Document N21KwB3x5dpRKpjv3YMjqv65w

FILE NAME: AMMCO (AMC) DATE: 1949 June DOC#: AMC024 DOCUMENT DESCRIPTION: Trade Journal Article - Phenolics Brake Linings ''L *- h' /X t . ' -i!r: ' i*V fi - -*% - i i t JUNE 1949 rt &** t Research on broke lining materials and fastening methods requires extensive testing and checking on wear of lining C D J S T Sf PUSSFLl VFG CO. y In the Permafuse bonding method, brake lining and im pregnated tape are clamped to the shoe and placed in oven in M u Linings Resin binders give improved frictional characteristics, longer life, and greater stability under operating conditions; hnnd iininas to shoes, eliminatinq all riyets TEN MILLION to twelve million pounds of pheno lic resins were used in 1948 in the manufacture of brake linings for automobiles. In addition, the comparatively new development of bonding linings to brake shoes with phenolic adhesives, instead of using rivets, opens up large new resin markets. Of all the brake linings manufactured today, it is esti mated that over 90% contain 2 to 25% by weight of phBeninodliecrsrewsinhsic. h are commonly used to give the re quired frictional characteristics to brake linings were formerly rubber or asphalt. Today, synthetic resin binders, particularly phenolics, give longer life to the linings, improve frictional qualities, and provide better resistance to oil, grease, ana water. Besides all this, certain phenolic resins can be used to pro duce linings that tend to be stable in operation re gardless of tem perature or humidity. The resins may be used alone or in combination with asphalts, tars, drying oils, sulfonated oils, casein, rubber, and gums. After years of experience, the automotive manu facturers have settled upon the following 10 essen tial qualities tor tne ideal brake lining: 1) proper coefficient of friction, which governs the rate of stopping, 2) resistance to wear, 3) stability of fAc tion, hot and cold, 4) stability of friction, wet and dry, 5)-silent action, 6) non-abrasive action, so that metal drums will not become scored, 7) good pedal feel, 8) lack of odor, 9) minimum loss of reserve under usage, and 10) good mechanical strength. Most engineers are agreed that the first two quali ties are paramount. From there on, however, there is little accord on the order of importance. Each year there are differences in automobile brake design which call for differences in brake linings. As a con sequence, linings must be tailor-made for specific jobs. One large manufacturer of phenolic resins puts it this way: "By varying the ingredients that go into brake linings, so may the 10 properties be varied. Therein lies the art of making friction materials." Three types available Brake linings in use today may be divided into woven, molded fabric, and molded or bonded fiber types. The woven lining consists of an asbestoscotton-wire fabric, impregnated with a resin or other binder and calendered to size. The ingredients areused in the following range of proportions: asbestos, 41 to 65%; cotton, 7 to 18%; wire, 20 to 34%; and binder, 4 to 16% by weight. Molded fabric linings Molded fabric lining consists of a waterproof base on which a friction coating is built up to pre-mokled size and is then cured to exact dimensions with heat and pressure. 73 MODERN PLASTICS Asbestos-cotton-wire woven fabric is usually used as the base of molded fabric linings. The fabric is impregnated with the binder as in the case of woven linings, but the binder is used to the extent of only 2 to 5 percent. Some phenolic is used for this type oafrelisntiinllgi,nbguetnderryailnugseo.ils and bituminous materials Bonded fiber linings The third type of brake lining, probably the more popular today, is the molded or bonded fiber lining. This type of lining is made from loose fibers which are impregnated with binder materials by either dry mixing and molding' or wet mixing and forming with subsequent drying. These molded fiber linings duosutahlelywcoovnetnaitnypae.higher percentage of resins than The dry mix method may use powdered phenolics, phenol eresols, phenol cresol modified by linseed oil, phenol cresol modified by linseed oil and chinawood oil, or phenol cresol modified by rubber. The mixed materials are compression molded in one method of manufacture. In another method, a hopper feeds the resin to a pair of rolls that compacts the material into a continuous strip. A wire screen backing may be carried by one of the rolls and incorporated with the friction material. The formed strip is then cured in long lengths or in individual segments. ' A typical dry molded brake lining as manufac tured by one company is composed of 45 to 65% of asbestos, 12 to 25% of phenolic resin, and the balance of friction modifying agents, such as carbon black, rubber, tars, etc. In molding me mix, a weighed charge is placed in a one-cavity compression mold and subjected to a pressure of 1200 p.s.i. and a tem perature of 270 to 300 F. The charge is kept in the mold long enough to flux the resin. While still in soft form, the molded slabs are cooled to stop cure of the resin and to retain the required plasticity. The tshlaicbksnaerses.then cut to size and ground to the required The cut strips are next re-heated for 1 to 5 min. in an oven, formed to the desired radius, and cooled on a water-cooled cylinder. After forming, the linings are cured at a temperature of 325c F. for 1 to 3 hours. The last steps in the process are to drill and counter sainndktethset trhievmet. holes, ins:pect the linings, and brand The wet mix process of producing bonded fiber brake lining uses bonding materials similar to those employed in the dry mix process. The linings are subdivided into two types, one in which volatile solvents are used and a stiff, dough-like mass is ob tained, and the other in which the mixing is carried out in a wet state and where non-volatile solvents are generally employed. For stiff mixing, a dough mixer is used and the resulting mixture is cured in a mold. For wet mixing, a pulp beater, similar to the lop diagram shows the Cycleweld banded lining method that provides 1/3 more thickness then riveted fining. Bot tom diagram shows limitation imposed when lining is riveted ` r-' Av.t-w S e e '.c a * : p t <y C h r y s l e r c e e = : y s* , / ..