The
resistance of plasticised PVC,
Nylon, Polyester Elastomer Lining,
low density Polyethylene &
Polyurethane to a wide range
of chemicals is listed in the
following table. The symbols
used to denote performance are
as follows:-
Satisfactory
Some attack
or absorption: the material
may be considered for use
when alternative materials
are unsatisfactory and where
limited life is acceptable.
When PVC is to be used with
such chemicals fullscale
trials under realistic conditions
are particularly necessary.
Unsatisfactory:
so rated because of decomposition,
solution, swelling, loss
of ductility etc. of the
samples tested.
In
order to give guidance, the resistance
of PVC to some chemicals has been
predicted from its resistance
to other chemicals which have
a similar composition. Such predictions
are shown using an asterisk (*)
with the symbols listed above.
It may be safely assumed that
chemical resistance decreases
with both increasing temperature
and with increasing concentration
of reagent, and that the reverse
is also true.
No valid assumptions can be made,
however, if the temperature and
concentration move in compensating
directions. The rating ‘some
attack or absorption’
(symbol
-
)
should not be assumed to
apply at conditions different
from those shown.
Chemical
resistance of polyurethane
hoses and composite hoses
sleeved with polyurethane.
The polyurethane is not
recommended for continuous
use in contact with water
above 40°c (or solutions
containing water above 40°c)
because of its hydrolising
effect. Hydrolysis can also
occur with long exposure
to:
a)
high humidity
at elevated temperatures,
b)
acid and
alkali solutions,
c)
aerated water,
d)
fungi and
bacteria.
Some
substances having a satisfactory
rating may give swelling but this
is usually minimal. The assumption
should not be made that this indicates
deterioration of the polyurethane.
