Note: Descriptions are shown in the official language in which they were submitted.
2 0 2 9 ~ 0 9
ELECTROR~EOLOGICAL F~UIDS
This invention relates to electrorheoloyical
fluids ~ERFs), i~e. fluids which exhibit a significant
change in flow properties when exposed to an electric
field. These fluids are also known as "electric field
responsive fluids," "electro-viscous fluids" or "jammy
fluids."
Early studies of electrorheological fluids (ERFs)
demonstrated that certain suspensions of solids (a
"discrete," "dispersed" or "discontinuous" phase) in
liquids (a "continuous" phase~ show large, reversible
electrorheological effects. These effects are generally
as follows: in the absence of an electric field,
electrorheological fluids (ERFs)exhibit Newtonian flow
properties. Specifically, the shear stress (applied
force per unit area) is directly proportional to the
shear rate applied (relative velocity per unit
thickness). When an electric field is applied, a yield
stress phenomenon appears and no shearing takes place
until the shear stress exceeds a minimum yield value
which increases with increasing field strength, i.e. the
fluid appears to behave like a Bingham plastic. This
phenomenon appears as an increase in apparent viscosity
of several, and indeed many, orders of magnitude.
37,283A-F -1-
~ - . , .
-2- 2Q~
ERFs change their characteristics very rapidly
when electric fields are applied or released, typical
response times being on the order of 1 millisecond. The
ability of ERFs to respond rapidly to electric signals
make them uniquely suited for use as elements in
electromechanical devices. Often, the frequency range
of a mechanical device can be greatly expanded by using
an ERF element rather than an electromechanical element
having a response time which is limited by the inertia
of moving mechanical parts. Therefore, ERFs offer
important advantages in a variety of mechanical systems,
particularly in those which require a rapid response
between electronic controls and mechanical devices.
A range of devices have been proposed to take
advantage of the electrorheological effect. Because of
the potential for providing a rapid response interface
between electronic controls and mechanical devices, it
has been suggested that these fluids be applied in a
variety of mechanical systems such as electromechanical
clutches, fluid-filled engine mounts, high-speed valves
with no moving parts, and active dampers for vibration
control, among others.
As used herein~ the texm "dielectric" refers to
substances having very low electrical conductivity, if
any. Such substances generally have conductivities of
less than 1 x 10-6 mho per centimeter. While a number
of theories have been proposed to explain the electro-
3 rheological effect, a comprehensive theory explaining
all of the observed phenomenon has not yet been
developed.
There yet exists a need for an ~RF that will
operate at the relatively high temperatures encountered
37,283A-F -2-
2~2~
--3--
- in commercial applications, while requiring a low
electric field strength to produce a strong rheological
response and wherein the discrete phase is present in
low concentration. In ERFs which depend on the presence
of ~ree water or adsorbed water, the use of high
temperature is detrimental in that it tends to drive out
the water and reduce the effectiveness of the fluid.
We have now prepared novel electrorheological
fluids (ERFs) which do not require the presence of water
in order to be effective.
These novel ERFs comprise a continuous liquid
phase characterized as a dielectric fluid having a
relatively low dielectric constant and a disperse phase
characterized as either:
(a) a particulate solid of small non-conductive
particles bearing an aprotic coating, said coating
having a relatively high dielectric constant, applied to
the surface of the particles, or
(b) as being a very small particle size
crystalline LMMH (herein referred to as "LMMH"), or
(c) as being a very small particle size
crystalline LMMH (LMMH) having an aprotic coating
applied to the surface of the particles.
As used herein, the expression "relatively low
dielectric constant" of the dielectric continuous phase
is used to contrast it with the higher "relatively high
dielectric constant" of the dielectric disperse phase.
In some embodiments of the present invention,
ERFs utilize particles o~ crystalline LMMHs (LMMHs) as
37,283A-F -3-
'
'
~4~ 2~2~
- the discrete phase. ~hese L~MHs may be represented by
the formulae:
I MgxAly(OH)z, and
II LimDdT(OH) (m~2d~3+na) (An)a
where in Formula I:
x represents an average value of l.7, y
represents an average value of 0.5, and z represents an
average value of 5; and
where in formula II:
m represents the number of Li cations present; D
represents divalent metal cations; and d is the number
of cations D in the formula; ~ represents trivalent
metal cations; A represents monovalent or polyvalent
anions other than OH- ions; a is the number of anions A
in the formula; n is the valence of A; and where
(m+2d~3+na) is equal to or greater than 3. It will be
understood that since "n" represents a negative value
and "a" represents a positive value, then n times a (na)
will be negative. These LMMHs are preferably prepared
by an instantaneous ("flash") coprecipitation wherein
soluble compounds, e.g. salts, of the metals are
intimately mixed (using non-shearing agitation or
mixing) with an alkaline material which supplies
hydroxyl groups to form the mixed metal hydrous oxide
~ 30 crystals. A distinguishing feature of the present
; composition is that the crystals are essentially
monolayer, or one layer of the mixed metal hydroxide per
unit cell, which we call "monodispersed" crystals when
they are in a liquid carrier, meaning that they are
individual crystals of crystalline monolayer mixed metal
37~283A-F -4-
,
. .. ' ' ' -
'~:
~9~
hydroxides having crystal thicknesses in the range of
0.8 to 1.6 nm (8 to 16 A).
