quote:
But something that comes in granular form doesn't sound like a candidate for the base of a fully formulated motor oil.
IMHO, that is a suprising statement. As a fuel engineer you should know the answer to that question, assuming engineers take enough chemistry these days to know the difference between the various phases of chemicals.
Let's take an example: When the VII oelfin copolymer arrives (OCP), it is basically a block of rubber, being made from polyisobutylenes of very high molecular weights. To transform it into an additive, one heats it and then dissolves it in any number of suitable solvents, from light mineral oils to cycloaliphatics. So I could say, gee, I don't want that in my oil cause it looks like rubber. But chemistry further transforms it into a useful additive to keep your oil from thinning at high temps.
Most additives and base oils, including esters for formulating, are shipped in liquid form for immediate blending. Some customers may require additives and other components to be shipped in powder or crystal form because they have chemists who make special recipes for their special application, such as possibly printing machinery. But 99% of all base oils and additives are shipped in liquid form.
Now some very good scientific sources that I rely on are found in the
Journal of Synthetic Lubricants and a number of texts, one of them being
Synthetic and High-Perfromance Functional Fluids, edited by Ronald Shubkin [PAO and Friction Modfier chemist and tribologist (PhD) for Ethyl Corporation]. Another one is the CRC handbook text,
Handbook of Lubrication and Tribbology, Vol. III, edited by E. Richard Booser, Chemist and Tribologist (PhD) of Pennsylvania State University.
[Now unless you are a chemist or formulator, I wouldn't recommend rushing out and purchasing these books; they cost upwards of $275 each].
I will quote some info and then attempt to put into laymens terms. In order to do so, I will simply say R1, R2, R3 for the respective references.
R1, R2: Hydrolytic Stability:
"The hydrolysis of the ester, that is to say, their cleavage into an alcohol and an acid, has been the subject of many discussions in the past. However, this reaction has proved less disadvantageous in practice than had originally been feared. Ester lubricants must be hydrolytically stable because they are exposed to humid atmospheres during use and and come into contact with appreciable quantitites of mouisture in many applications. The hydrolytic stability of esters depend on two main features: processing and molecular geometry.
Acid value
degree of esterification,
catalyst used during esterification.
"Esters have to have a low acid value, a very high degree of esterification, and low ash level before the effects of molecular geometry will begin to assert themselves.
Molecular geometry can affect hydrolytic stability in several ways....."
"The hydrolytic stability of neopolyols can generally be regarded as good, and superior to that of dibasic esters."
Translation: Hydrolitic stability is not a problem today, and esters are today
designed to be stable in the presence of moisture and acids, by their molecular engineering.
R1, R2: Elastomer Compatibility:
"Elastomers [synthetic rubbers as in seals] that are brought into contact with liquid lubricants will undergo an interaction with the liquid that is diffusing through the polymer network. There are two possible kinds of interaction: chemical interaction and physical interaction... Chemical interactions of elestomers with esters are rare."
Translation: The polymer network here is the polymer of the seal material. Interactions of seal materials with esters for lubricant oils are rare. That's why lubricants are tested for seal leakage in machines.
R1, R2: Polyols (Polyolesters): (general Information)
"Polyols are made by reacting multifuntional alcohols with a monofunctional acid....They are, however, much more stable than diesters, and tend to be used instead of diesters where temperature stability is important. A general rule of thumb is that a polyol is thoguht to be 40-50 C more thermally stable than a diester of the same viscosity. Esters give much more lower coefficients of friction values than those of both PAO and mineral oil. In general, polyol esters based on TMP or or PE give lower values [of friction] than diesters."
For those just tuning in, there are three major polyol esters: pentaerythritol esters, di-pentaerythritol esters, Tri, Qantinary-pentaerythritol esters, Trimethyl Propane esters (TMP), and Neopentylglycol esters (NPE). A fairly new one is the TME ester discussed earlier. All are very hydrolitically, thermally, and elastomerically stable.
On the topic of metal loss by various fluids:
From
Lubrication Engineering, Volume 35, Table 4, Bench oxidation tests for steel, aluminum, copper, and lead catalyst, 163 C, 10 hours;
A 4 cSt mineral oil by itself shows a lead loss of 201 milligrams,
a 4 cSt PAO by itself shows a lead loss of 561 mg,
a 5 cSt alkylated aromatic (AN) shows a lead loss of 558 mg,
a 5.1 cSt dibasic ester shows alead loss of 11 mg,
and a 4 cSt polyol ester shows a lead loss of 40 mg.
So this oxidation test contradicts the one shown by Primus.
In the same paragraph of R4, "Proper additive selection is necessary to obtain acceptable engine oils from both mineral oils and synthetic base stocks."
In other words, whatever base oil you use, proper additive selection must be "tuned" to the type of base stock or mix of base stocks you are using.
[ August 07, 2004, 10:37 PM: Message edited by: MolaKule ]
