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The majority of natural rubber latex products are now manufactured
by dipping. A former, which in the case of gloves looks like
a hand, and is typically made from porcelain - glass for condoms
- is dipped into a tank of a coagulant, dried and then dipped
into a tank of concentrated latex. The latex will probably
contain the agents required to protect and vulcanize the latex
films. The latex on the former is then then dried in a long
drying tunnel. Leaching (to remove excess compounding ingredients
and protein) takes place in the ewt gel state whilst the product
is still on the former. Full drying and vulcanization follows
leaching. The operation tends to take place as a continuous
process and the finished products are stripped from the formers
at the end of the line. Flocking (for lined household gloves)
takes place as an additional dipping operation. After stripping
the products are washed to remove any residues and may be
subjected to chlorination and other surface treatments .
The major dipped product is gloves, but condoms, balloons
and catheters are also manufactured in this way. The bulk
of gloves are consumed by the healthcare industry and are
broadly of two types: surgical and examination. Specialized
household and industrial gloves are also manufactured. Many
of the latter are either manufactured from synthetic elastomers,
or have a protective outer-layer manufactured from synthetic
rubber. Industrial gloves tend to be much thicker than medical
gloves. Electricians' gloves are thicker and may contain
a coloured layer to show the wearer if the integrity has
been lost through wear. Balloons are a specialized activity:
they are usually coloured and may have messages printed
on them.
Other products manufactured from latex include catheters
and condoms (prophylactics), thread (used on a large scale
in garment manufacture), foam (used in pillows and mattresses).
Many adhesives are based on latex. Some carpets and rugs
may be backed with latex foam. Latex is produced in the
form of sheet and is used for some swimming caps.
Latex thread is manufactured by extrusion of the latex
through fine capilliaries. The filaments are dried and vulcanized
in a long oven. Most of the tread is covered with fabric
before being incorporated into a wide variety of garments.
Latex films may be used as a casting medium: in its simplest
form the latex is coated onto a master: this is stripped
off once it has dried and the film is used to act as a mould
to cast materials like plaster of paris. Usually the mould
is built up by several layers of latex. The technique is
used to make quite complex castings and is important in
archeology where copies can be made of scultures, etc. Films
can be cast as a continuous process to form latex sheet
which is used in a number of applications. It is also possible
to cast cellular latex in porous plaster of paris moulds
.
In recent years an allergy problem has arisen in a small
number of individuals with the use of latex products. It
is believed that this small genuine health problem is greatly
exaggerated by the manufacturers of competitive materials,
the promise of rewards from litigation, etc. Furthermore,
many of those afflicted are also prone to be allergic to
many common foods (such as bananas and nuts) and other materials:
indeed their allergies may stem from these foods and nor
from latex. It must be emphasised that latex allergy is
not nearly as serious as the deadly peanut allergy which
kills many infants each year.
Latex films form an excellent barrier to pathogens. Latex
films are a major protection against the spread of AIDS
and many other serious diseases. Unlike many alternative
materials now sometimes being risk there is no suggestion
that the raw material may contain carcinogens or may produce
carcinogens during disposal by combustion (as in the case
of vinyl gloves).
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