In the above formula, m is zero to 1, most
preferably 0.5 to 0.75, when not zero.
The D metal is Mg, Ca, Ba, Sr, Mn, Fe, Co, Ni,
Cu, or Zn, most preferably, Mg, Ca, or mixtures of
these, and the value of d is ~ero to 4, preferably 1 to
3 and most preferably 1, though m+d is not zero.
The T metal is Al, Ga, Cr, or Fe, preferably Al
and Fe, and most preferably Al.
The A anions are monovalent, divalent, trivalent
or polyvalent, and they can include inorganic ions such
as halide, sulfate, nitrate, phosphate, carbonate, most
preferably halide, sulfate, phosphate, or carbonate, or
they may be hydrophilic organic ions such as glycolate,
lignosulfonate, polycarboxylate, or polyacrylates.
These anions often are the same as the anions which form
part of the metal compound precursors from which these
novel crystals are formed.
An example of an alkoxide-based LMMH, such as one
shown in formula I, useful in the present invention may
be prepared by the following general chemical reaction:
(A) (Ml+X)(ocyH2y+l)x + (M2+Z~(ocnH2n+l)z + H2O =
Ml+XMz+Z(oH)x+z + CyH2yOH + CnH2nH
wherein:
Ml is a divalent metal cation, such as Mg;
M~ is a trivalent metal cation, such as Al;
37,283A-F -5-
y is from l to 4;
n is f~om l to 4;
and the amount of H2O is sufficient to provide
the requisite amount of OH- anions to satisfy the
requirements of the metal cations in the formula.
The reaction is relatively slow and the total
yield is limited by the extent of solubility of the
metal alkoxides in alcohol or other solvents in which
the reaction is carried out. As a general rule, a metal
alkoxide is most soluble in its corresponding alcohol.
However, solubility is only of the order of l percent by
weight in most cases with the notable exception of
magnesium ethoxide in ethanol.
At the outset, the preparation of the formula I
alkoxide-based LMMHs should be conducted in an
environment which is essentially free of water. Since
the beginning metal alkoxides are hygroscopic, and can
react to form hydroxide, carbonate and alcohol before
the LMMH has formed, it is sometimes necessary to
control local environment. Conse~uently, the use of
nitrogen-purged, moisture-free apparatus is recommended
during the initial mixing of the beginning metal
alkoxides.
In general, two metal alkoxides in powder form
are blended together and then added to dry alcohol in
3 the approximate weight ratio of alkoxide:alcohol of
l:50. This mixture is stirred while heating to 50C to
obtain a solution which may still contain some
undissolved solids. These solids may be separated by
vacuum filtration. The filtrate is then treated with
two drops (0.0~g) of deioni~ed water for each l g of
37,283A-F -6-
. .
i
.
2 ~
^ alkoxide while stirring. The filtrate obtained may be
allowed to stand for 1 hour to 48 hours. Forty to fifty
percent of the solvent is then evaporated, for instance,
by flowing nitrogen to produce an LMMH-containing gelO
In some instances a gel may form prior to the
evaporation step, in which case this step may be
eliminated.
In order to produce the more specific embodiment,
Mg~Aly(OHJzt the abo~e procedure may be followed. It is
preferred ~hat the magnesium and aluminum ethoxides be
combined in methanol.
Methods for preparing the LMMHs of formula II
above that are useful in the invention ERFs are
disclosed in EPO 0.207.811 to Burba, et al. The Burba
patent indicates that in order to produce a LMMH, a
mixture of the selected soluble metal compounds,
especially the acid salts (e.g. chloride, nitrate,
sulphate, phosphate, etc.) are dissolved in an aqueous
carrier. The ratios of the metal ions in the solution
are predetermined to give the ratios desired in the
final product. The concentration limit of the metal
compounds in the solution is governed, in part, by the
saturation concentration of the least soluble of the
metal compounds in the solution. Any non-dissolved
portions of the metal compounds may remain in the final
product as a separate phase, which is not a serious
problem, usually, if the concentration of such separate
3 phase is a relatively low amount in comparison to the
soluble portions, preferably not more than 20 percent of
the amount of soluble portions. The solution is then
mixed rapidly and intimately with an alkaline source of
OH- ions while substantially avoiding shearing agitation
thereby forming monodispersed crystals of LMMH. One
37,283A-F -7-
- . :
;:
. :
: -
-8-- 'i 2~9~9
. convenient way of achieving such mixing is by flowing
the diverse feed streams into a mixing tee from which
the mixture flows, carrying the reaction product,
including the monodispersed LMMHs of the above
formula I. The mixture may then be filtered, washed
with fresh water to remove extraneous soluble ions (such
as Na+ or NH~ ions, and other soluble ions) which are
not part of the desired product, and dried to remove
unbound water.
