Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
` - 1148708
BACI~G~OUND OF TIIE INVENTION
Organic friction material compositions currently used
in clutch and brake linings of vehicles must be capable of
withstanding the severe operating temperatures and dynamic
. pressures experienced during repeated applications. To pre-
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vent a deterioration in performance and physical degradation
during such applications, the linings are normally reinforced
by asbestos fibers randomly dispersed throughout a resin
matrix. However, recent medical evidence indicates that
asbestos fibers can cause health hazards for people exposed
thereto during the manufacture of clutch and brake linings.
Unfortunately, because of the presence of fine diameter
asbestos fiber during the manufacture of brake lining using
asbestos fiber, a portion of the asbestos often becomes air-
borne in quantities that exceed the exposure standard of
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asbestos fiber in the United States as controlled by the
- Occupational Safety and Health Act of 1970. Furthermore,
mechanics relining the automotive brakes are also exposed to
some quantity of asbestos from the linings.
In an effort to reduce the environmental contamination
by the asbestos fiber and thereby continue the manufacturing of
asbestos based organic friction linings, a water slurry process
disclosed in Canadian Patent No. 1,105,214 (issued July 21,
1981) has been evaluated. The water slurry can be transmitted
throughout a manufacturing facility without contaminating the
surrounding environment with asbestos fibers. However, before the friction
ma~erial can be cured, the water in the slurry must be removed in order to
be assured that any resulting lining has essentially the same operating
characteristics as a lining made from a dry mix. Unfortunately, this
process adds considerable cost to the manufacturing cost of a brake or
c~utch lining, and does not ~ecessarily solve emission problems during
finishing and inspection.
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~1~8708
` In a effort to use readily available materials and the san~
manufacturing facilities, as currently available, it has been suggested
that glass and/or mineral fibers be used in place of at least a portion of
the asbestos fillers. U.S. Patent 3,967,037 discloses several lining con-
positions utilizing glass fiber in place of asbestos. Fr~n experimentation,
it has been determined such lining compositions in normal operational
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conditions produce brake noise, severe rotor scoring and wear, and poor
frlction material life when the lining is mated with a cast-iron rotor or
- drum.
In an effort to stabilize the coefficient of friction while
reducing both sooring and wear on a corresponding cast iron drum or rotor,
Canadian Patent Application 328,221, filed May 24, 1979, discloses a
c~nposition of material for a friction lining having carbon and/or graphite
particles therein which modify any detrimental effects that glass fibers in
a composition of materials may have on a corresponding mating surface.
SUMMARY OF T~E INVE~C~
We have discovered that the detrimental effects caused by glass
fibers in a friction material can be reduced by the separation of the
individual bundles of glass fibers in the process of manufacturing the
friction material.
In this process, dry ingredients including a thermosetting phenolic
resin, friction modifiers and glass fibers are mixed together to form a
oomposition of materials. me composition of materials is blended until a
bulk density of between 0.1 -0.6 gm/cc is achieved through the separation
of the individual filaments that make up the glass fibers. me blended
composition of material is thereafter formed into briquettes. me briquettes
t are hot pressed to a predetermuned density and shape. mereafter the pre-
fo~med briquettes are cured in an oven to set the phenolic resin and hold
; the filaments and friction modifiers in a fixed position. The cured
briq~lettes are thereafter ground to a desired thickness to produce a friction
~terial.
It is an object of this invention to provide a method of
manufacturing
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a friction material from a composition of materials including glass fibers
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` wherein the individual filaments are separated and thereafter uniformly
distributed throughout the composition of materials.
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It is a further object of this invention to modify the bulk density
~; of a composition of material during processing through the separation of
glass fibers in a blending process.
It is another object of this invention to provide a composition,~
of material for use as a friction material with filaments from glass fibers
~ to establish a substantially uniform coefficient of friction between 25~-65~ F.
