Basic Textiles VII
CHEMICAL FINISHING
Finishing: any operation in the manufacture of textiles that improves appearance/imparts
useful characteristics to the fabric. The finisher is generally responsible for the final fabric
width, weight, count, shrinkage. Finishing enhances existing desirable properties or new
properties.
Processes:
- Application of finish solution
- Evaporation of solvent or water (drying)
- Heating to activate chemicals (curing) padders
Expose fabric to solution of active chemical, followed by uniform drying to remove solvent,
curing active chemical by exposure to high temperatures. Chemical reaction takes place.
Binds finish to fabric.
Applicators:
- Padders
- Vacuum extractors
- Kiss and engraved roll applicators
- Foam
- Spray
Reactors (drying and/or curing):
- Dry cans
- Roller ovens
- Loop ovens
- Tenter frames
EQUIPMENT USED
SINGLE NIP PADDER
“dip” is the immersion of fabric through finishing chemical solution. “nip”
is point of contact of fabric between 2 squeeze rolls (“mangle”). One roller
is rubber and other metal, pressure determines percent wet pick-up
(%WPU). Also fabric construction and nature of fiber determines.
EX: polyester, finish solution is in spaces between fibers and yarns.
Cotton absorbs solution into fibers.
%WPU: weight of liquid picked up by fabric after padding as % of
original dry fabric weight. Normally between 75% and 100%.
Active finishing chemical = %WPU and concentration chemical in pad bath.
Normally concentration value is 10%.
, Basic Textiles VII
Vertical padder is more popular than horizontal padder because provides better view of
fabric at nip point.
DOUBLE DIP DOUBLE NIP PADDER
For thicker fabrics that are difficult to wet out or pile fabrics, use three roll
padder to improve wetting and penetration of chemicals. Fabric is double
immersed and double padded. Fabric is dry before first immersion (“wet-
on-dry finishing”). Can also be wet (“wet-on-wet finishing”).
OPEN TYPE VACUUM SLOT
Vacuum slots remove excess water from fabric. Usually for padding.
Control moisture level in wet-on-wet finishing. Increase drying speeds.
Allow application of finishing chemicals from higher bath concentration
by lowering wet pick-up. Removes lint from surface fabric (good for
printing).
Discharge coefficient (vacuum efficiency). The higher this number,
the more water is extracted from the fabric.
HERRINGBONE DESIGN
- For fabrics with stretch potential higher than 20% in warp and weft.
- For wovens or stable knits. Knits should be held in slack otherwise pulled
into open vacuum slot.
- Prevents suction but removes excess water.
- Ex: tricot, power knits (lycra, spandex)
KISS ROLL
Method for applying finish to one side of the fabric. The kiss roll goes
through chemical bath and transfers chemicals to fabric as it passes across
top of the roll. Fabric is never immersed in the bath.
Wet pick-up is determined by speed of roller rotation, speed of moving
fabric, viscosity of solution. 2 guide rolls hold fabric against kiss roll.
Moisture sensors monitor fabric wet pick-up.
EX: backing to upholstery fabric. Amount of finish cannot be precisely
controlled. Latex backing are not very costly.
ENGRAVED ROLLERS
Transfer finishing is same as kiss roll technique. Roll is engraved with
pattern. Rubber squeeze roll transfers finish from engraved roll to the fabric.
CHEMICAL FINISHING
Finishing: any operation in the manufacture of textiles that improves appearance/imparts
useful characteristics to the fabric. The finisher is generally responsible for the final fabric
width, weight, count, shrinkage. Finishing enhances existing desirable properties or new
properties.
Processes:
- Application of finish solution
- Evaporation of solvent or water (drying)
- Heating to activate chemicals (curing) padders
Expose fabric to solution of active chemical, followed by uniform drying to remove solvent,
curing active chemical by exposure to high temperatures. Chemical reaction takes place.
Binds finish to fabric.
Applicators:
- Padders
- Vacuum extractors
- Kiss and engraved roll applicators
- Foam
- Spray
Reactors (drying and/or curing):
- Dry cans
- Roller ovens
- Loop ovens
- Tenter frames
EQUIPMENT USED
SINGLE NIP PADDER
“dip” is the immersion of fabric through finishing chemical solution. “nip”
is point of contact of fabric between 2 squeeze rolls (“mangle”). One roller
is rubber and other metal, pressure determines percent wet pick-up
(%WPU). Also fabric construction and nature of fiber determines.
EX: polyester, finish solution is in spaces between fibers and yarns.
Cotton absorbs solution into fibers.
%WPU: weight of liquid picked up by fabric after padding as % of
original dry fabric weight. Normally between 75% and 100%.
Active finishing chemical = %WPU and concentration chemical in pad bath.
Normally concentration value is 10%.
, Basic Textiles VII
Vertical padder is more popular than horizontal padder because provides better view of
fabric at nip point.
DOUBLE DIP DOUBLE NIP PADDER
For thicker fabrics that are difficult to wet out or pile fabrics, use three roll
padder to improve wetting and penetration of chemicals. Fabric is double
immersed and double padded. Fabric is dry before first immersion (“wet-
on-dry finishing”). Can also be wet (“wet-on-wet finishing”).
OPEN TYPE VACUUM SLOT
Vacuum slots remove excess water from fabric. Usually for padding.
Control moisture level in wet-on-wet finishing. Increase drying speeds.
Allow application of finishing chemicals from higher bath concentration
by lowering wet pick-up. Removes lint from surface fabric (good for
printing).
Discharge coefficient (vacuum efficiency). The higher this number,
the more water is extracted from the fabric.
HERRINGBONE DESIGN
- For fabrics with stretch potential higher than 20% in warp and weft.
- For wovens or stable knits. Knits should be held in slack otherwise pulled
into open vacuum slot.
- Prevents suction but removes excess water.
- Ex: tricot, power knits (lycra, spandex)
KISS ROLL
Method for applying finish to one side of the fabric. The kiss roll goes
through chemical bath and transfers chemicals to fabric as it passes across
top of the roll. Fabric is never immersed in the bath.
Wet pick-up is determined by speed of roller rotation, speed of moving
fabric, viscosity of solution. 2 guide rolls hold fabric against kiss roll.
Moisture sensors monitor fabric wet pick-up.
EX: backing to upholstery fabric. Amount of finish cannot be precisely
controlled. Latex backing are not very costly.
ENGRAVED ROLLERS
Transfer finishing is same as kiss roll technique. Roll is engraved with
pattern. Rubber squeeze roll transfers finish from engraved roll to the fabric.
