To produce colored Fabric whether dyed or printed needs pre-treatment
of those fabrics of those fabrics before dyeing and printing. The
pretreatment operations involved for cotton fabric are described
systematically below:
Singeing
: it is the process of
burning out projecting hairy fibres from surface of the grey fabric by
assigns the fabric through a gas flame. Both sides of the fabric are
burnt out by the flame. It helps in subsequent chemical process of the
fabric. After dyeing or printing of singed fabric, brightness and luster
of color and fabric becomes better.
Desizing:
it is the pr4ocess of removing starch materials present in the gray
fabric. Generally enzyme is used to degrade and remove the starch
present in the grey fabric. If those size materials are not removed from
the grey fabrics, then the subsequent chemical treatments on the fabric
will be irregular, which will cause he defective dyeing and printing.
Scouring:
It is the process of removing natural impurities present in the
cotton fibre. The natural impurities are pectin’s, pectos, ash, wax,
mineral compounds, etc. if those impurities present in the cotton fibres
are not removed, then it will be difficult to dye or print the fabric
uniformly. Normally caustic soda ash is used as main reagent fro
scouring of cotton fabric.
Bleaching:
It is the process of removing natural coloring matters present in the
cotton fibre. For his purpose, hydrogen peroxide, bleaching powder or
other bleaching agents are used. Hydrogen peroxide is the best and most
commonly used bleaching agent. If this bleaching treatment is not
carried out before dyeing or printing hen the color yield and shade
matching may be a great problem.
Mercerization:
It is a special chemical pre-treatment on cotton fabric t improves
the properties and performance of cotton fabric. The cotton fabric is
treated under tension in the 20% caustic soda solution which is called
mercerization many properties of cotton fabric is improved, some of them
are mentioned below:
Increases fabric strength
Increases absorbency power
Increases fabric luster
Increases fabric softness and handle property
Reduces dye consumption
Reduces chemical consumption in dyeing.
Increases absorbency power
Increases fabric luster
Increases fabric softness and handle property
Reduces dye consumption
Reduces chemical consumption in dyeing.
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