Viscose Rayon Preparation

Viscose Rayon Preparation

Manufacturing of Viscose Rayon:

• Possible sulphur residues can generate reducing conditions – destroying or changing the shade of dyestuffs
• After initial skin formation, the core of the fibre decomposes, hardens and shrinks. Viscose fibres are therefore characterised by an irregular, serrated skin and cross section. The skin is said to consist of many small crystalline regions. The core, on the other hand, develops a coarser crystalline structure.
• Differences in the ratio of skin to core impact on fibre properties and dyeing behaviour. Dye diffusion is therefore
  crucial to dyeing speed and extra kinetic energy is needed for dye penetration – especially when swollen to its maximum by heat.

Properties of Viscose:

• Viscose has lower tenacity in both wet and conditioned state than cotton – more care is necessary to prevent fabric breakages and tears in wet processing.
• Viscose has greater elongation in both wet and conditioned state than cotton – it will be stretched or distorted more under tension.
• Viscose and Modal fibres are supplied in a pure state and with a higher degree of whiteness than cotton. Bleaching is only required for a full white or pastel shades. Viscose/cotton blends require bleaching baths with a reduced chemical content.
• The water retention value (swelling index) of viscose is very much higher than that of cotton. In aqueous liquors, viscose fibres tend to swell more strongly than Modal fibres or cotton. This swelling process happens very quickly and is almost complete after ten seconds at the lower temperature range.
• Fabrics become much more stiff when wet because the fibres are so swollen. In their swollen state, viscose fibres can become set to a certain extent. This is called hydro plasticity.