Document DDzn4JkY2MGyQL3GaD1L8b5YQ

FILE NAME Allied Signal Bendix ASB DATE 1998 July 31 DOC ASB032 DOCUMENT DESCRIPTION Letter from Patten Agent with Attachments - Literature and Patent References on Bendix STEPHEN L. BERGER P.E. PATENT AGENT 4418 Pleasant Valley Court Oakland CA 94611 510 622-2345 Work 510 658-2256 Home July 31 1998 Walter Weathers 333 Clay Street 4440 Houston Texas 77002 BENDIX REFERENCES AND RELATED MATERIAL Dear Walter I have enclosed literature and patent references on Bendix both Aldrich and Kwolek some patents assigned to General Motors a 1950 article by a Chrysler employee and a 1979 general reference comparing different brake linings Most of the references should be explanatory after reading the enclosed three page report I wrote for NRDC in 1983. The report also details a telephone conversation I had with Aldrich in 1983. If you have any questions I will gladly discuss them with you Sincerely Stephen L. Berger P.E. Stephen L. Berger 6631 Saroni Drive Oakland CA 94611 June 22 1983 Dear Barry Here is the report on asbestos brakes for NRDC I looked through the Engineering Index from 1970 to April 1983 and the Index for SAE Transactions from 1974 to 1981 The only reference that might be of interest and which I could not locate here is a book entitled Friction Materials Recent Advances in 1978. It is by Louis based on R. Newan it might be Newman published patents and mentions commercial applications Sincerely Stephen ASBESTOS FREE BRAKES Stephen L. Berger June 22 1983 Possible replacements for asbestos brake linings pads can be divided into two groups 1 the metallic friction materials and 2 linings in which the asbestos fibers are replaced by other fibers specifically Kevlar du Pont trademark aramid fibers The linines linines following references describe the metallic brake SAE Transactions Paper No. 710591 by F. William Aldrich from the Bendix Corp. This 1971 paper describes the advantages of metallics improved wear resistance improved fade resistance improved high speed effectiveness improved frictional stability minimal noise and excellent mating surface compatibility The paper seems to imply that metallics are useful as both disc and drum brakes SAE Transactions Paper No. 750874 by John F. Kwolek at the time from the fendix Cort This 1975 paper is directed to semimetallic solid rotor disc brakes in small cars Reviewing the history of metallics the paper states that they were first developed in the 1960's and first used on foreign vehicles Police cars and taxicabs were also equipped with them In 1970 in this country metallics were used for the front disc brakes of police cars Additional costs were apparently the only reason widespread usage did not occur metallics are currently being produced for one domestic vehicle equipped with solid rotors Combinations of organic and metallic pads are being used on a domestic station wagon luxury car and several light truck applications The use of semimetallics has also been expanded to the larger disc brakes currently released for heavy trucks The above paper mentions enclosed to Rhee and Kwolek This patent is the only place a 1974 U.S. patent 3,835,118 and assigned to the Bendix Corp. I found which actually describes typical metallic brake pad formulations The patent discloses coarse sponge iron particles as a friction modifier The patent also mentions that one of the major obstacles to the acceptance of metallics as a friction material has been the poorer wear resistance of the metallics compared to organics when operating at temperatures below 325 col 3 line 66 to col 4 line ) The brake pad of the patent apparently overcomes this objection SAE Paper No. 790717 abstract only is enclosed by Harry M. Schiefer and George V. Kubczak of Dow Corning Corp. This 1979 paper describes a Dow Corning friction modifier for semimetallic brakes and clutches to reduce squeal and wear An article based on the above 790717 paper in Automotive Engineering entitled Friction Modifiers Tailor Brake and Clutch Characteristics This article gives more detail than the abstract and compares the properties of the different classes of brake linings metallic brake linings because of their hardness without friction modifiers creat much noise the squeal one hears from many European cars A telephone call to Aldrich at Bendix in Troy N.Y. 518 273-6550 revealed the following information about metallics 1 some European manufacturers have used metallics for about a decade 2 3 companies are very secretive about their proprietary brake formulations and therefore few articles giving details are published metallics work better than asbestos linings but cost more 4 more than half of GM and Chrysler disc brakes are now metallics 5 brake manufacturers will soon have to stop using asbestos because it will be too expensive for them to meet the proposed OSHA standards A telephone call to Schiefer at Dow Corning in Midland Mich 517 496-4000 did not reveal any new information but he did confirm that brake formulations are hard to find in the published literature I do not have information on changes in manufacturing equipment or processes for the metallics Erakes in which asbestos is replaced the basic formulation remaining about the same are best exemplified by SAE Transactions Paper No. 800667 by Halvar Y. Loken from du Font This 1980 paper suggests replacement of asbestos by a combination of a low cost inorganic filler with higher cost reinforcing fibers added for strength and crack resistance This approach would in principle make it possible to continue to use the production methods that have been developed for asbestos friction materials The paper presents a table which lists the advantages and potential problems of various reinforcing fibers for friction materials The problem with Kevlar Cut require special attention in mixing because the fibers are tough and do not break up but tend to clump together on prolonged mixing The paper does mention that Kevlar reinforced friction materials can outperform asbestos friction materials However Aldrich told me that Kevlar is very expensive about 6.00 per pound compared to about 0.25 per pound for asbestos and that this fact might limit the commercial applications of Kevlar On the other hand the formulations in the paper use only % Kevlar but premium quality asbestos linings use 50-50 asbestos Semi- metallics cost less than Kevlar friction materials Also enclosed is U.S. patent 4,119,591 to assigned to Bendix This discloses a friction with steel and cellulose fibers Aldrich said is worthless Aldrich and material reinforced that this patent There is also enclosed an abstract of SAE Paper No. 800979 entitled Performance Characteristics of a Asbestos Cellulose Fiber Composite Friction Material No evaluation of this paper can be made by me Lastly there are two U.S. patents 3,870,581 Manville and 4,118,528 assigned to Raybestos both disclosing glass fiber clutch facings assigned to Manhattan In conclusion asbestos free brake linings can be made using either metallic friction materials or by replacing the asbestos with a combination of Kevlar aramid fibers and filler Since metallics have already proven themselves in commercial applications in Europe and recently in the U.S. and cost less than Kevlar friction materials they will probably be the first choice of U.S. manufacturers when asbestos is eliminated f 7 cay 4,7 ~ st \ United States Patent Office Office 3,434,998 Patented Mar. 25 1969 3,434,998 MODIFIED ORGANIC BASE FRICTION MATERIAL F. William Aldrich and Theodore E. Deane Troy N.Y. assignors to The Bendix Corporation a corporation of Delaware No Drawing Flled Sept. 13 1965 Ser No. 487,052 Imt Cl 008g 51/08 51/08 0091 3:14 Fled 69.02 L'.5 Cl 260 38 5 Claims 2 smaller particle sizes There is effectively no upper limit on particle size and the entire 25 of metallic may be comprised of a single large particle or insert in the base organic However to facilitate processing a pre- < ferred particle size range is from plus 20 to minus mesh The preferred composition of the metallic frict tion modifying particle is as follows ABSTRACT OF THE DISCLOSURE An organic base friction material having dispersed therein chunks of a metallic friction modifying material to serve as the friction controlling means The metallic modifier being essentially high concentrations of metal and metal oxide powders in a base organi resin mulTIA rr In order to obtain the ultimate in friction characterise ties particularly high friction level for an organic type brake lining or friction material it is necessary to add > frit modifiers modiners are the The most common of these cured resinous particles such friction as that derived from washew nut shell liquid The use of such Cashew in particles results in increased frictionali effectiveness of the base lining or frictional material pati alarly anirient or relativelloyw temperatures How ever Such use has the disadvantage of decreased tade resistance or decreased effectiveness at elevated tempera- pum recovery und also the