CHEMICAL BONDING PROCESSES
In Chemical bonding
process interlocking of fibers are take place by the application of a chemical
binder. The most frequently used chemical binder are water-borne latex. Latex
binders are made from vinyl materials, such as polyvinylacetate, polyvinylchloride,
styrene/butadiene resin, butadiene, and polyacrylic. Chemical binders are
applied to webs in amounts ranging from about 5% to as much as 60% by
weight.
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| CHEMICAL BONDING |
Properties Desired in a
Binder:-
The required properties
can be varied depending on the end-uses.
1.
Strength: The strength of a nonwoven fabric is more
closely related to the strength of the applied binder.
2. Adhesion
to Fibers: Even though the
mechanism of adhesion is not completely understood, the adhesion strength of
the binder-to-fiber bond has to be considered.
3. Resistance
to washing/ Drying cleaning: Some nonwoven products need durability in cleaning processesaccording
to their end-uses.
4.
Resistance
to aging: The binder should be
stable and not be degraded in the fabric during storage and use.
5. Good
color and color retention: Diverse ranges of colors are required, and the colorfastness and
yellowing problems should be considered.
6.
Flexibility/handle: The some movements of fibers should be
allowed,
especially when a
soft hand is desired.
7.
Minimum film forming temperature: At this temperature a
bonding film
will
dry without cracking which will occur if the temperature falls below this
point.
It can be reduced by adding softeners or optical brighteners.
8.
Economical: Minimizing the cost is an ongoing requirement.
9.
Glass or brittle temperature is the average
temperature of the range in
which the polymer passes from being hard and
brittle to being soft and
rubber like. This temperature will give an
indication of the feel, the
flexibility and the hardness of bonding film.
10.
Other
special requirements: Such
as Flame resistance, resistance to chemicals, air, oxygen, light, heat, etc.
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