'~ 10 These and other objects should be apparent from reading this
specification while viewing the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a table showing the components incorporated into the
composition of material for making a friction lining according to the principlesof this invention;
Figure 2 is a graph comparing friction versus temperature of a typical
asbestos based friction material and glass f;ber based friction materials;
Figure 3 is a graph comparing wear versus temperature of a typ;cal
asbestos based friction material and glass based friction materials;
,~ 20 Figure 4 is a table showing friction stability, friction level, pad
and rotor wear of a typical asbestos based friction material and glass based
friction materials;
Figure 5 is a graph showing the fade and recovery of a typical
asbestos based friction material and glass fiber based friction materials;
Figure 6 is a table comparing vehicle test data of a typical asbestos
based friction material and glass fiber based friction materials;
~-~ Figure 7 is a graph illustrating pad and rotor wear of a test vehicle
associated with a typical asbestos based friction material and glass fiber
based friction materials;
Figura 8 is a photograph showing the effect of various blending times
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on ~lass fiber;
Figure 9 is a photomicrograph magnified 20 times
; showing a glass fiber before and after blending for 10
minutes;
- F1gure 10 is a graph comparing friction versus
temperature of glass fiber based friction materials made
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according to the principles of this invention; and
Figure 11 is a graph comparinq wear versus
temperature of glass fiber based friction materials made
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according to the principles of this invention.
- Figures 10 and 11 are found on the third page of
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drawings along with Figure 7.
DETAILED DESCRIPTION OF TIIE INVENTION
1 , .
In order to evaluate the friction material disclosed
by this invention, a typical asbestos friction material A
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disclosed in Figure 1, was formulated and characterized to
: - establish a standard or base for illustratinq an acceptable
`~ coefficient of friction and rate of wear for a brake lining
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~j of an automobile. Figure 1 also illustrates the modifi-
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ri~J 20 cations associated with the composition of materials made
` according to this invention.
The ingredients in the composition of material A
were processed into brake friction material in the
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~; following manner.
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Asbestos fiber, zinc powder, organic modifiers
(two parts of cashew nut powder and one part rubber scrap),
; inorganic modifier ~barytes), and dry phenolic resin in the
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weight percentages shown in Figure 1 were dry mixed
: together for about 30 minutes until a homogenous mixture was
-` 30 created. Thereafter, this homogenous mixture was placed in
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`.`! a mold and compacted into briquettes. The briquettes were
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! then transferred to a press station and individually com-
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: pressed at about 6,000 pounds per square inch to establish
i. a predetermined shape and density, while the temperature of
the briquette was raised to about 275F. The 275F
temperature caused the phenolic resin to flow throughout the
~ mixture and establish a matrix for holding the other
,~ ingredients in a fixed position. Thereafter, the
' briquette as transferred to a curing oven having a temperature
.
. of about 500F to further
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set the phenolic resin. The rubbing surface of the cured briquette was
then ground to a spe~ific size corresponding to a brake pad. Thereafter, a
portion of the pad was tested on a Chase-type sample dynamometer. This test
` consists in making 40 applications of 20 second duration with a l-inch
square sample of friction material against a cast-iron drum rotating at
~25 rpm (40 mph). After a burnish sequence, tests are made at 250 F, 350F,
450 F, 550F, 650 F, and 250 F (re-run). The controlled output torque was
held at 350 in-lbs for the tests.
The sample dynamometer data in Figure 2 gives the 250 F, 350 F,
450 F, 550F and 650 F steady state friction ievels and the data in Figure 3
gives the 250 F, 350 F, 450 F, 550 F and 650F wear values.
~he coefficient of friction of composition A was measured and
indicated as curve 100 in Figure 2 while the wear of the brake pads experienced
at the various temperatures was calculated and illustrated by curve 102 in
Figure 3. It should be noted that the wear rate of composition A is acceptable
below 350 F. However, when vehicles equ;pped with such brakes are repeatedly
applied, the thermal energy generated rapidly increases above 450 F where the
wear rate reaches an undesirable level.
Because of the stopping requTrement standards established by the
Department of Transportation in FMVSS 105-75, the maximum operating temperature
generated in bringing a vehicle to a stop during repeated panic stop conditions
often reaches 450F. Thus, typical standard asbestos organic friction lin;ngs,
while producing acceptable coefficients of friction, are damaged since the
wear rate increases exponentially above 350 F as shown in F;gure 3.
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- A brake pad of composition A was mated with a caltper and rotor
assembly of a full brake and installed on an inertial dynamoMeter. The
inertial dynamometer procedure combined performance and wear versus temperature
testing with emphasis placed on friction change wtth Increased duty usage.
