Water Proofing
Water proofing is nothing but preventing the passage of both air and water through a fabric.Purpose
For certain uses such as
Tarpaulin, Umbrella cloth, Rain coat fabric etc. it is required to give this
type of finish as these type of fabrics are generally used against the air and
water in the normal life. So they should have some property to prevent both air and water passing through them. This finish makes the wearer
feel uneasy and uncomfortable as the air circulation is not there
PRINCIPLE
A finish on the surface of the fabric should be formed for the prevention of air and water hen a uniform coating o suitable substances such as rubber is produced on the surface of a fabric. the interstices between the warp and weft yarns are blocked by the continuous film or substance and both water and air will not pass through the treated fabrics. It is a chemical and property giving FinishRequirement
The fabric should not become unnecessarily stiff and the fabric should have soil release or soil repellent property.
The fairish should not
alter the fastness properties or dyed material, feel, strength etc., of the
fabric
Method
By 2 methods, it can be
carried out.
1. Methods by which hydrophobic substances are deposited on the cloth
2. Methods by which the fabric itself becomes
hydrophobic
Chemical use
1. Vulcanised natural rubber
2 Oxidized oils of
varnishes
3 Polyvinyl chloro
acetate.
4. Polyvinylidine Chloride
5. Cellulose acetate.
6. Cuprammonium hydroxide
solution
PROSESS
(A)The simplest method of water
proofing is it coating of fabric with rubber as a thin film
DISADVANTAGE
1 unwanted stiffness and
harshness.
(B)The application of Natural oil will also produce this finish.
(B)The application of Natural oil will also produce this finish.
ADVANTAGE
No cracks or brittleness
Disadvantage
it is not permanent.
(C) Coating of Water Impermeable substances like
pitch asphalt and molten waxes produce water proofing
Advantage
It will give excellent
Disadvantage
Many desirable properties
of the fabrics will be destroyed
(D)Using Synthesis Resins we can produce this
finish.
E.g. Polyvinyl chloro
acetate
Cellulose acetate
Polyvinylidine
chloride
( E) Water proofing with Wax Emulsion. It can be
applied on cotton, linen, wool, silk fabrics. Aluminum Acetate is used along
with the wax emulsion. There are two steps involved in producing this finish
First Step
Wax emulsion – 1-3 kg
Water - 50
litter
Pad the material with the
wax emulsion solution.
Second step
In wet condition
Aluminium acetate 1-3 kg
Water - 50 liters
Impregnate the fabric and squeeze thoroughly Then dry the fabric in a tenter or on a drying range at 110-120°C
PROCESS SEQUENCE
Pad – dry - Calendar