caused to polymerize to form a potentially fibrous polymer. This was spun into yarn which was successfully placed on the market as nylon. Shortly afterwards ethylene glycol and terephthalic acid were condensed to a polymer from which Terylene or Dacron was made. Ethylene is a by-product in the cracking of petroleum and is the starting point in the manufacture of vinyl chloride and acrlyonitrile, from which Vinyon and the various polyacrylonitrile fibres respectively are spun. 

Pure polyacrylonitrile fibres have hit ll tensile strenj th, but the separation of the molecules by side chains in tlie co iolyiiiers teiuls -to reduce tenacity. A compromise is j enerally iKcepted with a breaking strain of about 4 g per denier, and an extension at break of 30 to 40 per cent. J he fibres vary considerably in the shape of their cross-sections when viewed under the microscope, although the longitudinal surface lews of the fibres are all alike (Figs. 7.15, 7.16, and 7.17). 

I he combined nitrogen in the polyacrylonitrile fibres tends to retain chlorine and dechlorination for twenty minutes at 60°C (140°F) in a solution containing 1-5 lb per 100 gallons of sodium sulphite is necessary. 

Where W represents the wool molecule. Not much w ork has been done on the adsorption of basic dyes by animal fibres, but Glenz and Beckmann (Melliand Textilber., 1957, 38, pp. 296, 783, and 1152) have studied the exhaustion isotherms of basic dyes with polyacrylonitrile fibres. The curves which are obtained correspond with the Langmuir type of equilibrium, except that they are steeper in the initial stage. It is believed that this is because the dye cations are adsorbed extremely rapidly at the... 

Polyacrylonitrile fibre sorbent impregnated with Polyarsenazo N has been applied for preconcentration of trace amounts of U in natural waters [53]. Trace quantities of U in seawater were concentrated on siiica gel columns [54] and on cellulose sorbent impregnated with Arsenazo III [55]. Chelate sorbents for preconcentration of uranium have been treated in detail [56,57]. 

Journal of Applied Polymer Science 65, No. 10,6th Sept. 1997, p. 1955-66 MODIFIED POLYACRYLONITRILE FIBRES Buchenska J... 

Details are given of a two-stage method for obtaining polyacrylonitrile fibres with antibacterial properties. The method consists of the incorporation of carboxylic groups into the fibres followed by fibre impregnation with gentamycin, neomycin, or penicillin solutions. Characterisation was undertaken using FTIR and proton NMR. 29 refs. 

Azo dyes derived from diazotized 5-amino-1,2,4-thiadiazoles are used as dyestuffs for polyester and polyacrylonitrile fibres. 

A generic name for polymers produced from acrylic acid/derivatives, mostly polymethylmethacrylate, or polyacrylonitrile fibre. 

Fibres with about 94% carbon produced by pyrolysis of Rayon, polyacrylonitrile fibres or pitch. 

Polyacrylonitrile. A sub-group of acrylic plastics. The blow moulding, injection moulding, and fibre grade polyacrylonitriles are generally copolymers of acrylonitrile. Trade names Barex (USA), Soltan (B). Trade names of polyacrylonitrile fibres Acrilan (USA), Crumeron (H), Dralon (FRG), Orion (USA). 

Polyacrylonitrile fibres can be flame-retarded by vinylidene chloride, vinyl chloride, or vinyl bromide added in the course of polymerization. Some attempts were made with red phosphorus as well. ... 

High-temperature polymers can be produced from polyacrylonitrile fibres by annealing (cf. Section 5.1.5). 

By vacuum pyrolysis of polyacrylonitrile fibres, black heat-resistant fibres of cyclic structure ( black orlon ) is formed through the following supposed mechanism ... 

R. Moreton and W. Watt, The spinning of polyacrylonitrile fibres In clean room conditions for the production of carbon fibres, Carbon, 12, 543-554 (1974). 

Watt W, Chemistry and physics of the conversion of polyacrylonitrile fibres into high modulus carbon fibres. Watt W and Perov BV eds., Vol, Strong Fibres, Elsevier, Amsterdam, 327-388,1985. Johnson W, The structure of PAN-based carbon fibres and relationship to physical properties. Watt W and Perov BV eds., Vol 1, Strong Fibres, Elsevier, Amsterdam, 389-444, 1985. 

Johnson W, Hot stretching of carbon fibres made from polyacrylonitrile fibres, Proc 3 bit Corf on Industrial Carbons and Graphite, Soc Chem Ind, London, 447-452, 1970. 

Watt W, Chemistry and Physics of the Conversion of Polyacrylonitrile Fibres into High Modulus Carbon Fibres, Watt W, Perov BV eds.. Handbook of Composites Vol 1, Strong Fibres, Elsevier... 

Watt W, Johnson W, Mechanism of the oxidation of polyacrylonitrile fibres, Nature, 257, 210-212, 1975. 

Mathur RB, Bahl OP, Sivaram P, Thermal degradation of polyacrylonitrile fibres. Current Science, 62(10), 662-669, 1992. 

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