The test procedure Included the following: pre-burnish effectiveness checks
(at 30, 60, and 80 mph with 0.4, 0.6, and 0.7G deceleration, respectively)
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with an initial pad temperature of 200F; 200 burnish stops (40 mph at 12
ft/sec. from 250F initial pad temperature); post-burnish effPctiveness (at
30, 60 and 80 mph with 0.4, 0.6 and 0.7G deceleration, respectively) followed
by 3 SAE-type fade and recovery checks to 450 , 600 and 700 F, and a ftnal
effectiveness check (at 30, 60 and ~0 mph with 0.4, o.6 and 0.7G deceleration).
The friction level and friction stability of composition A
as indicated by line pressure required to make 3 successive stops from 60 mph
at 0.7G deceleration is shown by the table in Figure 4. The pad and rotor
wear data are also included.
The fade characteristics of composition A is shown by lines lOô,
110, and 112 and the recovery characteristics is shown by lines 114, 116 and
118 in Figure 5.
Because of the superior frictional characteristics and high tensile
strength of glass fibers over other fiberous materials suitable for friction
materials, it was decided to modify composition A through the substitution of
glass fiber and metal oxide particles to produce a glass fiber based
composition of material B shown in Figure 1.
The glass fiber which is known in the industry as Type E is made
by heating raw materials, such as s;lica sand, ltmestone, dolomite, clay, boric
acid, soda ash and other minor ingredients in a h;gh-temperature furnace in a
direct melt process to produce glass. The glass flows to forehearths in the
bottom of the tank furnace. The glass flows through numerous holes or orifices
located in platinum alloy bushings or spinnerettes to produce filaments of molten
glass. The filaments, which can range in number from 20 to 2,000, are gathered
together as a thread or strand and attached to a rotating drum which turns a.
a speed up to 75,000 rpm to produce a glass fiber. Thereafter, the glass
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;~; fiber is treated with a silanizing or sizing agent, such as a silane, to
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~`~ improve the resin-to-fiber adhesion. Thereafter, the continuous fiber is cut
into lengths which may vary from 250-10,000 microns.
3 The composition of ma~erial ~ shown in Fisure 1 was compounded in
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the same manner as composition A and processed into a brake pad. The bra~e pad
of composition B was installed in the Chase-type sample aynamometer and a
friction wear test was performed. The coefficient of friction of composition
B is illustrated by curve 104 in Figure 2 and the wear rate by curve lOS
in Figure 3. As shown in Figure 2 the coefficient of friction of composition
B is substantially equivalent to ~he coefficient of friction of composition A.
However, the wear rate as shown in Figure 3 is unacceptable for use as a
friction material.
Since the coefficient of friction as shown in Figure 2 of composition
C is substantially stable above 450 F, it was decided to evaluate the
modifications for composition B which would reduce the wear rate. Thus,
it was decided to remove the abrasive metal oxide particles through a
substitution of cashew nut dust particles and a non-abrasive mineral particle
(barytes) to the mixture to produce composition C shown in Figure 1.
The processed mineral fiber in composition C is made up of a composi~ion
consisting of silica, alumina, calcia, magnesia and other oxides. The fiber
diameters may vary from 1-15 microns and the fiber lengths may vary from
40-1,000 microns. During the manufacture of these fibers, the surface thereof
is treated with a silanizing agent to improve the resin-to-fiber adheston.
The composition of material C was compounded and processed into
disc brake pads. The wear and friction level as measured on the inertial
dynamometer of composition C is shown in Figure 4. The fade characteristics
; of composition C are illustrated by curves 120, 122 and 124 while the
recovery characteristics are illustrated by curves 126, 128 and 130 in
; Figure 5. From comparing the friction and wear data of composition C with
composition A, it is apparent that composition C is superior to composition A.
Thereafter, a test vehicle was equipped with friction material pads
made of compositions A and C and test data obtained therefrom to further
evaluate the glass fiber composition C. The test vehicle was a station
wagon having a weight of 5,C00 lbs.GVW. Except for burni,h, reburnish and
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light/heavy duty cycle operations, the performance data was obtained with
only the front di;c brakes functioning. Noise rating was determined with
` light brake applications (20-150 psi line pressure) at slow speed (5-30- mph) in a quiet area (such as an inactive parking structure) for the best
noise amplification and detection. In each noise search, the windows were
open and the radio and heat/air conditioner fan were turned off to provide
a low noise background.
The performance data of composition C and that of composition A is
presented in Figure 6. The first four sets of effectiveness data were obtained
with an initial pad temperature at 150F before each brake application.
