Document LJ4bOowGGQoDMV2wvBN8edOQb
FILE NAME: Allied Signal Bendix (ASB) DATE: 1979 June DOC#: ASB207 DOCUMENT DESCRIPTION: Journal Article - A utom otive Engineering
. r 'v '-;*
m -t? $ ' : -1 T- . !}
,*'**->>H> H ?:
i ^ :-i *}i
i
C'
-, '<`lit - n: .' \-
<: i
! r r.
O
I * *1*1.J*1
0* F " 0 ,'S a I
*
-
i-'& '.S
hm l
' I - . -h*-:, M
' i ;* ><A
;' .;'' i*'[ -r*.?
|! " ; i * U l
!" !i ^y I T
JUNE 1979
l !
hSfll
*
|
r* .f '? ! ' V ' !<
' : r..
' .'K .y :jji ."':''*" ; ! ' ;j
[uture Turbochargers Aer
V i i r r ' " : i ,1
' 1: " .
'
: =' i I v rjj
mamies Airbag Gas Gnrants; j;
Designers can affect frictional coefficients of brake ana clutch linings by blending ingredients in their binders.
Friction modifiers tailor brake
New requirements for friction lining materials exist because of the elimination of asbestos in brake and clutch compositions and the use of small pads for down sized and compact cars. Semi metallic compositions generally need some friction modifiers to reduce squeal and wear and pro duce friction characteristics that are less temperature-dependent. Research on solid friction control additivies at Dow Coming has pro duced new technology by which friction and wear properties can be tailored to specific require ments.
Friction modifier*
Friction modifier additives are synergistic blends of tem pera ture-stable materials which can be incorporated into various com positions to provide specific fric tion, wear, and load-carrying pro perties. Concentrations of one to six weight percent can reduce noise levels and dependence of fric tion on speed and temperature.
Additives, such as cashew resin or graphite, have been used for many yean to control friction properties in brake and clutch compositions. Friction composites are composed of a balanced mix ture of resin plus additives and generally contain over a dozen ingredients to achieve desired
characteristics. In Europe M0S2 (molybdenum disulfide) has been u tilized 'as a friction modifier for harder brake pad compositions. Comparisons were made between M0S2 and a composition termed by Dow Coming "Friction Modi fier A" .
Phenolic retin composition*
Phenolic resins are the most common organic binders used in friction composites. Compositions of phenolics with high loading of M0S2 powder and Friction Modifier "A" were tested using an Alpha LFW-1 friction and wear testing machine.
Phenolic resin by itself does not have the best lubricating properties. Addition of MoSs or Friction Modififer "A" provided a reduction in wear and friction. Generally, the phenolic resin with Friction Modifier "A" gave lower initial coefficients of friction and wear values as compared to an equivalent weight concentration of M0S2. Coefficient of friction for the Friction Modifier "A" formu lation changed less with time than the base resin or MoSi composi tion.
Additional tests at a lower load of 13.6 kg and higher speeds re vealed that formulations with Fric tion Modifier "A" gave a more con stant coefficient of friction with
changes in speed, load, and time. At higher speeds and lower loads, no difference in wear was appar ent between M0S2 and Friction Modifier "A", but wear was sig nificantly lower than the base re sin.
Composition*
Three different brake composi tions were categorized as follows: Class A--High in asbestos and organic components Class B--Less asbestos and or ganic components plus some inor ganic components Class C--Semi-metallic non asbestos composite Class C prototype--Semi-metal lic nonasbestos Composite with 10% Friction Modifier "A" .
Table 1 lists the different char acteristics of the three classes. The brake compositions were test ed on the LFW-1 test machine.
The results of the testing are listed in Table 2. Good corre lation between the LFW-1 tests and the general characteristics provided for each of the classes was obtained. Complete correla tion existed for the wear of the brake composite and the metal mate, and very close correlation existed with noise and friction properties at low and high tem peratures.
Class C, which produced the
74
I \
I
........ . 1 j .
and
I
clutch
.i
i
i
-
/
/
!
