Acrylic Fiber properties
Basic physical and chemical properties of Acrylic Fiber:
It is important to know a little about the basic physical and chemical properties of acrylic
substrates and how these influence the choice of processing techniques. The following points
should be noted.
(1) Acrylic substrates can sequester iron and copper ions and once these are absorbed they are
very difficult to remove. Residual metal ions can cause fabric yellowing and dull optical
whites and bright pale shades; light-fastness may also be impaired.
(2) The use of strong alkali above the Tg of the fibre can lead to some problems with residual
alkali. Once alkali is absorbed, it is difficult to remove and may still be present when the
material is dried at elevated temperatures. These conditions will not be encountered in the
dyeing of 100% acrylic substrates but may well be in the dyeing of cellulosic blends.
(3) One of the attributes of acrylic substrates is that they can produce high bulk, and hence
aesthetically pleasing, yarns, garments and fabrics. In order to maximise these properties it is
important to be aware of the need to control tension and temperature.
(4) Processing tensions should be kept as low as possible during wet and finishing processes.
(5) The use of free chlorine-containing bleaches should be avoided at temperatures at or close
to the Tg of the fibre. Hypochlorite bleaching above the fibre Tg may well initially produce
a whiter substrate but almost invariably the fibre will yellow on subsequent drying at an
elevated temperature or on exposure to light. It is virtually impossible to remove residual
chlorine completely even after the most thorough antichlor treatments once acrylic
substrates have been exposed above their Tg.
The most important practical properties of an acrylic or modacrylic fibre to a dyer are the:
(1) base colour of the fibre and how stable this is to the dyeing process;
(2) rate at which the fibre will dye and the number of acidic end groups in the polymer chain;
(3) hot wet mechanical properties;
(4) resulting fastness properties of the dyed material.