Sulfur fiber


The sulfur fiber or polyphenylene sulfide (PPS) is characterized by unusual toughness and good load-bearing capabilities. The fiber-forming substance in the case of sulfur fiber is a long-chain synthetic polysulphide with at least 85% of the sulfide linkages attached directly to two aromatic rings.


Sulfur fiber


Fiber formation

The raw material for sulfur fiber is p-dichlorobenzene and sodium sulfide. The conversion of the raw material into fibers consist of three stages. Those are :

(a) Production of polyphenylene sulfide polymer.
(b) Conversion of the polymer into the fiber by melt spinning
(c) Curing of the fiber for conversion into a tougher material

The polymer is produced by Wurtz Fitting condensation of p- chlorobenzene and sodium sulfide. The monomers and solvent, mostly polar, are fed into a polymerization reactor. Polymerization takes place at elevated temperatures. Once polymerization is complete, the solvent is stripped and recycled.
The polymer is then washed with water to remove sodium chloride and dried. The fiber is formed from the polymer by melt spinning technique at 300°C. The as-spun fiber can be drawn to 3.5 - 4.0 times at 100°C. 

After drawing the fiber can be converted into tougher material by curing process. Curing can be done at 250°C - 280°C in the presence of a small amount of air. Curing modifies the characteristics of the fiber-like
(i) an increase in molecular weight,
(ii) Cross-linking,
(ii) increase in toughness,
(iv) resistance to solvents like a loss in solubility and
(v) change in color from off-white to brown-black.

Proparties


The physical properties of sulphur fibre is given in Table
  1. Density (g/d)                    1.37
  2. Moisture regain (%)         0.6
  3. Tenacity (g/d)                   3 - 3.5
  4. Breaking Elongation (%)  25 - 30
  5. Initial modulus (g/d)         30 - 40
  6. Elastic recovery        100% at 2%; 96% at 5% and 86% at 10%


The fibers exhibit outstanding resistance to heat, retain more than 70% of original strength after being exposed to 200°C for 5000 hr. The fiber also shows outstanding resistance to acids, alkalies, bleaching agents and solvents except hot concentrated sulphuric acid and nitric acid.

Application

The generic name of this fiber is Ryton, produced by Philips Petroleum Company, USA. The fiber is used for fuel gas filtration, wet filtration, flame- retardant clothing and upholstery.




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