Applications were made at 10, 30 and 60 mph, with 10 or 15 ft/sec.2 decelerationas specified. The fifth effectiveness data were obtained in the same manner,
except that the initial pad temperature was kept at 300F. The first effective-
ness test measures the effective line pressures at various speeds before the
pads were subject to burnish; the second, post burnish and before the fades;
the third, post 450F and 600F fades; the fourth, post 700 F fade.
It is clear from the data in Figure 6 that compositions C and A
have comparable friction levels at the start of the test. However, the
asbestos-free composition C has better friction stability than the typical
asbestos based composition A as indicated by the smaller frictional level
change and by the lack of friction increase with use which leads to brake
burnup and friction instability.
After the series of tests reported in the table of Figure 6, the
pads and rotors were measured for wear. The right front pad and rotor
wear and the left front pad and rotor wear for compositions A and C are
illustrated by lines RF and LF, respectively in Figure 7. From viewing
Figure 7 it should be evident that the pad wear resistance of composition
C is clearly superior to composition A. The rotor wears of the A and C
are comparable (0.0000 and 0~0001 inches, respectively~.
3 ~n order to further evaluate the family of composition of materials
that include glass fiber as the strengthening ngredient, composition C was
modified by removing the carbon particles and reducing the phenolic resin
content while increasing the glass fiber and mineral fiber to produce composi-
` tion D shown in Figure 1.
The friction and wear data of composition D generated from theChase-type sample dynamometer are shown by curves 105 and 107 in Figures 2
and 3, respectively.
The results of the inertial dynamometer test of composition D are
i shown in Figure 4.
Thereafter, composition D was procéssed into brake pads and
placed on the test vehicle. The results of the vehicle brake test for
, . .
composition D are illustrated in Figure 6. When the data shown in the
-~` table of Figure 6 is compared, it is evident that the glass flber reinforce-
ment and cashew nut powder friction dust mod;fied compositions of both
compositions C and D have better friction stability and less pad wear than
- composition A.
In attempting to duplicate the data for compos;tion D sho~n in the
table of Figure 6, different data values were obtained using the same
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weight percentages for the material shown in Figure I for composition of
material D. In attempting to explain the different data generation with
~,
~ the same material, it was determined that slight variations could occur in
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the blending of the dry ingredients from one batch to another. On in-
vestigation it was observed that the bulk dens;ty of the compositlon varied
with increased blending time. This change in bulk density was attributed to the
~ separation of the filaments that made up the glass fibers.
- To evaluate the effect of the glass fibers on blendtng time, six
samples of glass fibers each weighing 10 grams were evaluated. Five samples
~; were successively placed in a mixer and hlended for times varying from I m;nJt2
to 10 minutes. The five samples after blending were removed from the mixer
and placed in piles adjacer.t the test sample designated XF-10 as shown by the
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photograph in Figure 8. As shown in Figure 8, the glass fibers expanded by
separation in almost a direct proportion to the blending time in the mixer.
To substantiate the speculation that substantially the entire bundles
of filaments that make up glass fiber separated, SEM photo micrographs (20 x)
shown in Figure 9 were taken of the glass fiber in sample XF-I0 and the glass
`~ fiber after 10 minutes of blending. As shown in Figure 9, the individual
filaments after blending are randomly dispersed without any definite orientation
as compared to the tight knit bundles of the glass fiber in the original
material.
To determine the optimum effect of`the expansion or opening of the
bundles of filaments of glass fiber on a friction lining, a series of tests were
performed on composition D made by a process of manufacturing wherein the blending
times were varied. In the first composition designated D-l, the dry ingredients
were placed in a mixer and blended for a time period of 5 minutes. At the
end of 5 minutes, the composition of material had a bulk dens;ty of about
-3
0.46 gm/cc . The material was transferred to a briquette mold and brjquettes
` were made from composition D-l. These individual briquettes were transported
; to a press and compacted with a force of about 6000 psi to a predetermined
density while at the same time the temperature was raised to 275 F to allow
the phenolic resin to flow throughout the mixture and hold the other ingredients
in a fixed position. Thereafter, the indtvidual briquettes were transterred
to a curing oven having a temperature of about 500 F to set the phenol;c
resin. The individual briquettes of composition D-l were ground to a specific
size brake pad and thereafter when tested by the Chase-type sample dynamometer
,'~J, procedure described above with respect to composition A produced a coefficient
of friction illustrated by line 130 in Figure 10 and a wear rate illustrated
by line 132 in Figure 11.