1 One method of preparing the formula II LMMH
composition, however not exclusively the only method, is
to react a solution of metal salts such as magnesium and
aluminum salts (approximately 0.25 molar) with an
appropriate base such as ammonia or sodium hydroxide in
quantities sufficient to precipitate the LMMH. For
ammonium hydroxide, the most preferable range is l to
l.5 equivalents of OH- per equivalent of salt anion.
The precipitation should be done with little or no shear
so that the resultant flocs are not destroyed. One
method of accomplishing this is to flow two streams, the
salt stream and the base stream, against one another so
that they impinge in a low shear, converging zone such
as would be found in a mixing tee. The reaction product
is then filtered and washed, producing a filtercake of
l0 percent solids and dried to remove unbound water.
LMMHs may be prepared to obtain a relatively
narrow distribution of particle sizes. It is believed
3 that this has significant consequences since the
electrorheological effect is believed to be proportional
to both surface charge and the surface to mass ratio or
aspect ratio. Consequently, high aspect ratios are
desirable and LMMHs have aspect ratios, generally
37,283A-F -8-
, :~ :- , - , -
9- ` 2~2~0~
ranging from 30 to 650, with_aspect ratios of 600 being
readily obtained.
The LMMH-based ERFs are characterized in that
they have little or no unbound or free water, preferably
no unbound or free water, are heat stable, require a low
concentration of the discrete phase, are responsive to
low applied field strengths and provide a strong
electrorheological response so that they may be usefully
employed in a variety of applications. It is believed
that ERFs which contain LMMH particles exhibit strong
electrorheological response because of the high surface
area per unit of mass of the particles which enables the
achievement of a high surface charge to mass ratio.
In EPO patent 0.207.811 the LMMHs are shown, for
example, as being prepared by mixing together the
requisite metal salts, such as MgCl2 and AlCl3, in the
desired ratio and then reacting the mixture with a
source on OH- ions, such as NH40H, in order to produce
monodispersed, monolayer crystals, each of which
contains both the metals as hydrated metal oxides.
There may be found in the crystals a very small amount
of the chloride ion due to incomplete conversion. In
more recent work with that type of reaction, mixtures of
metal alkoxides have been reacted with a source of OH-
ions to form the monolayer, monodispersed crystals of
mixed metal hydroxides in which there can be no residual
chlorine, since the beginning metal compounds did not
3 contain chlorine. Any of those LMMHs can be used in the
present invention, but those made from the compounds
free of halogens are preferred, especially due to the
possibliity that halide ions might tend to be corrosive
37,283A-F -9-
,:- ~ . . .
-~o 2~2~9
in some applications, especially if some ~ree (unbound)
water is permitted to enter the fluid.
The continuous phase of the ERF employing LMMH as
the discrete phase comprises a liquid, semi-solid or ~el
composition and may be selected from those dielectric
fluids having a relatively low dielectric constant of 40
to l, preferably less than 35 and most pre~erably less
than 5. These compositions include polyglycols,
alcohols, polyols, hydrocarbons, halogenated
hydrocarbons, mineral oils, silicone-based oils and
greases, ethers, ketones and the like in either liquid,
gel or semi-solid form. However, the continuous phase
is preferably selected from hydrocarbons or mineral oils
and is most preferably silicone-based oils. Operating
factors such as, for instance, operating temperature,
should be taken into account in selecting the continuous
phase composition to optimize the ERF composition for
particular applications.
As previously mentioned, the LMMH crystals are
positively charged and are consequently less readily
dispersed in non-polar than in polar fluids such as
alcohols. Thus, when the LMMH is to form the sole
component of the discrete phase, the choice of
continuous phase is restricted to those in which the
LMMH is dispersible up to the required weight
proportion. However, it is often desired to use as a
continuous phase a fluid in which the LMMH is not
3 readily dispersed. In this event, the LMMH may be
modified to render it more readily dispersible. The
modi~ication may be effected by treating the LMMH
crystals with a functionalizer, for example an aliphatic
carboxylic or fatty acid, such as, for instance, stearic
acid. Alternatively, steps may be taken to otherwise
37,283A-F -10-
- . ~
`
.~, ' .