disadvantage of Je- creased effectiveness effectiveness over long term normal * Ta steed an inurking in required pedal pressure over lite erm he! at alter to the arse of such cured resinou pare Du use et inorganic materials of abrasive chan Mutohishus Such materials for example alumina will f increised increised effectiveness and will also offer unproved lade resistance improved recovery properties and less distdedristdrerr pestai pressure Such amnigan amnigan materials increase however with also extended use have definite disadvangats in increased noise characteristics and ex- sive wearing grooving or general destruction of the muting surface rake drum or dise Pis an object of the present invention to provide a sensumetallic triction modifier for organic base lining to praside increased friction effectiveness at both low and vusated SISTE temperatures without displaying poor fade rerecovery long term hardening excessive wear of scoting It another cheet of the present improved friction modifier for invention to provide organic base lining comprised of a semi metallic particle or chunk consisting a L metal powder or metalic oxide powder matrix DI constituent and powdered graphite all hound truether under heat and pressure by a thermosetting thermosetting phenoli revir Binder The triction modifier of the present invention is for use with an urganic base lining of the conventional type type consisting of a resin base with additive organic friction modifiers asbestos and the like The metallic friction modifier or friction con trolling means added to the basic organic lining preferably comprises Pa to 20 by volume of the total lin- ing material Below P effectiveness is not obtained above 2016uneconmical processing limitations cause the addition to become uneconomical A functional upper limit is 25 wherein the abrasive content can be expected to have deleterious effects with respect to drum or dise wear The metalli is to be added as a particle or chunk size greater than 20 mesh since the effect is masked at 2 Constituent Vol percent 10 Organic resin binder _.--..-..--- 20 and over Graphile .....-2.....2- e - ee eens ene 15-25 Ceramic Metal or powder ....--.--- wane e eee nee metal oxide powder _.._. penn eeee 10-25 30-50 15 The processing sequence is to manufacture a semimetallic friction modifying particle by combining the metal or metal oxide powder ceramic powder and powdered graphite in an organic resin binder of the thermosetting phenolic resin type which is then cured 20 under heat and pressure to form a blended tigi^ mass of metalho material This material is then broken into particles of a size greater than 20 me hand hand added to a conventional organic brake lining mix comprising preferably 12 to 20 of the volume of the finished lining material The organic lining material with semi metaliz partide added is then processed cured and snuped into a finished organic brake lining segment or block The appearance or the lining can best be described as mottled 34 compared to conventional linings when the metallic particle size is walter the prele size range of plus 20 minus < sh Neo CREATIO CREATIO constituents constituents r sillamanite multile ethusiano and zite rien oxide By results are and with ceramies of the QLTHEM silicate typ 2 Shahab Shahab and muitive though though thers Preferred metals and me qudes vie exile Mar other metals they thers rs Pe ea copper copper iron and Als Jepending 19 kicmific in extent on cost sunshi de fot met rather Sunt than wo oxide Fe il 1 JBISwill be ot noted the org the met mat Test 1. kon the 1 pr caro el binder and Cronenglis Cronenglis speaking the line of distitition distitition between charakes and metal oxides which can be substituted to the metal con- tent depends on the abrasive or haraness characterise Blake dining Manu'aglutoal a azon dar with the above teachings represe a significant advance her conventional conventional organi linings known m 196 pratt Generally spiking the advance in terms of increased increased Jaime friction effectivenes ankh various conditions conditions of operation Comparison tests reveal that increased effous tiveness is most pronounced under severe conditions of operation where conventional organic linings are the weakest For example Frake fade infused 2 his ter peralure Caused by frequent ProneProne application application air shaft shaft time interinatera''s sintera's a lessened from || or Recovery effectiveness after tade is increased axes axes of 25 High speed and burnish wear in effectiveness is im proved by a similar degree While tu some extent these ou ate predictable results of high friction characteristics of metal and ceramic particles resistant to deterioration at high temperature the main significance of the present in vention resides in the fact that this improvement is achieved without sacrificing lining wear or scoring the 65 maung brake surface such as encountered with metal base or morganic linings In fact text results have de monstrated an increase in 20 comparing an organi ticles with a full organi of lining life of pater with RP semi the same typ metallic than par We claim A mohibei arxam bo Ho MIELUI MIELUI MIELUI QURBAN~ S~ ing of an pream base for tion lining inaterial corte ing 3,434,998 3,434,998 3 from 14 to 25 by volume of a semimetallic particle of a size greater than 20 mesh said metallic particle hav- ing as constituents by volume percent graphite from 15 25 ceramic powder from 10 2a5nd metal or metal oxide from 30-50 being bound together by an organic resin binder from greater than about 20 2. A modified organic base friction material as claimed in claim 1 wherein said organic resin binder is a thermo setting phenolic resin 3. A modified organic base friction material as claimed in claim 1 wherein said ceramic powder is a cerami selected from the group consisting of sillamanite mullite magnesium oxide zirconium oxide or mixtures tuereof 4. A modified organic base friction lining material as claimed in claim f wherein said metal or metal oxide is selected from the group consisting of iron copper iron oxide or mixtures thereof 5. A modified organi b^,se friction material consisting of an organic base friction fining material containing from 15 to 20 by volume of a metall~flparticie within the size range of plus 20 minus 4 mesh said semin metallic particle having as constituents by volume percent graphite from 15-25 ceramic powder from 10-25 and metal or metal oxide from Au S925 heing bound to gether by an organic resin binder from greater than about 2077 References Cited UNITED STATES PATENTS 3.007.539 3.007.539 3.210,303 21 1961 10.1965 10.1965 Klein HIFF MORRIS LIEBMAN LIEBMAN Primars Examina R BARON Assistant Examiner 106-36 106-36 UN CL SAE TRANSACTIONS E. J. Manganiello M. J. Treasurer Joseph Secretary and General Manager PUBLISHED BY | SOCIETY OF AUTOMOTIVE ENGINEEIRNSC / TWO PENNSYLVANIA PLAZA / NEW YORK N.Y. 10001 710591 Metallics A New Type of Friction Material F. William Aldrich Automotive Control Systems Group The Bendix Corp. THE PAST TWO decades have seen rather dramatic changes in the requirements for frictional elements used in the braking systems of motor vehicles Essentially this shift in requie- ments has been in the direction of greater heat resistance greater frictional stability at a higher friction level reduced noise and extended durability In general the state development of friction materials has kept reasonable pace with these required changes through improved resin binder systems improved friction modifiers and fillers and the increased application of scientific aids for greater uniformity Although friction material development has not been re- stricted to the use of organic constituents 100, 3 substantial portion of their composition has been organic type materials and they have been thereby subject to whatever shortcomings these materials may have is unfortunate that the prime shortcoming of organic type materials namely their inherent nature to change both their form and properties with temperature is at complete odds with the requirement of frictional materials to maintain maximum uniformity and stability of effectiveness over a wide range of temperatures In the past considerable effort has gone into a potential solution to this problem of organic thermal instability in the form of development based on 100 inorganic materials namely sintered metallics However even these supposed ultimate materials had their shortcomings perhaps the greatest of which was that they also had too much sensitivity to temperature At low temperatures they were ineffective and at high temperatures they were too effective Their major advantage was low wear in the extreme temperature ranges of 1000-2000 F which made them quite successful as aircraft linings Sintered metallics did have however a potential of frictional stability superior to the organics if it could be controlled It became obvious that if the technological advantages of both the organic and sintered metallic friction types could be combined