` Thereafter, a second composition designated D-2 ~as placed in a mixer
and blended for a time period of 10 minutes. At the end of lD minutes,
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composition D-2 had a bulk density of about 0.25 gm/cc . This blended material
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was processed into brake pads in the same manner as composi.ion D-l and when
tested on the Chase-type sample dynamometer produced a coefficient of friction
illustrated by line 134 in Figure 10 and a wear rate illustrated by line 136
in Figure 11.
~` A third composition designated D-3 was placed in a mixer and blended
` for a time period of 15 minutes. At the end of 15 minutes, composition D-3
had a bulk density of about 0.20 gm/cc 3. This blended material was similarly
. =, , .
processed into brake pads and when tested on the Chase-type sample dynamometer
produced a coefficient of friction illustrated by line 138 in Figure 10
; ~. ...
and a wear rate illustrated by line 140 in Figure 11.
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From the test data generated by compositions D-l, D-2 and D-3,
~-~; it was discovered that a coefficient of friction for friction lining
utilizing glass fiber is enhanced wilen the blending time in the manufacturing
~` process is limited to between 5-15 minutes.
~` in order to ;nsure that the tngredients are uniformly distributed
throughout the resulting brake pad, it was decided to pre-blend 'he ingredients
prior to adding the glass fibers to the mixture.
~; Therefore, the friction modifiers and phenolic resln ~ere placed in a
. .,
~ mixer and pre-blended for 5 minutes before the glass fibers in composition D
- i
2~ were added to produce a composition designated as D-4. This composition D-4 was
~, further blended for 5 minutes to expand or separate the filaments ;n the glass
fiber. At the end of this time period (5 minutes pre-blend and 5 minutes blend
with glass fiber) composition D-4 had a bulk density of about 0.45 gm/cc
~ Thereafter, when composition D-4 was processed into a brake pad and tested on
Y~ the Chase-type sample dynamometer, a coefficient of friction illustrated by
line 142 in Figure 10 was produced and a wear rate illustrated by line 144
in Figure 1} was achieved.
;` A fifth composition designated D-5 ~as produced by pre-blending th3
~` friction modifiers and resin for 5 ~inutes before adding the glass fiber and
thereafter blending the composition for an additional 10 minutes for a total
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blend time of 15 minwtes. At the end of 15 minutes, composition D-5 had a
bulk density of about 0.26 gm/cc 3. Thereafter, composition D-5 was processed
into a brake pad and tested on the Chase-type sample dynamometer. Composition
~- D-5 produced a coefficient of friction illustrated by line 146 in Figure 10
and a wear rate illustrated by line 148 in Figure 11.
A sixth composition designated D-6 was produced by pre-blending the
friction modifiers and phenolic resin for 5 minutes before adding the glass
fiber. Thereafter, this mixture was blendèd for another 15 minutes for a
total blend time of 20 minutes to produce a bulk density about 0.21 gm/cc 3.
Thereafter, composition D-6 was processed into a brake pad and when tested on the
Chase-type sample dynamometer produced a coefficient of friction illustrated by
line 150 in Figure 10 and a wear rate illustrated by line 152 in Figure 11.
,. ~
~ To substantiate the finding with respect to the expansion of the
: . .
`~ individual filaments that make up the stands of glass ftber, a seventh
,
composition designated D-7 was made wherein a glass fiber identified as
type E OCF405-AA-.13" was substituted for the original glass fiber OCF497-BB-.13".
The configuration of glass fibers in OCF405-M-.13" is the same as OCF497-B3-.13"
-, with the exception of the silanizing agent used as sizing for the bundle of
filaments. The friction modifiers and phenolic res;n tn compositton D-7 were
~ 20 pre-blended for 5 minutes before the glass ftbers were added. Th;s mtxture
:~ was blended for an additional 15 minutes for a total blend ttme of 20
minutes to produce a bulk density ;n the mixture of about 0.54 gm/cc 3.
Thereafter, this blended mixture was processed into a brake pad and tested
on the Chase-type sample dynamometer. Composition D-7 when tested produced 3
coefficient of friction illustrated by line 154 in Figure 10 and a wear
rate illustrated by line 156 tn Figure 11.