'
characteristics
/
Characteristic ~
Pads
Wear
Friction: Cold
Hot
Noisa
Compressibility
'
Metal Mata
Duty For Usa
Table 1 -- General Properties ol Brake Linings
High Organic Class A
Poor Excellent Highest Lowest NOne Lots No scoring Standard
Medium Organic Class B
Good
Good
Lower
Higher
Little
^
Some
~~~ ' Some scoring
^ v ^Medium heavy
Low Organic No Asbestos
ClassC
Excellent Fair High + Stab. High + Stab Lots Little Lots of scoring Heavy
i
Characteristic ,
TaMe 2 1 :
1:
.
' :
LFW-1 Results at 27.3 kg Load at Variable Speeds (Step Change)
*
I
,
I
i
Class C + 10%
. Class A
Class 8
Class C
Friction Modi-
tier "A"
Wear (General Rating) LFW-1 on blocks, mg
l Friction-Cold (General Rating)
LFW-1. *T *C ) ' at2000rpm
Excellent 189
Highest 0.38 (49)
Good 381
Lower 0.22 (38)
Fair 587
High and Stable 0.48-0.39 (55)
490 1.
'1
----- 0.27-0.30 (55)
Hot (General Rating) LFW-1, M(TmQ
9 1200 rpm 91000 rpm
Lowest
0.30(107) 0.33(115)
Higher
0.28 (82) 0.38 (232)
' 0.38(143)
0.35(150)
Noise (General Rating) LFW-1
None Vary slight at one speed
Little None
Lots Some at several speeds
None
Metal Mate (General Rating) LFW-1 Test ring, mg loss
No scoring 13
Some scoring 236
Medium-heavy
scoring
634
270
I
for longer engine life quality instruments.
R604 PYROMETER
Th* rin c a ro o< the pyiometer mguitry it thit
y inttrvment which f.aturet th t readout on t 0* to t*00*F tc ti# and t 0* to '000C Seal*.
Contrattino cotort on ma dial allow aaty raadWHty and ma tetta n laro* lor accurata interpratation.
R609 TURBOCATOR
To a ttu i tha truck operator m tehtavmo grattar tuat economy and longer angina nra. tm t dual ecalt inttrumant indicete* axnautt temperature on one teala and turdocnarger booti prattura on ma ornar By monitoring Dow tealaa daily, an earty indication of angina preoiamt can Pa foraaaan
Fig. 1--LFW-1 Coefficient of friction vs. speed.
most noise, also gave the most stable frictional properties with speed and temperature as shown in Fig. 1. More consistent coef ficient of friction properties were obtained from the Class C proto type between 600 and 1200 rpm. Class C prototype produced less noise than the standard Class C brake pad. The difference be tween the maximum and mini mum coefficient of friction was less with the prototype contain ing Friction Modifier "A" than standard Class C material.
Desirable characteristics of Class B (lower wear, less noise, and a more constant coefficient of friction) may be achieved through use of the 10% Friction Modifier "A" composition. It must be noted that this percen tage should not be considered as the amount necessary for other compositions.
Commercial applications
New technology for these new friction modifiers was first de veloped in Dow Coming's Munich Research and Development Lab oratory. The first commercial eval uation and successes were in Eur opean brake pads.
Friction Modifier "A" has been used in the brake pads of a large European car for several years. The performance of the brake
pad with the new friction modi
fier was compared with another
composition containing M0S2.
Comparisons made on a dy
namometer showed the following
advantages over the M0S2 com
position:
lower noise level
less dependence of friction coef
ficient on temperature
decreased wear of the brake pad
(30% increase in lifetime)
decreased wear of the metal disc.
Since the initial usage in Eur
ope, other European brake and
clutch material manufacturers
have evaluated these new friction
modifiers. They have generally
found them equal or superior to
MoS:, but they do hot always
provide the same characteristics
since different materials are used
in each formulation!
In the U.S.A. a number of
brake and clutch friction ma
terial manufacturers have already
evaluated the friction modifiers.
Some have found that in semi
metallic brake pads without as
bestos, these new additives can
reduce noise, wear, and fade. In
some cases, no improvement was
found.
a
Based on SA papar 790717, "Controllad Friction Additive* for Brake Pad* and Clutche*." by Harry M. ScUefer and Georfe V. Kubcaak, Dow Corninf Corp.
a
A lu n . advc tech parti pow reas alun
1.1 Alur sure
4
per SiPI' gez in a ma
.2
Prc pul thir we be) OD
3.
Trutot
m1eur
an
00.
4.
Ty oa th; P/