then a new generation of substantially improved friction materials could be obtained The result of this marriage is todays state semimetallic friction materials This paper will as rule not differentiate between drum brake and disc brake applications for friction materials since the basi characteristics remain essentially the same regardless of application Any difference in the requirements of friction material for these two types is ordinarily only a matter of degree with disc brakes for example generally operating at higher temperature ranges than drum brakes CLASSES OF FRICTION MATERIALS Any discussion of friction materials can be clanitied to an extent by first classifying them along general lines For pur- poses of this paper let us assume three classes for current materials Class A Class B and Class C with the latter being semimetallic As a general category Class A friction materials would be represented by production materials on American made cars over the last 5-10 year period They would be further categorized as being fundamentally organic in nature excluding of course their inorganic asbestos content common to most of them They are probably highly loaded with organic resin binders organic resin friction modifiers and ABSTRACT A new semimetallic type of friction material has been devel- oped which offers improved frictional stability and high tem- perature wear resistance Having minimal organic content these matenals avoid the thermal sensitivity to chemical and physical change characteristic of typical friction materials 2039 2040 F. WILLIAM ALDRICH natural or synthetic rubbers or elastomers They frequently also contain small amounts of graphite or other carbon type materials and possibly small amounts of inorganic wear fillers such as ground limestone As class they would be generally low in inorganic content particularly anything anything of a substantially abrasive nature Again as class they are reasonably quiet give respectable durability and under most conditions perform their frictional purpose without distinction On the demerit side sizeable increases in temperature raise havoc with their efficiency and long term use or abuse frequently lowers their effectiveness They lose friction rapidly at tem- peratures over 450-500 F and start considerable thermal decomposition above 600-650 F. Once having been in this affective temperature range they are seldom like they were before Class B materials represent a first step major compromise in attempts to improve the Class A types As class they ordi narily have higher inorganic and lower organic contents a design factor to improve their thermal stability They are most apt to have some degree of abrasive content to help stabilize their frictional properties Generally as class they have better fade resistance better recovery and overall improved frictional and thermal stability They may give good lining life at higher temperatures +450 deg but frequently at the expense of the mating surface which suffers from excessive wear grooving or scoring They are quite apt to be noisy and in terms of frictional stability may become overly effective with use or abuse thereby increasing their noise and reducing their controllability The more recent Class C or semimetallic friction material attempts to extract the desirable properties from each of the Class A and Class B types To gain maximum frictional and thermal stability it minimizes organic content but it does not ignore it since organics do add desirable properties It also maximizes inorganic content to gain thermal and frictional stability but it does not overdo these since it does not want the potential hazards they offer WEAR AND FADE RESISTANCE It has previously been noted that one of the shortcomings of organic type materials is their tendency to change form and properties at elevated temperatures It is this characteristic which contributes substantially to highly accelerated wear as the temperature goes up The property of wear is usually considered to be an economic factor only but to some extent it can also play a part in performance factors In the case of a drum braked vehicle with servo brakes moderate differ ences in side lining temperature or side lining wear rate can lead to unbalanced friction levels and severe pulls or single brake burn Whether the chicken or the egg comes first is problematical but the fundamental process is the same In disc brake the lack of servo action may prevent pulls for a longer time but moderate temperatures or wear differences at the higher operating temperature range of the disc brake can result in undesirable and substantial lining life variations side and front CLASS A CONVENTIONAL ORGANIC CLASS B HEAVY DUTY ORGANIC CLASS C SEMI METALLIC 025 INCHE 020 015 - WEAR 010+ 005t 250 300 350 400 450 500 550 600 650 LINING TEMPERATURE OF Fig 1 Wear versus temperature characteristics Class A organics do have as the temperature increases a temporary degree of protection by virtue of their fade properties By this we mean that increased temperature decreases their effectiveness and their work output thereby protecting them from further temperature increases and increased wear rate However since fade is generally less on each successive fade condition this protection is somewhat short lived Some Class A materials also have such a steep wear versus temperature curve that constant surface renewal minimizes fade and also reduces or eliminates this protec- tion Class B organics generally have improved fade resistance and more gradual wear versus temperature curves This better fade resistance tends to reduce their protection In spite of the better high temperature wear capability of the Class B types the organic materials present still cause eventual wear resistance breakdown even though it may be at a level 100-150 deg higher than a Class A type At this point however the asbestos fiber is reaching the temperature range of substantial loss of water of crystallization and is itself deteriorating actually forming new materials such as olivene Class C or semimetallic linings have a wear versus temperature curve of considerably less slope than the Class A and Class B organics The wear versus temperature curves of Class A Class B and Class C materials as taken from actual constant torque sample dynamometer tests are shown in Fig 1. It will be noticed that the Class C semimetallic is essentially insensi- tive to temperature in the 250-650 F temperature range while the Class B starts to break at +500 F and Class A starts to break at +400 F. Also note that up to 500 deg or so the Class B material wears at a rate somewhat greater than either the Class A or Class C types Because of the minimal organic content of semimetallics they also have minimal fade Based on the previous fade = protection discussion one would at first consider this a detriment In reality the semimetallic has a type of protection which organics seldom have of repetitive fade or considerably less tendency to antifade This is quite evident when one looks at what happens on typical vehicle tests involving more than one fade such as SAE J843b In Fig 2 it will be noted that for Class A and Class B organics that the second fade shows considerably less friction loss than the METALLICS 2041 i Lf LBS ! LBS lf tt] Ly FPSPS -_, FPSPS 4: 15 t4-$ 15 yy FOR i |i FOR T FORCE FORCE 7 | y7 e PEDAL fic oe PEDAL 350 PADTEMP _ Ste s = ~ KEY SEMI SEMI METALLIC woCw LASS A ORGANIL = CLASS B ORGANIC x \ L + k 50 PRO ) , , } 4 4 A AY Fo aot Re on Fig 2- Vehicle fade test characteristics 5700 lb GVW 8002468101202 8002468101202 802468101202 8002468101202 4 8 12 10 SECOND SECOND RECON RECON 10 12 2FIRST FADE elFIRST RECOVER802Y468101202 80 2468101202SECOND FADE 12 SECOND RECON ) .025 | MAX AVG AVG AVG rT ON 020 = | BASED nif .015 + MILES 10001000 .010 + PER WEAR WEAR .005 WEAR INCHES INCHES INCHES INCHES A it, | | 7) | Az A Az CLASS A ORGANIC | | AG C CLASS C SEMI MET Fig 3 Disc pad durability traffic test Class A versus Class ( first fade while in the case of semimetallic materials the second fade may show almost equal friction loss In the case of semimetallics there is reason to believe that in addition to the binding action ofthe resin system there is an inherent mechanical bonding of the metallic components Such supplementary mechanical bonding of course contributes substantially to high temperature strength and wear resistance and can take over at the point the organic binder fails There is also indication that the mechanical bonding is increased with use or duty Early semimetallic semimetallic linings showed low temperature traffic wear slightly poorer than Class A materials and more typical or the Class B types However this characteristic has now been in proved so that on normal city traffic type driving the semimetallic shows appreciably better wear Fig 3 illustrates 025- 025- _COMPLETED ONLY 4 STOPS 020 } MPH ji MPH 015 100 4 @ . STOP 010 : STOP / WEAR PG WEAR ons! | WEAR 005 | A. A. A A OA, C OG, \ , CLASS A ORGANIC CLASS C SEMI MET Fig