Compatibility of lubricating greases with plastics and elastomers

With the increasing use of plastics and elastomers in many applications, the compatibility of lubricating greases with these materials is becoming more important. Whether these components are lubricated, or they may come into contact with a lubricating grease, it is important that there are no interactions between these materials, i.e. that they are compatible. Common signs of incompatibility may include volume expansion of the plastic due to lubricant penetration into the structure, resulting in softening of the polymer and loss of structural stiffness, or absorption of plastic constituents by the lubricant, which may lead to surface cracking.

The tables below show the compatibility of various elastomers and plastics with the main types of oil. These tables provide an initial overview of whether incompatibilities are to be expected, but we recommend that each case is considered individually, as there are variations in the composition of the base products for lubricants as well as elastomers and plastics. 

Standard tests to determine whether there has been a change in properties typically assess shrinkage, swelling and hardness changes. Changes in tensile strength and resistance or elongation at break are also measured as required. These tests are carried out in accordance with DIN 53504 and DIN ISO 1817. Thermoplastics are tested for stress cracking according to DIN EN ISO 22088-3 using the bent strip method. The limits for each parameter are specified by the plastic manufacturer or determined by the user based on practical conditions of use. Determination of volume and hardness changes is sufficient for an initial assessment.