-11- 2~2~9
neutralize the LMMH crystal'_ surface charge. Such
neutralization may be effected by combining the LMMH
with a dispersible negatively-charged functionalizing
species. For example, a synthetic clay such as
LAPONITE, containing no free moisture, may be combined
with an amine salt to form a composition that is readily
dispersible in mineral oil. This clay-amine composition
may then be combined with the LMMH crystals to form a
complex that is readily dispersed in non-polar fluids
thereby greatly expanding the range of fluids usable as
the continuous phase of the invention ERFs.
Furthermore, since these non-polar fluids are often the
most desirable continuous phase fluids because of their
low dielectric constants, the complexing or
functionalizing of the LMMHs allows the production of
ERFs having greater electrorheological response.
The discrete phase LMMH may be admixed with the
continuous phase in such quantity as will produce the
desired electrorheological response. These quantities
may usefully range from 0.05 percent by weight to 20
percent by weight based upon the weight of the ERF.
Preferably, the LMMH proportion should be in the range
from 0.l percent by weight to 5 percent by weight and
most preferably in the range from 0.5 percent by weiyht
to 2.0 percent by weight.
To produce the electrorheological effect, an
electric field is applied to the ERF. For a given ERF
3 composition, the electrorheological response is depen-
dent upon the strength of the applied field~ Clearly,
however, for ERFs containing different quantities of
LMMH or different LMMH compositions or having differing
continuous phases, the electrorheological response will
vary depending upon these factors. Thus, the selection
37,283A-F
12~
of an ERF for a particular application requires a selec-
tion of LMMH composition, continuous phase composition~
LMMH quantity, and electric field strength taking into
account environmental factors such as, for instance, the
temperature at which the ERF is expected to operate.
The use of aprotic c~atings on the LMMHs is
beneficial i~ the results obtained by the use of the
~MMH without the aprotic coating is not of the desired
magni tude .
The advantages of the invention LMMH-based E~s
may be more readily appreciated by reference to the non-
limiting~ illustrative examples shown hereinafter.
Discrete phases (other LMMHs) useful in the
present invention includes any of the particulate
compositions norrnally used in the formulation of ERFs
except that in this invention they are free of unbound
water. These include, for example, zeolites
(synthetic), naturally occurring clays such as, for
instance, montmorillonite, faujasite, chabazite and
their synthetic analogs. Other useful particulate
materials include silicates, alumina, polymers, such as,
for instance, polyacrylates, polyacrylake copolymers,
cellulose, starch and the like. The previous uses of
these materials as the discrete phase has also involved
free (unbound) water as an ingredient. In the present
invention, which uses the aprotic coating but not
unbound water, the ERFs can function at higher
temperatures than if water is required as an ingredient.
The present invention (ERFs) are free of unbound
water and include a discrete phase coated with a high
dielectric constant composition and a continuous phase
37,283A-F -12-
, . ' ~; ,:. ~ ~
-13- 2 ~
of a low dielectric constant, high dielectric strength
fluid. The coating composition is advantageously one
that will not boil o~f under normal conditions of use
(i.e., thus is called "heat-stable") but will ~orm an
aprotic layer around each particle of the discrete
phase. Thus, the coating composition enhances the
particle-particle interaction both in the presence and
in the absence of an electric ~ield. This enhancement
of particle-particle interaction is dramatically
illustrated by the ~ac~ that the addition of the high
dieleetric constan~ apr~tic comp~sition of the present
invention significantly increases the viscosity of the
ERF over that without the addition. The addition of the
high dielectric constant aprotic coatin~ also changes
the shape of the shear stress versus shear rate curve
for the ERF.
The ERFs of the present invention do not rely
upon adsorbed water to provide or produce the
electroheological effect and this contributes to their
thermal stability. Due to this thermal stability and
their powerful electrorheological response, the
invention ERFs may be used, for example, in the
automotive industry as clutch fluids in self-lubricating
clutch systems, as clutch fluids in continuously
variable transmissions and in shock absorbexs. The ERFs
may also find use in vibration or acoustic damping
systems to disrupt shock or noise harmonics by
continuously varying the "cushioning" properties
(viscosity) of the ERF by varying the strength of the
applied electric field. Thus, for example, the ERFs
could be used as shock dampening nuclear power plant
coolant pump mounts in nuclear submarines, shaft bearing
mounts for submarines to provide silent, vibration free
37,283A-F -13-
-14- 2 ~
rotation, absorptive coatings against active sonar,
active sound-absorbing partitions, building supports in
earthquake-prone areas, etc. The present novel ERFs may
also be usefull~ employed in cushions, mattresses and
seats to provide firmer or sof~er support as and where
needed by suitably a~ranging the applied field in grids
to achieve the desired end. Thus, the invention L~MH-
based E~Fs which combine thermal stability, low solids
concentration and strong electrorheological ~esponse are
useful in a wider range of applications than heretofore
possible with previously known ERFs.