Disc pad wear at 100 mph versus Class stop test I ull brake dynamometCe larss A actual traffic durability test results generally 350 F max on four Class A production organic disc pad linings and two Class C semimetallic materials The C2 material a more recent development shows still further gains over the CI type At the other end of the duty scale Fig 4 illustrates 100 mph wear rate results on a full brake inertia type dynamometer using these same materials Again the more recent C2 material shows improvement over the CI FRICTION Class A friction materials as rule have the highest friction when cold and the lowest friction when hot Class B materials are generally somewhat lower friction cold and higher friction hot compared to Class A types The senumetallic materials 2042 F. WILLIAM ALDRICH have substantially different friction characteristics in that they tend to increase with friction with both increased temperature and increased surface speed This characteristic has a distinct advantage for high speed effectiveness Historically high speed effectiveness of organic materials has been a problem Since increased surface speed means increased temperature the organics have usually shown poorer effective ness as the speed increased frequently requiring some exten sive power assist to maintain reasonable pedal efforts In contrast to this the semimetallic materials have tenperature speed characteristics which tend to reduce pedal effort and stopping distances from high speeds Also in contrast to previous full metallic linings sintered materials the low speed cold effectiveness is greatly improved It is acknowledged that there is still some room for additional improve- ment of this characteristic with semimetallics but to date there has been no serious deficiency in this area Actual tests have been made in the subzero temperatures of a Canadian winter Stability of friction throughout the life of the lining has also been a problem with organic types Their general characteristics of high initial friction have frequently led to initial vehicle braking instability and their characteristic of friction drop or loss after moderate abuse fade or long term light usage has frequently initiated complaints of ineffectiveness In addition their characteristic of friction peaking with severe use particularly in the case of Class B materials has led to vehicle braking stability and controllability problems By virtue of their minimum organic content semimetallic materials are much more frictionally stable over a wider range of use or abuse NOISE This nonfunctional characteristic of brake systems and friction materials has kept industry engineers hopping for years The friction materials engineer may be reluctant to agree that noises are always the linings fault but he does have to agree that there are linings more or less prone to producing noise Brake design or lining attachment not considered class organics generally tend to produce their maximum of audible response in their cold or warming condition Class B types usually duplicate the Class A in this respect and supplement this with additional noise when warm or hot The effect of this characteristic is that the driver of the vehicle has the greatest odds of obtaining noise under the conditions under which he does the majority of his driving Again semimetallic materials tend to reverse these characteristics They tend to produce minimum noise cold or warming and have their maximum noise while hot for example above 350 F On this basis then the driver is most apt to hear noise not under normal driving conditions but rather during the less frequent or abnormal conditions 007 CLASS OR A GANK ELASTOMER CONTENT | SWEL ORGANIC LHIOGWH CONTENT 7] CLASS A ELASTOMER 24 | SWELL L- O - RGA ORN GAC NC ae & INCHES oases .006 SEMI METALLIC Poe Oe pop INCHES INCHES .005 - : | i sot: 4 a Lota | th 4 A | a : DEFLECTION DEFLECTION 004 | DEFLECTION i ^' Tey ae a a, ik a i. i 4 | Io DEFLECTION 003 oa LL Ae \ te + 6.002 CCOOMMPPRERSEISON ION COMPRESION .001 COMPRES ION COMPRESSION ! Ae \ 7 # Beh RH ~ ii pe CRUSHED i CRUSHED ae 1+ _| i 1 Li! 100 200 300 400 500 600 700 800 900 INTERNAL PAD TEMPERATURE F Fig 5 . Disc pad swell and crush comparison at 5000 psi constant stress The actual compression of the pad material is a function of both the inherent compressiblity of the pad and line pressure required which is a function of the materials fade resistance This allows us to approach the compression problem from both directions reduce inherent compressibility and reduce line pressures required improve fade Class A materials because of their high organic content which tends to create inherent compressibility and also to create fade generally offer the maximum in fluid displacement Class B materials with less organic content tend to offer substantial improvement in this area Class C semimetallic materials with still less organic content and improved fade resistance have a potential of substantially greater improvement in reducing fluid displacement The accurate comparison of compressibility of various friction materials under controlled laboratory conditions is difficult due to their variable initial swell characteristics on heating One procedure which has been used involves maintaining a constant 5000 psi load on the sample and plotting swelling or compression versus temperature up to 800 F Fig 5 It will be noted that the Class A organic with high elastomer content had an initial and immediate compression prior to its showing any degree of swell All the pad materials displayed the same basic characteristics that is they showed swell under initial heating to some point in spite of the preload It will be noted that the Class A organic with high elastomer content actually crushed at a pad temperature below 400 F while a similar material with low elastomer content showed improvement but still crushed at less than 550 F. The Class B material started to compress at 550 F and failed at less than 700 F while the semimetallic material started to compress at 650 deg but would not crush at the 800 deg temperature limit of the oven used COMPRESSIBILITY OTHER CHARACTERISTICS In the disc brake the compressibility of the lining material is a significant contributor to excessive fluid displacement In the early stages of development the increased heat conductivity ofa metallic type friction material particularly METALLICS 2043 for disc pad use and its effect of fluid boil was considered a potential problem The use of a two layer organic backed semimetallic pad with the organic acting as a heat dam was indicated However many actual vehicle and dynamometer tests without such insulation failed to produce fluid boil Controlled tests did indicate fluid temperatures 60-80 deg higher with semimetallics than with organic A practical consideration however is that under extreme temperature conditions or use the wear of organic materials can be so great as to bring the actual shoe in contact with the rotor a most critical set of conditions This possibility is recognized by SAE and certain vehicle manufacturers who appraise their designs for fluid boil in the bare shoe condition Compared to organic linings semimetallic materials have relatively low coefficients of friction against the backing plate or shoe and a normal riveted attachment can result in some shift or loosening and potential cracking For this reason a roughened or grit blasted shoe surface is recommended preferably combined with a tapered rivet head Alternatives to this are a higher cost organic backed pad or integrally molded or molded assembly Although the chemical composition of semimetallics varies considerably from that of normal organic friction materials their mating surface compatibility characteristics are extremely satisfactory Compared to other materials even approaching their performance and wear level they are extremely kind to mating surfaces and generally require no special drum or rotor metallurgy or finish In the case of heavy duty drum brakes for large trucks they virtually eliminate drum spotting and heat checking typical of most materials in use SUMMARY A new type of friction material of improved frictional and thermal stability has been developed This new type of friction material when compared to current conventional types has the following characteristics 1. Improved wear resistance particularly at high tempera- ture 2. Improved fade resistance Improved high speed effectiveness Improved frictional stability 4. Minimal noise Excellent mating surface compatibility 100 100 .6.6 100 United United States Patent 19 Aldrich 54 FRICTION MATERIAL REINFORCED WITH STEEL AND CELLULOSE FIBERS 75 73 21 22 58 56 Inventor Francis William Aldrich Troy N.Y. Assignee Appl No. The Bendix Corporation Southfield Mich 812,541 Filed Jul 5 1977 . Sieerereeeerserenees US C. 74/190 188/218 R 188/251 R 188/251 A 17.4 BB 17.4 CL 260/38 42.17 260/42 18 Field of Search ....... see ee ns enenteeasensaats 17.2 38 References Cited US PATENT DOCUMENTS 3.684.062 8/1972 Johnson o 188/251 R 11 4,119,591 45 Oct. 10 1978 3,804,701 3,835,118 3,922,241 3,959,194 4/1974 111/11/9175975 5/1976 Bogner oo 17.2 Barker ceeetetsaseceescacssssreeesaeeess 260/38 Barker et we 260/172 260/172 Adelmann ...... .... 