Bakelite degradation in oil
Bakelite degradation in oil
(OP)
Was after some information on the above topic. I have a plastic component which I suspect is bakelite, which has been operating in a mineral oil environment for 20+ years (temp ~70°C).
The component has failed with minimal deformation. I'm trying to determine whether degradation in service has lead to a reduction in properties.
My understanding is that bakelite may be attacked by organics (oil), which may dissolve the bakelite and leave it more susceptible to rupture.
What tests can be performed on the failed piece to determine whether (and how far) degradation had occurred?
Thanks in advance
The component has failed with minimal deformation. I'm trying to determine whether degradation in service has lead to a reduction in properties.
My understanding is that bakelite may be attacked by organics (oil), which may dissolve the bakelite and leave it more susceptible to rupture.
What tests can be performed on the failed piece to determine whether (and how far) degradation had occurred?
Thanks in advance





RE: Bakelite degradation in oil
Although I do not know the exact processing conditions, mechanical loading, possible reinforcements, fillers etc., the 20+ years sounds reasonable (if we do not consider weathering conditions, such as moisture and UV exposure).
The bakelite resin can be tested according to ASTM D570, using fit-for-purpose sample dimensions and temperature condititions.
Note that current physical-chemical simulations are so able to deal with the above problem - in a much more efficient manner.
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Regards,
RE: Bakelite degradation in oil
It turns out that the material isn't bakelite, but probably a glass fibre reinforced ABS. My understanding is that these composites have some inherent brittleness.
The query was regarding a failure analysis, in light of the above we're taking a different approach and looking at other components.
RE: Bakelite degradation in oil
Indeed, ABS with glass reinforcements is a sligthly different story. ABS it resistant to aliphatic hydrocarbons, but not to aromatic (such as benzene, toluene, ethylbenzene, xylene) and chlorinated hydrocarbons. ABS shows stress cracking in the presence of certain organic compounds.
The above may be an important factor.
Regarding intrinsic mechanical properties: impact and toughness of ABS are outstanding. Impact resistance does not fall off rapidly at lower temperatures. Stability under limited load is excellent. However when impact failure takes places, the failure is ductile rather than brittle. Water has little effect on the mechanical properties of ABS.
RE: Bakelite degradation in oil
I am NOT sure whether bakelite is chemically corroded by mineral oil (i.e. by some sort of corrosion front). However, the lighter species of the mineral oil mixture will solve in the bakelite resin. This will soften the polymer, which will reduce the mechanical properties.
The rate of softening will depend on the diffusion rates of the lighter species in the mixture. Since diffusion rates are raised exponentially by temperature, here the system temperature - being substantially above ambient - is an important ageing factor).
Although I do not know the exact processing conditions, mechanical loading, possible reinforcements, fillers etc., the 20+ years sounds reasonable (if we do not consider weathering conditions, such as moisture and UV exposure).
The bakelite resin can be tested according to ASTM D570, using fit-for-purpose sample dimensions and temperature condititions.
Note that current physical-chemical simulations are so able to deal with the above problem - in a much more efficient manner.
RE: Bakelite degradation in oil
ABS is attacked by many solvents as mentioned above and is subject to oxidation at elevated temperatures.
There are many grades available and the properties vary considerably because of significant variations in the properties of the base resins and because of significant variations in reinforcement packages from grade to grade.
Diffusion rate is a mute point after 20 years as it will be approaching equilibrium at any reasonable temperature in a much shorter time frame than 20 years.
ABS would not be my choice for a part that was to spend a lot of time immersed in oil.
Cotton fabric, wood flower filled phenol formaldehyde (one trade name Bakerlite) is commonly used in machine parts subject to contact with oil. It has very good long term thermal and bearing properties and has exceptional rigidity and dimensional stability. It has low elongation at break even when new.
For a part to endure very long life at 70 deg C immersed in oil, I would seriously consider a very well stabilised glass filled nylon or Polyester, but the choice will depend on many factorsalmost none of which are declared in the OP.
Regards
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RE: Bakelite degradation in oil
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RE: Bakelite degradation in oil
This one may be to bluntly. It all depends on the frequency/period/cycling of the actual chemical exposure. If there was a recent change in e.g. pipeline operation, the chemical exposure and resulting penetration depths (especially of the lighter species), can be one of the root causes for material failure.
Regards,
RE: Bakelite degradation in oil
Regards
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RE: Bakelite degradation in oil
Now, I definitely agree with you!
Thanks.
Rodney