316 Lubricant Additives: Chemistry and Applications
it was conducted in Rohm and Haas’ Philadelphia Research Laboratories. Bruson was exploring
the synthesis and possible applications of longer alkyl side chain methacrylates [1]. He had pro-
posed poly lauryl methacrylate as a product that might serve as a potential thickener or viscosity
index improver (VII) for mineral oils. The result of the work was the 1937 issuance of two U.S.
patents, for “Composition of matter and process” [2] and for “Process for preparation of esters and
products” [3].
11.1. 2 FIRST APPLICATION
Bruson’s invention did indeed thicken mineral oils, and it was effective in increasing viscosity at
higher temperatures more so than at lower, colder temperatures. Since this behavior infl uences
the viscosity–temperature properties or VI of a fl uid, these materials eventually became known
as viscosity index improvers (VIIs). Although PMAs successfully thickened oils, there were
other competitive thickeners of that time, which increased the viscosity of mineral oils; these
were based on poly isobutylene and alkylated polystyrene. The commercial success of PMA
was not at all assured. The driving force behind PMA eventually eclipsing the other commer-
cial thickeners of the era was PMA’s value as a VII rather than as a simple thickener of oils. In
other words, PMAs have the ability to contribute relatively little viscosity at colder temperatures
such as those that might be encountered at equipment start-up, but have a much higher contri-
bution to viscosity at hotter temperatures at which equipment tends to operate. This desirable
behavior enabled oil formulators to prepare multigrade oils that could meet a broader range of
operating-temperature requirements. The positive enhancement of VI ensured the future success
of PMAs.
11.1. 3 FIRST MANUFACTURE AND LARGE-SCALE APPLICATION
The commercial development of PMAs as VIIs lagged until the beginning of World War II, when
the U.S. government board rediscovered Bruson’s VII invention. The board was charged with
searching the scientifi c literature for useful inventions that might aid the war effort. When con-
sidering potential utility, they hypothesized about a PMA VII providing more uniform viscosity
properties over a very broad range of temperatures, particularly in aircraft hydraulic fl uids. The
fl uids of that era were judged to be defi cient particularly in fi ghter aircraft because of the exag-
gerated temperature/time cycles experienced. On the ground, the fl uids could experience high-
temperature ambient conditions and engine waste heat; and then after a rapid climb to high, very
cold altitudes, the fl uid might experience temperatures below −40°C. After successful trials of
the multigrade aircraft hydraulic fl uid concept, Rohm and Haas, in cooperation with the National
Research Defense Committee, rapidly proceeded to commercialize PMA VIIs and delivered the
fi rst product, Acryloid HF, in 1942. These multigraded hydraulic fl uids were quickly adopted by
the U.S. Army Air Corps and were followed by other multigraded hydraulic fl uids and lubricants
in ground vehicles that incorporated VIIs.
After the war, Rohm and Haas introduced PMA VIIs to general industrial and automotive
applications. Early passenger car engine oil VIIs were fi rst introduced to the market in 1946.
The adoption of “all season” oils in the commercial market was greatly infl uenced by two events.
First, the automotive manufacturers’ viscosity specifi cation introduction of the new designation
“W” (for winter grades); and then by Van Horne’s publication [4] pointing to the possibility of
making and marketing cross-graded oils such as the now well-known “10W-30” as well as other
cross-grades. By the early 1950s, use of multigrade passenger car oils became widespread in the
consumer market. Methacrylates played a major role in enabling the formulation of that era’s
multigrade engine oils. The use of PMA VIIs has since been extended to gear oils, transmission
fl uids, and a broad array of industrial and mobile hydraulic fl uids in addition to the early usage in
aircraft hydraulic fl uids.