188/251 A Primary Examiner M. Woodberry Attorney Agent or Firm H. McCormick Jr. Ken C. Decker 57 ABSTRACT An asbestos free organic base friction material for use as a friction lining of a brake A combination of fiben selected from a rayon fibers thermosetting mineral and consisting of steel consisting a thermosettingthermoseting elasto- binder are combined with cashew cellulose glass meric modifiers and inorganic modifiers to produce an organic base friction material having a substantial stable coefficient of the the of friction over the normal operating range brake . 10 Claims 25 Drawing Figures .04t .04t .03 .01+ .01+ adn. 4 rN ry rt 250 300 400 500 600 700 U.S. Patent Oct. 10 1978 Sheet 1 of 5 4,119,591 .04 .03.a | .02 .01 Pat a SF see re va 500 600 250 300 400 500 600 20 700 FIG I .04 .03+ .01 250 300 400 500 600 700 FIG .04t .03- .02 3 .01 - 9 1-26 / 1-26 9 iP oneenr 400 400 500 600 700 250 300 400 500 600 700 FIG3 oat .03+ .02 -20 .01+ 250 300 400 500 -28 _- nm 600 700 FIG4 .04t .03 be .02 . 20 .01+ .01+ - 30 250 300 400 500 600 700 FIG U.S. Patent Oct. 10 1978 Sheet 2 of 5 4,119,591 L L L 20 L L L L L L 700 FIG 7 .03 .01 " 38 % 250 300 400 500 600 700 FIG 300 400 500 600 700 FIG 044 .03.02 . .01+ .01+ 250 300 400 500 600 700 FIG 11 04 x .03+ .02+ .02+ 21 .01+ 44 a oan, Se a TS SS Ein ee Cy eee 250 300 400 500 600 700 FIG 12 U.S. Patent Oct. 10 1978 Sheet 3 of 5 4,119,591 4,119,591 .04 .03 .02 ] .01 21 a -46 -46 250 300 400 500 600 700 FIG 13 .034 .02 -21 250 300 400 500 600 700 FIG 14 .04 .03 .01 = -50 -50 -50 300 400 500 600 700 FIG 15 .04 .03 .02.01 + -52 == oe -52 t- 250 300 400 500 600 700 FIG 16 .04 .03+ .02+ 21 .01+ 54 a prereet arent fp emreendirenien 300 400 500 600 700 FIG 17 .04 .03+ .02+ 21 10 we -56 250 300 400 500 600 700 FIG 18 U.S. Patent Oct. 10 1978 Sheet 4 of 5 4,119,591 4,119,591 .04+ .03 . .01 a L- 58 , 7 250 300 400 500 600 700 FIG .03+.03+ .02+ .02+ .02+ .02+ 21 .01 -60 -60 devel apomnt ab > 250 300 400 500 600 700 FIG 20 04+ + .03 .02 + .01 21 67-62 250 300 400 500 600 700 FIG .04 .03. .02 + .01 21 4-64 / 21 : re cee te | 250 300 400 500 600 700 FIG .04 .03+ .02 21 .01 < 7 ~66 4 +. rN he + + 250 300 400 500 600 700 FIG 23 .04 .03+ .02+ .01 at, _-~~68 250 300 400 500 600 700 FIG 24 4,119,591 1 2 FRICTION MATERIAL REINFORCED WITH STEEL AND CELLULOSE FIBERS dispursed throughout a friction lining provide sufficient strtoealn low g a ft ricth ion lining made of the composi- tion to withstand dynamic loadings without deteriorat- BACKGROUND OF THE INVENTION Organic friction material compositions currently used in clutch and brake linings of vehicles must be capable of withstanding severe operating temperatures and dy It is therefore the object of this invention to provide structural asbestos free organic friction lining with sufficient structural strength to repeatedly withstand dynamic loads without deteriorating when used in a brake lining namic pressures experienced during repeated applica- It is another object of this invention to provide an tions To prevent a deterioration in performance and 10 organic friction material with a foundation material physical degradation during an application the linings are reinfoced by asbestos fibers randomly dispursed throughout a resin matrix However recent medical evidence indicates that asbestos fibers can cause health hazards of the lungs in persons exposed to asbestos fibers of the type used in the manufacture of clutch and brake lining The health hazard is caused by the polution of the surrounding environment with small parti- cles of asbestos during the mixing ofthe friction compo- sition in a manufacturing facility In an effort to reduce the environment contamination by the asbestos fiber and thereby continue manufacturing asbestos based organic friction linings a water slurry process is disclosed in U.S. patent application made up of a combinaoftait loeanst 3 percent steel fiber and 5 percent cellulose fiber The steel and cellulose fibers being dispursed throughout the friction material to uniformly distfr orci esb exu ertt ed e on a brake lining and thereby prevent degradation thereof during re- peated dynamic brake engagements It is another object of this invention for providing an organic friction material with a base material of steel fiber and cellulose fiber to establish a substantially uni- form wear characteristic over the operating range of friction lining These and other objects should be apparent from reading this specification and viewing the drawing Ser No. 754,477 has been evaluated The water slurry 25 BRIEF DESCRIPTION OF THE DRAWING can be transmitted throughout a manufacturing facility without contaminating the surrounding environment with asbestos fibers However before the friction mate- rial 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 FIGS 1-24 ofthe drawing are graphs comparing the wear characteristics of the asbestos organic friction material composition made according to this invention with a typical asbestos organic friction lining and FIG 25 is a table illustrating asbestos friction material composition made according to this invention In another attempt to reduce the occupational health DETAILED DESCRIPTION OF THE hazards in the manufacture of linings it has been sug- INVENTION gested that the asbestos fiber be replaced with glass 35 fibers In order to evaluate the asbestos friction material U.S. Pat No. 3,967,037 discloses several lining com- compositions disclosed by this invention typical asbes- positions utilizing fiber glass From experimentauon it tos base friction material compositions were used as a has been determined that such lining compositions are standard to determine the wear rate and coefficient of acceptable however in admixing the ingredients the 40 friction characteristics of the asbestos base friction fiber glass tends to ball and thereby reduce the continu- material when used in a brake ity of the friction material In addition when fiber glass FIG 25 illustrates the relationships of the vanous base friction materials are mated with a steel brake rotor combinations of the fibers substituted for asbestos as or drum an unacceptable wear condition occurs disclosed by this invention U.S. Pat No. 3,896,075 discloses another friction 45 The ingredients in the asbestos and asbestos fric- composition wherein the asbestos in an organic lining is replaced with basalt fibers Because of the process required to reduce the mineral basalt into a fiber state the use of such friction composition to date has not received tion material formulations were processed into brake friction lining in the following manner as described in detail for the base line asbestos material composition A. The asbestos fiber dry phenolic resin equal parts of open acceptance as a substitute for asbestos based or- cashew nut powder and synthetic rubber scrap and ganic friction materials barytes were mixed together until a homogeneouS MALK- Later as disclosed in U.S. Pat No. 4,019,912 the reinforcing of the structure of a resulting friction lining was ture was achieved Thereafter the mixture was placed in a mold and compacted into a briquette The briquette through achieved the use of carbon fibers However was then transferred to a preas and compressed by a the pyrolysis step required to reduce the rayon or cellu- 55 force of about 5,000 pounds per square inch while the lose fiber to a carbon fiber would destroy the elastomers temperature of the briquette was raised to about 250 F. and inorganic fillers found in organic friction composi- tions temperature The 250 F. causes the phenolic resin to flow throughout the mixture and establish a matrix for SUMMARY OF THE INVENTION holding the other ingredients in a fixed position The briquweastttheen transferred to a caring oven having I have developed an organic friction material compo- a temp of e abour t 5a 00 Ft . tou furr there set the resin sition consisting of an asbestos free foundation material The briquette was then ground to a specific size corre- organic and inorganic friction modifiers retained in a sponding to a brake pad This brake pad was then matrix of a thermosetting resin The asbestos free foun- placed on a dynamometer and from the tests performed dation material includes as a minimum of 3 percent steel 65 thereon it was established that the composition Formula fiber and 5 percent cellulose fiber and other fibers such A had an average coefficient of friction of 0.36 at 450 as carbon mineral and fiber glass The steel and cellu- lose fibers when randomly orientated and uniformly F. and a wear rate as illustrated by base line 20 shown in FIGS 1-9 20 and 21 4,119,591 3 4 In order to establish a broader base for evaluating the ^ nan attempt to smooth out the wear rate of composi- asbestos friction material compositions a second tion No. 5 as