The fluids useful as the continuous phase of the
present ERFs, using the above-described discrete
particles comprise fluids having a relatively low
dielectric constant and a high dielectric strength
including those which are known to be useful in so~e
prior art electrorheological fluids. These ~luids
include halocarbon oils, capacitor oils, silicon oils,
brake fluids, petroleum distillates, white oils and the
like.
The invention ERFs utilize any o~ a variety of
particles coated with a suitable aprotic high boiling,
relatively high dielectric constant fluid (hereinafter
"coating composition") which will not evaporate under
typical operating conditions. The coating compositions
of the invention form an electrolyte solution layer
analogous to the electric double layer. This coating of
3 an electrolyte solution layer on the particles is stable
through a range of temperatures thereby enhancing the
electrorheological effect. Further, the invention ERFs
show increased suspension stability in that the
37,283A-F -14-
2~2~
-15-
particulates are less inclined to settle out of ERF
mixture.
The dielectric aprotic coating compositions
useful in coating the particulates include relatively
high dielectric constant, high boiling point (greater
than 100 C) compositions such as alkylene carbonates,
for example ethylene and propylene carbonate, alkylene
sulfones, such as tetramethylene sulfone, ethers,
ketones, N-methyl pyrollidone and the like. It is
generally preferred that the coating composition have a
dielectric constant of greater than 35 and most
preferred that the composition have a dielectric
constant above 70 with a boiling point above 100C. The
coating composition is partly selected on 'che basis of
having a dielectric constant greater than that of the
continuous phase in which it is to be dispersed. If the
continuous phase has a dielectric constant as high as
35-40, then the aprotic coating is preferably one having
a dielectric constant of 70 or more to get a difference
of 30 or more.
The coating composition is added to the
particulates in sufficient quantity to form an
electrolyte solution layer on the particle surfaces. It
is difficult to quantify weight percent ranges for the
amount of coating composition to be added to the ERF,
considering the various surface areas and porosities of
the various particles one can use and also considering
3 the specific gravity of the various coating compositions
one can use. However, it is within the skill of
practitioners who, having read this disclosure, could
find the optimum weight percentages for the given
components and avoid putting too much or too little
coating composition in mixture. Too much aprotic
37,283A-F -15-
~2~09
-16-
coating composition can prod~ce too much conductivity ln
the ERF formulation; too little might leave some
particles insufficiently coated to achieve the optimum
results.
The ERF may be produced by mixing pre-coated
particles with the continuous phase fluid or it may be
produced by adding the partic~es to a mixture of the
continuous phase fluid and the aprotic coating
composition. Thus, the invention ERF, including coated
particles may be produced by any sequence of mixing
steps which allows the coating composition to ultimately
coat the surface of the particles. The particulate
content of the EPF 9 using particles other than LMMHs,
may vary from 5 to 70 percent by weight depending upon
the size and type of particulate, the continuous phase
fluid and the coating composition.
In the case of LMMH particulates, these
quantities may usefully range from 0.05 percent by
weight to 20 percent by weight based upon the weight of
the ERF. Preferably, the particle proportion should be
in the range from 0.5 percent by weight to 10 percent by
weight and most preferably in the range from 1.0 percent
by weight to 5 percent by weight.
Most prior art electrorheological fluid
formulations require a dispersant~ surfactant or
fluidizer to maintain the particulates of the discrete
phase in suspension. To the extent that such additives
are useful in the present invention, they may be added
without significant deleterious effect on the electrical
properties of the invention electrorheological fluid
compositions.
37,283A-F -16-
~17- 2~29~
The advantages of the_invention may be more
readily appreciated by reference to the following non-
limiting, illustrative examples.
The viscosities of the ERFs of the following
examples (except Example 10) were measured using an
apparatus which included a Brookfield Model LVF
viscometer, a stainless st,eel cylindrical eup and a
Canberra Model 3002 power supply. The posi~ lead o~
the power supply was co~nected to ~he steel cup. The
negative lead o~ ~hin steel wire rested upon ~he shaft
o~ the viscometer so as to provide continuous electrical
contact but not to significantly hinder the ro~ation of
the shaft. The viscometer spindle was located in the
center of the cup and was completely immersed in the
~luid being tested such that the distance from the
bottom of the spindle to the bottom of the cup was
greater than the distance from the spindle to the side
of the cup. The spindle was isolated from the
viscometer d~ive mechanism by a machined plastic sleeve.
