Polymers find application in gear
lubricants both as additives and as actual fractions of the base fluids.
Specific types of polymers used as additives will be mentioned later. Since the
fluids in gear lubricants consist
primarily of mineral oils or of
asphaltic materials, any polymers
added should be compatible
with the major
ingredients. Likewise, polymerization
of the added compounds should
be complete so that no
further thickening occurs
in service even
if the mixture
is subjected to
some heat. Most polymeric
materials will break down under shearing
action of gear to
products of lower
molecular weight and
hence any initial
bodying effect may
be partly lost
after use.
Although the polymers may be
miscible with lubricating oils, special procedures may be necessary to introduce
them into gear oils. Thus the grade of
polyisobutylene which is used
to give tackiness
or stringiness to oils is about
the nature of, but tougher than, crepe rubber. Consequently this polymer is
dispersed by a rubber mill in lubricating oil and the solution known as paratac
is available to compounders. Also
most grades of polyethylene
are of such
a nature that only
prolonged heat and agitation
will disperse them in
lubricating oils.
The following polymers have
been suggested or actually
used as components of fluids
for gear lubricants:
polyisobutylene of various molecular weight; styrene-polyisobutylene; polyethylene ;and resins recovered from
mineral oils. With the continued
investigation and production of
new or
modified polymers it seems reasonable that increasing
use of such
materials can be expected in gear lubricants.