illustrated by line 30 ^finFIG 5 a filler of asbestos friction material identified as Formula B was % by volume of carbon was added to composition No compounded In Formula B the large amount of asbes- to produce composition No. 6 in Table 1 The compo- tos in Formula A is replaced by additional cashew fric sition No. 6 was made into a brake friction lining and tion powder and a filler of graphite particles to produce a brake lining The average coefficient of friction of when evaluated in the dynamometer test an average coefficient of friction of 0.28 at 450 F. was obtained Formula B a brake pad made from using the same dyna- and a wear rate illustrated by line 32 in FIG 6 was mometer test as used to evaluate Formula A was found produced to be 0.35 and the wear rate is illustrated by line 21 in 10 In a further attempt to broaden the base for the inor- FIGS 10 1a9nd 22 24 ganic filler modifiers a composition No. 7 as shown in Upon initial evaluation of the asbestos friction FIG 25 was produced in composition No. 7 a mini- materials it became evident that the removal of asbestos mum of % by volume of rotten stone was added to the from the mixture left the remaining ingredients in a dry basic steel and cellulose fiber composition When the crumbly state during the briquette forming stage brake lining of composition No. 7 was tested on the Therefore it was necessary to add part of the phenolic dynamometer and an average coefficient of friction of resin as a liquid to all the asbestos composition in 0.32 at 450 F. was obtained and a wear rate as illus- order to produce a composition capable of being han- trated by line 34 in Flg 7 was achieved died as a preformed briquette In order to improve the wear rate of the asbestos The asbestos friction material composition No 1 friction material whiting was selected as the inorganic shown in FIG 25 wherein a combination of steel fiber modifier and composition No. 8 shown in FIG 25 was and cellulose fiber were substituted for the asbestos produced When the dynamometer test was run for the fiber was formulated in the same manner as Formula A brake lining made from composition No. 8 an average and formed into a brake lining When the dynamometer coefficient of friction of 0.30 at 450 F was obuined tests were performed composition No. 1 had an aver and a wear rate illustrated by line 36 FIG 8 was age coefficient of friction 0 34 at 450 F and a wear rate produced illustrated by line 22 FIG 1 As can be seen the wear in an attempt to improve the coefficient of friction of rate approaches that of the asbestos material of Formula composition No. 8 the friction producing material kryo- a which is currently accepted by the vehicle industry lite was added thereto to produce composition No 9 In order to establish a group of morganic fillers ac- 30 shown in FIG 25 When the brake lining of composi cepable for use in a asbestos friction matenal talo tion No. 9 was evaluated in the dynamometer test an was substituted for the whiting of composition No 1 average coefficient of friction of 37 at 450 F was and composition No 2 shown in FIG 25 was estab obtained and a wear rate illustrated by line 38 in FIG 9 lished The dynamometer test for the brake lining made was produced from composition No 2 indicated than an average coef 35 Composition No 10 shown in FIG 25 includes the ficient of friction of 0 30 at 450 F and a wear rate as same type ingredients as Formula B with the exception illustrated by line 24 FIG 2 could be expected from of the asbestos friction material To establish broad base this composition for the friction material and improve the coefficient of Because ofthe availability of barytes and its low cost a series of compositions including barytes were devel fnction of the asbestos material the cellulose fiber was replaced with glass fiber When the brake lining oped composition No. 10 was evaluated by the dynamometer As shown in FIG 25. composition No. 3 was formu- test an average coefficient of friction of 0 35 a1 450 F lated When the brake lining made from composition was obtained and a wear rate illustrated by line 40 in No. 3 was evaluated by the dynamometer test a coeffici- FIG 10 was achieved From this test it was determined ent of friction of 0.31 at 450 F was obtained and a wear 45 that while glass fiber when added to asbestos fnc- rate illustrated by line 26 FIG 3 was produced tion material compositions does increase the coefficient Even though the wear rate of composition No 3 of friction however the wear rate is also increased could be expected to be better than that of Formula A Thereafter composition No II shown in FIG 25 it was felt that the coefficient of friction could be im- was developed with wood flour added in place of the proved through the addition of either a different filler 50 glass fiber of composition No. 10. When the brake lining or fiber material Through experimentation it was deter- of composition No. 11 was evaluated through the dyna- mined that glass fiber has a higher coefficient of friction than cellulose fiber Therefore glass fiber was substi- mometer test a coefficient of friction 0 37 at 450 F was obtained and a wear rate as illustrated by lin^'42 in FIG tuted for the cellulose fiber and composition No 4 11 was produced From this test it was determined that shown in FIG 25 was produced When the brake lining $$ cellulose type fibers when combined with steel fibers of composition No. 4 was tested through the dynamom- produced a more satisfactory asbestos friction ma- eter test a coefficient of friction 0.35 at 450 F was terial composition than when a single fiber material is produced and a wear rate illustrated by line 28 in FIG used 4 was achieved Unfortunately with this amount of Thereafter an attempt was made to establish the glass fiber in composition No. 4 surface polish or wear 60 optimum limits for steel cellulose and other fibers of a rotor or drum brake could be expected when used as the foundation material .or a asbestos Therefore the amount of glass firber was reduced friction material Thus composition No. 12 shown in and cellulose fiber added to produce composition No. 5 FIG 25 was produced In composition No 12 the shown in FIG 25. When the resulting brake lining made volume of cellulose fiber was double that of the steel by composition No. 5 was evaluated in the dynamome 65 fiber When the brake lining made from composition ter test a coefficient of 0.32 at 450 F. was obtained and No. 12 was evaluated through the dynamometer test a a wear rate illustrated by line 30 FIG 5 was coefficient of friction of 0.35 at 450 F. was obtained achieved and a wear rate as illustrated by line 44 FIG 12 was ORGANIC FRICTION MATERIAL COMPOSITION TYPICAL ASBESTOS FRICTION MATERIAL ASBESTOS FRICTION MATERIAL FORMULAS U.S. FORMULAS INGREDIENTS A ASBESTOS FIBER 52 STEEL FIBER CELLULOSE FIBER B 123456789 123456789 123456789 10 11 | 12 14 15 | 16 | 18 19 20 24 43 ... ... 710 7 10 10 Paten 25 GLASS FIBER 53 10 3 WOOD FLOUR PHENOLIC DRY 25 RESIN LIQUID a ORGANIC 22 MODIFIERS b INORGANIC ' MODIFIERS 10 Oct. 16 15 15 17 20 20 18 20 20 2017 20 10 ... || ... || ...... || | ... ... 34 40 45 45 40 25 1978 1 2 4 5 6 7 0 9 0 1 12 5 147 15 15 17 ond] 9 20 23 24 ] ) | ] | f 22 7 | 21 23 12 15 12 20 14 22 24 CASHEW NUT POWDER NATURAL RUBBER SYNTHETIC RUBBER SCRAP LATEX CRUDE MOLASSES ASPHALTIC BASE MATERIAL ETC. BARYTES WHITING TALC ROTTEN STONE STONE CARBON PARTICLES COPPER POWDER WOLLASTONITE KRY^ LITE ALL PERCENTAGES GIVEN IN VOLUME OF TOTAL GRAPHYTE PARTICLES CRYOLITE IRON OXIDE COMPOSITION She t ^ AT LEAST 25 OF WHICH IS CASHEW NUT POWDERS 5 ) AT LEAST 16 OF WHICH IS WHITING AT LEAST 12 OF WHICH IS BARYTES 13 AT LEAST 16 OF WHICH IS TALC 14 AT LEAST 3 OF WHICH IS CRYOLITE of AT 5 3 AT LEAST 10 OF WHICH IS BARYTES 15 AT LEAST % OF WHICH IS ROTTEN STONE 4 AT LEAST 15 OF WHICH IS BARYTES 5 AT LEAST 12 OF WHICH IS BARYTES 16 AT LEAST 17 AT LEAST % OF WHICH IS IRON OXIDE % OF WHICH IS COPPER POWDER AT LEAST % OF WHICH IS CARBON LEAST % OF WHICH IS BARYTES AT LEAST % OF WHICH IS AT LEAST 11 OF WHICH IS AT LEAST % OF WHICH IS ROTTEN STONE WHITING KRYOLITE LEAST % OF WHICH IS WOLLASTONE LEAST % OF WHICH IS CARBON 4,19,591 LEAST 12 OF WHICH IS BARYTES IS BARYTES LEAST 11 OF WHICH IS BARYTES AT LEAST % OF WHICH IS BARYTES 22 LEAST 10 OF WHICH IS SILANIZED MINERAL FIBER 23 24 LEAST LEAST 25 OF 10 OF WHICH IS WHICH IS BARYTES CARBON 4,19,51 FIG 25 4,119,591 5 6 produced Unfortunately composition No. 12 was spongy and therefore it was determined that the cellu- lose fiber should be reduced structural strength in the friction lining the carbon particles can be replaced with carbon fibers In a further attempt to establish a base for the inor- Thereafter the cellulose fiber of composition No 12 was reduced to produce composition No. 13 shown in FIG 25. A brake lining made from composition No. 13 was evaluated in the dynamometer test had an average ganic friction modifiers the volumetric percentage of the steel fiber was increased and a minimum volumetric percentage of barytes was