Another glass fiber identified as type E OCF636-DE-.13" was
substi.uted for the glass fiber in composttton D to produce another composition
!''. identified as composition D-8. This glass fiber has a d;ameter of approximately
3 6 microns. The friction modifiers and phenolic resin in composition D-8
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~` were pre-blended for 5 minutes and the glass fiber OCF636-DE-.13" added and
this mixture blended for another 15 minutes for a total blend time of 20 minutes.
; Composition D-8 had a bulk fiber density after 20 minutes of blending of about
0.07 gm~cc . Thereafter, composition D-8 was processed into a brake pad and
when tested on the Chase-type sample dynamometer, produced a coefficient
of friction illustrated by line 158 in Figure 10 and a wear rate illustrated
by line 160 in Figure 11.
. In establishing the ranges for the ingredients in the family of glass
fiber friction linings, the glass fiber in composition D was reduced and replaced
by mineral fiber and an increase in the cashéw nut powder to produce composition E
~~ shown in Figure 1. Composition E was blended for a time period of about 5
ri minutes and thereafter processed into brake pads. When composition E was
tested on the Chase-type sample dynamometer a coefficient of friction
illustrated by line 170 and a wear rate illustrated by line 172 were produced.
Both friction and wear of composition E are acceptable.
-` To further substantiate our discovery that the opening of the glass
fiber bundles stabilizes the coefficient of brake pads reinforced with glass
fibers while proviting an acceptable wear rate, low noise and compatibility with
a cast iron rotor or brake drum, composition D was further evaluated through
-: 20 a vehicle test. A composition designated C 0005-1 was produced by pre-blending
~ the friction modifiers and phenolic res;n of compos;t;on D for 5 m;nutes before
, . .
~ adding the glass f;bers and further blending for an additional 2 m;nutes.
~,
Composit;on C 0005-1 was processed ;nto brake pads and installed on a
veh;cle. The veh;cle was dr;ven 2,586 m;les in all kinds of traffic on
the streets of Detroit, Michigan. Thereafter, the disc pads were evaluated.
The disc pads on the front axle of the vehicle had the following average pad
wear: left front - ;nner 0.095 inches and outer û.078 inches; and rignt
front - inner 0.099 inches and outer 0.061 inches. Both the left and right
rotors had a maximum wear of 0.007 inches, which is considered unacceptable.
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~ 3 During the road evaluation of composition C 0005-1 it was observed, noise
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was created on substantially each brake application and the friction level
was erratic. From the previous test generated on the inertial dynamometer
it was assumed that the two minute blending time is insufficient to open
the fiber bundles.
Therefore, a composition designated C 0005-2 was produced by
pre-blending the friction modifiers and phenolic resin of composition D for
five minutes before adding the glass fibers and further blending this mixture
for an additional 7 minutes. Composition C 0005-2 was thereafter processad
into brake pads and installed on the test vehicle. The vehicle was driven
- 10 2,700 miles in all kinds of traffic on the streets of Detroit, Michigan.
Thereafter the disc pads on the front of the vehicle were removed for
evaluation. The disc pads during this test were worn the following amounts:
" left front disc pad wear - inner pad 0.049 inches and outer pad 0.034 inches;
and right front disc pad wear - inner pad 0.03~ inches and outer pad 0.032
inches. The rotors were substantially free from any grooves and the wear
rate measured a maximum of 0.001 inches which is acceptable. It was observed
during the road test of composition C 0005-2 that the noise level generated
during braking had decreased to a level considered acceptable. Thus, this
test substantiated the results which were obtained through the inertial
dynamcmeter testing that an optimum blending time for opening the glass
fiber in composition D is about 10 minutes.
; To further evaluate the effect of the distribution of the filaments
of glass fiber uniformly throughout a composition, milled fiber glass was
substituted into composition D in place of the fiber bundles to produce
; composition F. Composition F was blended for 15 minutes to uniformly
~ distribute the filaments throughout the mixture. Composition F was processel
~ into a friction material and tested on the Chase-type sample dynamometer.
,. .
; Composition F has a coefficient of friction illustrated by curve 10~ in
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Figure 2 and a wear illustrated by curve 111 ;n Figure 3.
3 In order to reduce the dusty conditions associated with dry mixing,
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~ latex was substituted for rubber in the dry mixture of composition D to
: produce a moist mixture identified as composition G. The latex aided in
holding the composition together until the briquettes could be formed. A
friction material sample of composition G was tested on the sample dynamometer
: and had a coefficient of friction illustrated by curve 113 in Figure 2 and
a wear rate illustrated by curve 115 in Figure 3.
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