Polymers as components of gear lubricants

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.  

Future Trends

If the business of providing proper lubrication for  gears and transmissions were a  static one, people  would  lose  interest in it, and  there  would  be no  purpose  in this volume. However, as indicated by the just preceding, there are problems in connection with gear lubrication and gear lubricants. While  the immediate reaction  to a complaint  or a  problem  of this  sort  is to  blame  the lubricant, it  should be  again  pointed  out  that  perhaps  only  ten  per cent  of   such  complaints are due to  deficiencies  in either  the lubricant or the  application. In spite of this , the  industry  does  have problems and since they  will not  always solve  themselves, it  is necessary  to give  thought  to the  future  when  solution of  the  immediate  problems will be possible  but new  ones  will be  confronted.

Since a little  adversity is good  for the soul, these  problems stimulate  thought  and are the  cause  of many  improvements  and  advancements  in   all industry. In the lubrication of   gearing, the problems do not always take the form of complaints but often of suggestions. Whatever the form,  such  questions do indicate that  modification of  not  only  present  products  but  also  present  thought may be  necessary if the  lubrication industry  is  to  play  a part  in continually improving  the world.

No matter how  did  wild  dreams about providing  different  or better lubricants for gears may  be,  they  would  come  to naught  if  practical considerations are not  kept  in mind. These  include  the economy  of   the suggestion,  the  availability  of  the  necessary  components of the  composition, the  ease of  application, compatibility  with other  materials, and  acceptance  by  other industries  and  by the public. Any or all of these factors may change with time; hence, it is well to dream.