established at 12 to produce composition No. 21 shown in FIG 25. When 5 coefficient of friction of 0.32 at 450 F. and wear rate brake lining made from composition No. 21 was evalu- as illustrated by line 46 in FIG 13. This composition was not spongy however it should be noted that the ated through the dynamometer test a coefficient of 10 friction of 0.32 at 450 F. was obtained and a wear rate coefficient of friction was reduced illustrated by line 62 in Fig 21 was produced Therefore in order to increase the coefficient of fric- Thereafter the steel fiber was maintained at % by tion cryolite was added to the composition No. 13 and volume and silanized mineral fiber was added to pro- composition No. 14 shown in FIG 25 was produced A brake lining made from composition No. 14 was evalu duce composition No. 22 shown in FIG 25. A brake lining made from composition No 22 was produced ated through the dynamometer test had an average and when evaluated in the dynamometer test a coefficie coefficient of friction of 0.37 at 450 F. and a wear rate ent of friction of 0.28 at 450 F. and a wear rate as illustrated by line 48 in FIG 34 illustrated by line 64 in FIG 22 was produced Since the wear rate and coefficient of friction of com From the foregoing test it should be evident that the position No 14 was much improved over Formula B. 20 range of steel fiber should be maintained between 3 to the organic modifier base was expanded through the 15 volume percent of the total mixture However unce substitution of rotten stone for the cryolite to produce the optimum range of cellulose and other fibers had not composition No. 15 shown in FIG 25 When a brake lining made of composition No 15 was evaluated through th dynamometer test an average coefficient of 25 friction of 33 at 450 F. was obtained and a wear rate illustrated by line 50 FIG 15 was produced Composition No 14 was further expanded through the substitution of iron oxide for the cryolite to produce composition No. 16 shown in FIG 25 When a brake lining made of composition No 16 was evaluated through the dynamometer test a coefficient of friction of 0 34 at 450 F. was obtained and a wear rate as illus- trated by line 52 FIG 16 was produced been established therefore composition No. 23 shown in FIG 25 was devised In composition No. 23 the cellulose fiber was increased to a maximum of 25 percent of the total volumetric percentage of the composition while at the same time the cashew nut powder was reduced to 15 When a brake lining made from composition No. 23 was evaluated through the dynamome- ter test a coefficient of friction of 0.45 at 450 F was obtained and a wear rate as illustrated by line 66 in FIG 23 was produced As seen composition No 3 almost matches the wear rate for currently acceptable asbestos lining and could be accepted by most vehicle manufac- Composition No 14 was still further expanded 35 turers without extended qualification testing Thus the through the substitution of copper powder for the cryoIne and glass fiber to produce composition No 17 shown in FIG 25 A brake lining made from composi- industry would be able to meet the Federal Clean Air and Health Standards of 1975 within the prescribed time set for compliance ton No 17 when evaluated through the dynamometer test had a coefficient of friction of 0.34 at 450 F. and a To substantiate the results of composition No 23 another composition No. 24 shown in FIG 25 was wear rate as illustrated by line 54 FIG 17 prepared by reducing the percentage of cellulose fiber Composition No 14 was sull further expanded while increasing the resin content and substituting car- through the addition of fiber glass to the base matenal in produce composition No 18 shown in FIG 25 A bon in powder form for a portion of the barytes There after when a friction lining made from composition No brake lining made from composition No. 18 when eval- 45 24 was evaluated through the dynamometer test a coef- uated through the dynamometer test had a coefficient of ficient of friction of 0.28 at 450 F was obtained and a friction of 0.37 al 450 F. and a wear rate as illustrated wear rate as illustrated by line 68 in FIG 24 was pro- by line 56 in FIG 18 duced In order to establish relationship between steel fiber From the foregoing compositions it was determined and cellulose fiber in the asbestos friction material 50 that while steel and cellulose fiber produce an accept- the cellulose fiber was eliminated from the basic compo able asbestos friction material when combined sition and composition No. 19 shown in FIG 25 was together with inorganic modifiers which can include produced in an attempt to provide composition No. 19 glass mineral and carbon fibers produce a friction mate- with an adequate coefficient of friction at least % by rial with a substantially uniform wear rate throughout volume of Wallastonite was added to the composition 55 the operating range of most brake linings A brake lining made from composition No 19 when 1 claim evaluated through the dynamometer test had a coeffici- ent of friction of 0.32 at 450 F. and a wear rate illus- 1. An organic friction material for use as a friction lining consisting of a mixture of trated by line $ in FIG 19 8-50 by volume of a combination of asbestos As seen in FIG 19 the wear rate for composition No. 60 fibers selected from a group consisting of fiber glass 19 was not as good as asbestos Formula B. Thus the mineral fiber at least % by volume of steel fil .rz steel fiber in composition No. 19 was reduced and car- and at least % by volume of cellulose fibers bon particles were added to produce composition No. 12-35 by volume of thermosetting phenolic resin 20 as shown in FIG 25. When a brake lining made of 5-35 by volume of cashew nut particles composition No. 20 was evaluated through the dyna- 3-20 by volume of elastomeric modifiers and mometer test a coefficient of fricuon of 0.37 at 450 F. 10-55 by volume of inorganic modifiers said thermo- was obtained and a wear rate illustrated by line 60 was setting phenolic resin being responsive to heat to produced In some applications in order to achieve form a matrix for holding said asbestos fibers 4,119,591 7 cashew nut particles elastomeric modifiers and inor- 5. The organic base friction material as recited in ganic modifiers in a fixed relationship said asbe- claim 4 wherein said inorganic modifiers are selected stos fibers and phenolic resin matrix providing struc- from a group consisting of barytes whiting talc rotten- tural strength for allowing the friction lining to with- stone wollastonite pumice iron oxide powder copper $ oxide powder carbon and silanized mineral particles stand dynamic repeated engagements with a rotating 6. The organic base friction material as recited in member and providing a substantially uniform wear claim 1 wherein said asbestos fibers include up to rate up to 600 F. during a dynamic engagement 10 fiber glass fibers 2. The organic base friction material as recited in 7. The organic base friction material as recited in claim 1 wherein said phenolic resin includes at least claim 1 wherein said asbestos fibers include up to 12 dry phenolic resin powder 3. The organic base friction material as recited in claim 2 wherein said phenolic resin includes up to 18 liquid phenolic resin to attenuate segregation of said elastomeric and inorganic modifiers prior to the appli- cation of heat to the mixture 4. The organic base friction material as recited in claim 3 wherein said elastomeric modifiers is selected from a group consisting of natural and synthetic rubber scrap natural latex crude molasses and asphalt 10 wood flour fibers 8. The orgba asenfri ictc ion mateasrrei cita edl in claim 1 wherein said asbestos fibers include up to 10 silanized mineral fibers The organic base friction material as recited in claim 1 wherein said asbestos fibers include up to 10 carbon fibers 10. The organic base friction material as recited in claim 1 wherein said phenolic resin includes at least % liquid resin 40 4s 50 ... 