Stringiness Agents

Where it  is desirable  to  increase  the  adhesiveness or  tackiness of gear  oils, high  molecular  weight  hydrocarbon  polymers or  copolymers, such  as Paratac  are  added. As little as 0.01 per cent of this compound is noticeable. Solutions of natural  crepe  rubber in oil give much the same  effect but  lose  their  tacky character upon  storage.

Rubber Swell due to Gear oils

Where gear  oils  are  in  contact  with  rubber gaskets, seals, etc., the  action of  the  fluid on the  rubber compositions is of  importance. Consequently a Federal Test Method, 3604-T, has been set up. Such a test  can  be  varied as to  temperature, time and the  polymer     composition tested  depending upon  the    actual  service conditions of the  gear oil.

Thus, for ATF the following procedure is used. Sections of piston seals made from Acadia 3612 rubber compound are subjected to hot transmission fluid. Measurements of volume and hardness are made before and after the test. Two  seals are  cut  into  eight  sections each  and  the  sections  are  suspended  in  test  tubes  containing the lubricant and  held in a bath  at  300 degree F for  70  hours. The  sections are  then  cooled for  thirty  minutes  to  one hour in a  fresh  portion of the  test  fluid maintained at room  temperature. After wiping dry, the final volume and durometer readings are taken.

Minimum action of gear oils on components of mechanisms

Well refined mineral lubricating oils have little if any action on most metals, particularly ferrous metals. It is only upon prolonged use at elevated temperatures that such oils may from compounds which will act upon metals. Since such oil changes can be retarded or almost completely arrested by the use of oxidation inhibitors and also metal deactivators or pacifiers can be included, there should be little concern about the action of straight mineral oils upon the metal components with which they come in contact.

What we are concerned with here is the action on parts made from other materials, such as paper, plastics, rubber, etc. Seals are likely to be made from rubber, either artificial or natural, and any deterioration of the compositions due to the lubricant should be at a minimum. Many seals consist of compounded materials, such as “neoprene,” and it is found that oils high in aniline points, as are most high V.I. oils, will have little effect on this compound.

Automatic transmission mechanisms may be found to contain paper and “Nylon” parts. In future devices which will require transmission fluids, a greater variety of components may be used. The safest course when supplying oils for contact with unusual materials is to have the fluids pretested to determine their suitability.