The viscosities of the ERFs of Example 10 were
measured using an apparatus which included a Brookfield
Model LVF viscometer, a steel 177.5 ml juice can with
the inner epoxy lining removed and a Canberra Model 3002
power supply. The positive lead of the power supply was
connected to the steel can. The negative lead of soft
copper wire was wrapped around the shaft of the
viscometer so as to provide continuous electrical
3 contact but not to significantly hinder the rotation of
the shaft. The viscometer spindle was located in the
center of the can and was completely immersed in the
fluid being tested such that the distance from the
bottom of the spindle to the bottom of the can was
greater than the distance from the spindle to the side
37,283A-~ -17-
-18- 2~9~
of the can. The spindle was_isolated from the
viscometer drive mechanism by a latex rubber sleeve.
Example 1
A quantity of 3 Angstrom (A) mole sieve zeolite
of 3-5 micrometer (0.005-0.005 mm) particle si~e,
purchased from Aldrich Chemical Company, was dried by
heating overnight at 600C with a nitrogen purge. The
dried zeolite was then placed in a nitrogen purged glove
box where an ERF was prepared. Mineral oil (70 grams)
10 purchased from Aldrich Chemical Company was combined
with 30 grams o~ dried zeolite and the mixture was
stirred and shaken to promote homogeneity. The
electrorheological behavior for this sample was recorded
15 utilizing the previously described apparatus and the
data are reported in Figs. 1 and 2.
Example 2
A 75 gram mixture of ethylene carbonate and
20 mineral oil was heated to 60-70C in order to melt the
ethylene carbonate. The two components showed limited
miscibility. The ethylene carbonate and mineral oil
mixture was then mixed with zeolite which had been dried
as described in Example 1. The final composition had a
25 concentration of 15 percent by weight ethylene
carbonate, 30 percent by weight zeolite and 55 percent
by weight mineral oil and was very viscous. The
composition was diluted with the addition of mineral oil
at room temperature to a concentration of 16.83 percent
3 by weight zeolite. The diluted composition was stirred
and shaken to promote homogeneity. The composition was
then gently heated to 60C in order to completely
distribute the ethylene carbonate. The
electrorheological behavior of this sample is also
reported in Figs. 1 and 2.
37,283A-F -18-
,
~2~
-19-
Example 3
A quantity of DRYTECHTM fines (a polyacrylate
composition) obtained from The Dow Chemical Company was
placed in a ni~rogen purged glove box. The DRYTECHTM
~ines were sieved in the glove box and those particles
smaller than 2~2 microns (0.212 mm) collected and stored
in the glove box. No further pretreatment of the
D~YTECHTM fines was undertaken. An ERF was prepared in
the nitrogen purged glove box by combining 70 grams of
mineral oil, purchased from Aldrich Chemical Co.with 30
grams of the DRYTECHrM fines and the mixture was stirred
and shaken to promote homogeneity. The electrorheolo-
gical behavior of this sample and similarly prepared
samples containing 20 and 40 percent by weight DRYTECHTM
polyacrylate in mineral oil are reported in Figs. 3 and
4.
Ethylene carbonate (5 grams) was added to 65 gms
of mineral oil and the mixture heated to 60~70 C in
order to melt the ethylene carbonate. The ethylene
carbonate and mineral oil mixture was then mixed with 30
gms of DRYTECHTMfines which had been sieved as described
above. The final suspension had a concentration of 5
percent by weight ethylene carbonate, 30 percent by
weight DRYTECHTMfines, and 65 percent by weight mineral
oil. The suspension was stirred and shaken to promote
homogeneity and finally gently heated at 60C in order
to completely distribute the ethylene carbonate. The
electrorheological behavior of this sample is also
reported in Figs. 3 and 4.
Example 5
A quantity of EF 101 FiberfraxTMfiber
(aluminosilicate fiber) obtained from Standard Oil
37,283A-F -19-
2~2~9
-20-
- Engineered Materials was dried at 120C in an oven
overnight. The dried material was then placed in a
nitrogen purged glove box where the ERF was prepared by
combining 95 grams o~ mineral with 5 grams of EF 101
FiberfraxTMfiber. The mixture was stirred and shaken to
promote homogeneity. The electrorheological behavior o~
this sample is reported in Figs. 5 and 6.
EXAMPLE 6
Ethylene carbonate (0.34 grams~ was added to
94.66 grams of mineral oil and the mixture heated to 60-
70C in order to melt the ethylene carbonate. The
ethylene carbonate and mineral oil mixture was then
mixed with 5 grams of EF 101 FiberfraxTMfiber. The
composition had a concentration of 5 percent by weight
EF 101 FiberfraxTMfiber, 0.34 percent by weight ethylene
carbonate and 94.66 percent by weight mineral oil. The
composition was stirred and shaken to promote
homogeneity and finally gently heated at 60C in order
to completely distribute the ethylene carbonate. The
electrorheological behavior of this sample is also
reported in Figs. 5 and 6.