65 SAE TRANSACTIONS Rodger F. President M. J. Treasurer Joseph Secretary & General Manager PUBLISHED BY SOCIETY OF AUTOMOTIVE ENGINEERS INC./400 Commonwealth Warrendale Pa 15096 _ e a i 6 750874 Friction Materials for Small Car Solid Rotor Applications John P. Kwolek Automotive Control Systems Group Bendix Corp. WITH CONSUMER INTEREST in lower priced venicles and improved fuel economy on the increase domestic vehicle manufacturers are giving more serious thought towards producing compacts vehicles having curb weights less than 2600 lbs Foreign vehicle manufacturers have pro- duced vehicles equipped with solid rotor disc brakes in this weight category for over a decade but most American manufacturers have beer hesitant to use the solid rotor disc brake systems found on a majority of these lighter weight cars due to several factors From the brake engineer's point of view while solid rotors offer lower cost the ventilated rotor offers substantial improvement in brake cooling over solid rotors thereby lowering the brake lining temperatures encountered during usage The front brake temperature profile for a durability test of a 1973 Domestic Drum Station Wagon is illustrated in Figure 1. This vehicle had standard ventilated rotors which weigh 27 lbs each the brake test weight was 5860 lbs operating tem- peratures generally ranged between 150 and 340 The same durability test was also conducted on a 1973 European made vehicle equipped with wheel disc brakes Brake test weight of this vehicle was 2800 lbs with the solid rotors weighing only 6 lbs each A comparison of the front brake temperature profile for this vehicle see Figure 2 with that of the 5860 | lbs Station Wagon test indicates the average brake lining temperatures increased 75 with peak temperatures 150 hotter than those experi- enced on the heavier station wagon Several differences can explain these re- 500 + | + F 400 { rs - + > - + + + + + 4 a + + oe] + + + 4 300+ TEMPRAUE 200 1007 0 5 10 15 20 25 30 CHECK POINTS Fig Average front brake temperature profile 1973 station wagon @ 5860 lb G.V.W. ventilated rotors 11 cycles sults with the most influential factor being rotor weight and design The purpose of dis- cussing these temperature profiles is to emphasize the fact that the lighter weight vehicles equipped with solid rotors require linings which can successfully operate at higher temperatures than those experienced on the heavier domestic vehicles presently produced with ventilated rotors ABSTRACT metallic friction materials recent- ly developed offer significant improvements in lining life rotor compatability and noise over organic friction materials on small cars equipped with solid rotors Improvements originally predicted from full brake inertia dynamometer tests have been verified on vehicle durability and fleet tests 2369 2370 500 + + * : 400 F 500 TEMPRAU nr) 10 15 20 25 30 CHECK POINTS Fig Average front brake file 1973 sedan @ 2800 lb rotors 11 cycles temperature proG.V.W. solid TYPES OF FRICTION MATERIALS Friction materials are designed for specific applications with the composition and method of manufacture determining the particular properties of any specific material The primary function of the friction material is to produce a relatively high constant coeffi- cient of friction under the conditions antici- pated in exhibit use The excellent friction material must also resistance to Wear and opposing surface compatability under these same conditions A previous classification of friction materials 1 gives some insight into the fundamental compositional differences and how these differences affect friction and wear in brake lining presently used by vehicle manufacturers The organic friction materials presently used on domestic passenger cars equipped with ventilated rotors which are referred to as Class A materials are fundamentally organic in nature excluding their inorganic asbestos content As a class these materials are reasonably quiet give respectable durability and under most conditions perform their frictional purposes ... namely maintain ac- ceptable friction and fade resistance Class A type friction materials are not generally found on because 1. Lining wear solid rates rotor applications , increase exponential- ly at the higher operating temperatures Fig- ure 3 Numbers in parentheses at end of paper designate References J. P.KWOLEK CLASS A CONVENTIONAL ORGANIC CLASS B HEAVY DUTY ORGANIC - CLASS .030 INCHES .025 INCHES SEMI METALLIC . + 9 -+----+--- , INCHES .020 + .015 WEAR .010 Po .005 {Fs 250 350 450 650 LINING TEMPERATU-RFE Fig Average wear versus temperature characteristics inertia dynamometer 1740 lb wheel load ventilated rotor 2 They exhibit more fade and over recovery when compared to Class B organics or met- allics Figure 4 Organic friction materials designed for heavy duty Class B generally have higher in- organic contents to improve their high tempera- ture wear resistance and fade resistance Ab- rasives are generally added to achieve higher friction Historically these types of materials have been used on solid rotor applications because they are more suited to higher operating temperatures than Class A type or- ganics Figure 3 and the fade performance Figure 4 demanded by this class of vehicles 1600 PSI PSI 1200 PRESURE PRESURE PRESSURE PRESSURE PRES URE PRESSURE 8007 PRESSURE PRESSURE LINE LINE LINE 400 FADE + : RECOVERY oy SEMI MET CLASS B CLASS A + + 1 + + ia bo * - ee 5 10 15 5 10 STOP NO Fig Green fade and recovery 1973 sedan @ 2800 lb G.V.W. 4 solid rotors fade 60 mph 15 fpsps 35 second interval recovery 30 mph 10 fpsps 1 mile interval FRICTION MATERIALS But as so commonly found in friction material development improvements in one area usually results in losses in other areas Class B materials generally exhibit higher low temperature wear rates and frequently either groove score or wear the mating rotor surfaces They are also quite prone to generate objectional noise The success of sintered metallic friction materials for specialized applications such as Jet Aircraft Brakes Heavy Duty Clutch Facings and Police and Racing Car Brakes suggested metallic composites would some day find usage in Automotive Braking Markets if refinement could be made metallics the third class of materials rely heavily on iron steel and graphite substitutions for the organic and asbestos materials usually found in the Class materials But unlike the sintered metallics metallics can use organic components to add desirable properties As in all friction materials the use of abrasives must be minimized in order to maintain acceptable mating surface compatability HISTORY OF METALLICS The metallic formulations developed in the 60's for heavy duty ventilated rotor applications were first released on foreign vehicles equipped with solid rotors These vehicle manufacturers released metallic formulations for police cars and quickly expanded their usage to taxi cabs and a few vehicles sold to the general public In 1970 domestic manufacturers released metallic formulations for the front ventilated rotors disc brakes of police cars based on the success of these materials in meeting Los Angeles Police Dept. Braking Stan- dards By this time the advantages of semi- metallics over conventional organics were clearly understood 1. Improved friction stability 2 Improved fade resistance 3. Excellent high temperature wear resis- tance 4 Minimal speed spread 5 Excellent compatability with rotors 6 High performance with minimal noise Even these with advantages widespread usage could not be anticipated on domestic vehicles sold to the general public because of the additional costs Raw material mix cost represents the major factor in the premium prices of metallics These compounds generally weigh approximately twice as much as Class A organics and use materials which cost more per pound than those found in conventional Class A organics The smaller sized pads used in small car solid rotor applications drastically reduce the affects of raw material mix cost and metallics can be competitive with many of the higher priced heavy duty 2371 Class B organics on small cars With the advent of FMVSS 105-75 testing it became apparent that while metallics showed excellent friction stability from 2nd through 4th effectiveness the burnished friction had to be improved Still another area of concern was initial wear referred to by some as low temperature wear One particular type of dynamomette esrt procedure a wear versus temperature schedule indicated higher wear rates than those experienced with conventional organics at low tem- peratures Subsequent dynamometer tests and microscopic examination of the materials proved this to be an initial wear problem and that conditioning of the lining at higher tem- perature and by extended usage dramatically improves lining life at low temperatures see Figure 5 The analysis of numerous vehicle tests conducted confirmed that the wear rate of metallic formulations improves with usage see Figure 6 PREVIOUSLY CONDITIONED TO 250 PREVIOUSLY CONDITIONED TO 400 PREVIOUSLY CONDITIONED TO 550 -----<== .020 WEAR 2010 MAX .000 + * + : . INITIAL RANGE FOR 250 WEAR 7 ee r e + + + tw oer He en 1500 ab eeeePPT ene eles Peet ta eho a one, ons 300 600 900 1200 1500 TOTAL STOPS AFTER PRECONDITIONING Fig Effects of preconditioning metallic on subsequent low temperature incremental wear inertia dynamometer 1740 lb wheel load ventilated rotor all stops from 50 mph 12 fpsps deceleration 6,30,0 9.300 FIRST 1,070A 0 LAST 4,000MI 31,400 54,900 MIN MAX Fig Incremental mileage projections for Detroit Durability of Metallic 1973 domestic sedan 5560 lb G.V.W. Even with this knowledge the development program for metallics concentrated on improving burnished friction and initial wear characteristics The program led to significant improvements and resulted in the issuance of a patent 3 for this new type of material burnished front torque was in- creased 20 and initial low temperature wear rates were decreased to levels comparable to those obtained with conventional Class A or-