Technical Papers

Performance and Selection of Pour Point Depressants

Authors:            Phil Hutchinson 

E-Mail:                 phil.hutchinson@degussa.com

presented at:    LUBMAT
                            University of Lancashire
                            Preston, UK
                            June 14-16, 2006

Mineral base stocks contain waxy hydrocarbons that come out of solution
when temperature decreases. They form a three-dimensional wax crystal
network that can totally immobilize the oil. In formulated engine oils some additives
have a "waxy" or crystalline structure and further contribute to the formation of a
crystal network that impairs oil flow. Waxiness is evidenced at low temperature by
higher pour-point, yield stress and viscosity compared to a wax and additive free oil.
Inadequate oil flow to critical parts of the equipment may result in costly failures and
must be avoided by selecting the appropriate type and content of Pour Point
Depressant (PPD).

Selection of a suitable PPD must take into account many factors. These include the
PPD type and addition rate, the base stocks used, the influence of other additives and
the different cooling rates and shear rates to which the oil will be submitted in service.

As new, more diverse base-stock types are used, more waxy additives are utilized and
ever more stringent low temperature requirements on fresh and used oils are imposed,
the selection of a suitable PPD is becoming increasing challenging. Key aspects for the
proper selection of PPDs are presented in this paper.