EXAMPLE 7
A quantity of DRYTECHTMfines obtained from The
Dow Chemical Company was placed in a nitrogen purged
glove box. The DRYTECHTMfines were sieved in the glove
box and the particles smaller than 212 microns (fines)
collected and dried at 50 degrees centigrade for 4 hours
3 under 30 in. (762 mm)Hg vacuum. The dried DRYTECHTM
fines were then placed back in the glove box where the
E~F was prepared by combining 70 grams of mineral oil
with 30 grams of dried DRYTECHTMfines. The mixture was
stirred and shaken to promote homogeneity. The shear
37,283A-F -20-
.
- - ~
~2~9
-21- -
-- stress versus shear rate electrorheological behavior of
this sample is reported in Fig. 7.
Separately, 65 grams of mineral oil was combined
with 5 grams of ethylene carbonate and the mixture
heated to 60-70~C in order to melt the ethylene carbon-
ate. The ethylene carbonate and mineral oil mixture was
then mixed with 30 grams of dried DRYTEC~TM fines. The
composition was stirred and shaken to promote homogene-
ity and was noticeably more viscous than the fluid
prepared in Example 4. The composition was then gently
heated to 60C in order to completely distribute the
ethylene carbonate. The final composition had a concen-
tration of 30 percent by weight DRYTECHTMfines~ 5
percent by weight (0.057 moles) ethylene carbonate and
65 percent by weight mineral oil. The shear stress
versus shear rate electrorheological behavior of this
sample is reported in Fig. 8. Note that the viscometer
used could not read beyond 700 dynes/cm2 (0.007
newton/cm2); consequently, readings recorded as "700
dynes/cm2" could be substantially higher.
E~AMPLE 8
Mineral oil (63.2 grams) was combined with 6.8
grams of tetramethylene sulfone (TMS) and the mixture
heated to 60-70C in order to melt the TMS. The TMS and
mineral oil mixture was then mixed with 30 grams of
dried DRYTECHTM. The composition was stirred and shaken
to promote homogeneity and was noticeably more viscous
3 than the ~luid prepared in Example 4. The composition
was then gently heated to 60C in order to ccmpletely
distribute the TMS. The final composition had a
concentration of 30 percent by weight DRYTECHTMfines,
608 percent by weight (0.057 moles) TMS and 63.2 percent
by weight mineral oil. The shear stress versus shear
37,283A-F -21-
.
:: `
,
-22- ~29~
- rate electrorheological beha~ior of this sample is
reported in ~ig. 9.
E~AMPLE 9
The compositions used in Examples 1 (without
ethylene carbonate) and 2 (with ethylene carbonate) were
allowed to remain undisturbed in capped glass bottles,
6.~ cm in height, at room temperature ~or a period of 48
hours. The compositions separated into two phases. In
the composition not containing ethylene carbonate, the
top layer was clear mineral oil while the bottom layer
was cloudy and contained the zeolite particles. The
composition containing the ethylene carbonate separated
to a lesser extent than the other. The clear (mineral
oil) layer in the ethylene carbonate composition was
only 1.47 cm thick while the same layer in the
composition which did not contain any ethylene carbonate
was 2.54 cm thick. This indicates that the ethylene
carbonate-containing composi~ion is more stable and
settles to a lesser degree than the composition not
containing ethylene carbonate.
EXAMPLE 10
An alkoxide gel was prepared by mixing magnesium
ethoxide and aluminum ethoxide in dry methanol under
moisture free conditions with subsequent water addition
to produce an alkoxide-based LMME gel. This provided a
Mg1 7Alo 5(0E)5 compound, as described before, which was
relatively viscous at room temperature even though the
3 concentration of the LMMH was only 1 percent by weight.
An ERF was prepared by admixing 45.06 g of this
alkoxide LMMH gel containing 1 percent LMMH with
37,283~-F -22-
~2~
-23-
138.89 g of anhydrous methanQl. This produced a
composition containing 0.45 g LMMH or 2450 ppmw.
The composition was placed in the apparatus
described above and the viscosity measured at field
strengths of 0, 10, 100 150, and 200 applied volts. Ten
measurements were taken at each voltage level with a 20
second interval between measurements. Upon stepping up
the field strength, the voltage and viscosity were
allowed to equilibrate for 2-3 minutes before readings
were taken at approximately 20 second intervals. To
test the effect of current direction, the polarity was
reversed at the 10 volt level. This reversal produced
no significant change in the measured viscosity. The
results are shown in Figure 10.
EXAMP~E 11
A solution containing 3.0 g (0.004 moles) of the
chloride salt of a monoquaternary amine (ARQUADTM 2HT-
75~ Akzo Chemie America, 75 percent active) was preparedby dissolving the salt in a mixture of water (9 g),
methanol (5 g), and isopropanol (4 g). A synthetic
clay, LAPONITE RDSTM (Laporte Industries Ltd.) which
contains 6.0 percent pyrophosphate was then added to the
amine solution and the resulting mixture was blended
under high shear. The solvent was then removed by
vacuum and residual solids were filtered and washed with
distilled water. The washed solids (4.7 g) were dried
and then mixed into mineral oil (55.4 g) at high shear
3 for two minutes and thereafter shaken for 30 minutes.
Upon testing this mixture, which contained 7.8 percent
by weight solids based on the total weight of solids and
oils, in an electric field, it showed no
37,283A F -23~
2 ~ 9
-24-
- electrorheological response Qver the field strengths
examined.
The LAPONITE-amine-mineral oil mixture (60.1 g)
was then blended at high shear with 50 9 of MgxAly(OH)z
LMMH gel (1.35 percent by weight LMMH in methanol) to
produce a milky fluid. The milky fluid was subjected to
evaporation to remove the methanol. This resulted in a
yellow, low viscosity mixture. The electrorheological
response of this mixture at shear rates of 0.105 sec-
and 21 sec-l is shown in Figure ll.
EXAMPLE 12
A clear solution containing 2.5 g (0~0088 moles)
of stearic acid in acetone (40 g) was prepared. To this
solution was added 90.1 g of LMMH gel (1.33 percent by
weight LMMH in methanol) and the resultant mixture was
thoroughly agitated. The solvents were then removed by
vacuum and 3.91 g of white solids were recovered. The
solids were dried at 120C for one hour yielding 3.66 g
of dry white solids. After grinding, 3.4 g of solids
were recovered, added to 56.6 g of mineral oil and
blended under high shear for two minutes. Some solids
were observed to settle out after 30 minutes. The
electrorheologi-cal response of this mixture at shear
rates of 0~105 sec-l and 21 sec-l is shown in Figure 12.
EXAMPLE 13 (for comparison with Examples 11, 12, & 14)
A solution of 5.12 g of (0.10 moles) of LAPONITE
RDSTM in 100 cc of deionized water was prepared. A
second solution was prepared containing 7.5 9 (0.010
moles) of 75 percent active ARQUADTM 2HT-75 dissolved in
400 g of isopropanol. These two solutions were mixed
together and the solvents removed by vacuum to recover
11.15 g of solids. The recovered solids were dried at
37,283A-F -24-
-25~ 29~
~- 120C for 30 minutes and grou~d. The ground solids were
then washed with one liter of deionized water and again
dried at 120C for one hour yielding 10.4 g of white
powder. The powder was dissolved in an isopropanol (400
g)-water (50 g) mixture to which 52 g of mineral oil
were added. Removal of the solvent resulted in the
formation of 61.37 g of an almost-clear, thick, creamy
gel. An additional 152 g of mineral oil was added to
reduce the sample viscosity so that electrorheological
readings could be taken. The final product contained
2.3 percent by weigh~ LAPONITE RDS, 2.54 percent by
weight ARQUADTM 2HT-75, and 95.15 percent by weight
mineral oil, based upon the total product weight. The
electrorheological response of this product at shear
rates of 0.105 sec-l and 21 sec-l is shown in Figure 13.
EXAMPLE 14
A mixture was prepared by adding 58.3 g (0.005
moles) of LMMH gel (1.17 percent by weight LMMH in
methanol) to 58 g of mineral oil. The mixture was
blended for 30 minutes under high shear. To this
mixture, with stirring, was added 1.42 g (0.005 moles)
of stearic acid dissolved in methanol. The solvent was
removed under vacuum resulting in 58.9 g of clear, thick
gel being recovered. An additional 60.0 g of oil was
added and the mixture blended at high shear for two
minutes in order to reduce the viscosity enough for the
ER response to be measured. The final composition of
the sample was 0.57 percent LMMH, 1.18 percent by weight
stearic acid, 9~.25 percent by weight mineral oil. The
electro-rheological response at shear rates of 0.105
sec-l and 21 sec-l is shown in Figure 14.
37,283A-F -25-
,
-26- I' 2~29~9
- The results demonstrate that LMMH with stearic
acid (Examples 12 and 14) has a better
electrorheological response than LAPONITETM(s) and
ARQUADTM 2HT-75 (Example 13) but not as good as the
response of LMMH with LAPONITETM and ARQUADTM 2HT-75
(Example 11).
: 25
: : :
3o
37,283A-F -26-
~ '
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: .