* , W ***) iastiiiS iiiiaH U M *' P r - i ' C S A B O VE C O U R T E S Y G O O D YE AR 7 1P & R U B B E R CO , lf, C Flexible steel band applies pressure in Uni-Bond process of bonding linings, which uses a fluid resin. Dealer kit includes bonds, bond spreaders, thermometer, and asbestos gloves A/ . ` A . r.' - <-. s.:- \ V ' ' - - i f ' %!?* '' iA ... ' . y ___ ____ . i IN ' j | f .. U% - June 1949 79 kind used in the paper industry, is required, the liquid being filtered or centrifuged to form a thin sheet. This sheet is then dried and laminated to the required thickness. Bonded vs. riveied linings During the past 15 years there has been extensive experimental and commercial work done on bonding brake linings to brake shoes. Briefly, the process consists of placing a cement, such as a Buna N syn thetic rubber-phenolic resin combination, between the lining and the brake shoe, clamping them to gether, and subjecting them to heat and pressure. The advantages claimed for bonded lining over riveted lining include: 1) greater usable lining sur face and thickness because of the elimination of rivets, thus resulting in a longer lining life, 2) re duction of drum scoring because there are no rivet holes to collect abrasive material or rivets to cut the drum as the lining wears down, and 3) slightly in creased friction surface because rivet holes and chamfers on the ends of the lining are eliminated. In comparisons of bonded and riveted linings, it has been determined that bonded linings may range as high as 600% greater in shear strength than riveted linTinhgesr.e are several bonding methods 'in general use. The Permafuse method1 makes use of a special Durez phenolic resin as the bonding agent. The bonding material itself, produced by Permafuse Corp., Brooklyn, N. Y., consists of a specially pre pared strip of tape impregnated with the phenolic resin. Rolls of tape are available in widths to match standard brake linings. Strips of any desired length 1 "Phenolics, Not Rivets. Bond Biake Linings," Modern Plastics 25, 100, (Oct. 1947). Brake shoes, linings, ond bonding agent are placed in a clamping fixture in a Chevrolet sub-assembly line, prep aratory to baking process which unites lining and shoe 80 MODERN PLASTICS can be cut at the time of application. In the bonding procedure, the lining, the Permafuse tape, and the brake shoe are clamped together and heated. The thermosetting resin forms an insoluble and infusible boAnd sbeectownedenbolinndiningg amndetshhoode,. called Cycleweld--a development of Chrysler Corp,---uses an adhesive composed of a phenolic resin-elastomer combination. The lining is painted with the liquid agent, clamped to the shoe, and put in an oven at a temperature of 380 F. for 15 minutes. Such bonded lining is now in use on all Dodge Job-Rated V2 and % ton trucks and is used on the new Chrysler, Dodge, De Soto, and Plymouth passenger cars. Another method in use is the Uni-Bond process developed by The Goodyear Tire & Rubber Co., Inc., which also uses a fluid resin as the bonding agent. The bonding process is similar to that of the Cycleweld process. Reports indicate that V2 gal. of the cement will bond approximately 600 pieces of passenger car lining. The company also states that Uni-Bond has doubled the life of the lining and has eliminated approximately 90% of drum scoring. The Uni-Fuse process developed by the Asbestos Mfg. Co., Huntington, Ind., uses an adhesive com pound on both surfaces of a tape composed of natural rubber and asbestos. The rubber in the tape is re ported to provide a desirable cushion between the lining and the shoe. The bonding procedure is similar to that of the Permafuse process. Plastilock 601, a brake lining adhesive developed by The B. F. Goodrich Co., has been in use for aimost two years. Claims include a shear resistance over twice that of rivets. Another report indicates that 1949 Chevrolet passenger car nroduction has 100% bonded linings. StiM some unconverted Despite the obvious advantages of bonded linings, there are still some in the automotive industry who are unconverted. One representative of a brake lining manufacturer states that bonding adds to the final cost of installation and that it calls for an in vestment that has not been proved justified by those who favor bonded linings. He further states that there is no assurance that a resin bond will hold for an indefinite period. This manufacturer remarks that very few, if any, of the lining manufacturers have been willing to assume the responsibility in volved in recommending the bonding method. They will furnish the lining ready for bonding, but the responsibility rests with the equipment, manufac turTehrisa,nhdotwhoevseerw, hisoounsley iot.ne opinion. Bonded brake lining, as indicated by its acceptance reported above, appears to be on the verge of widely expanded use. How universal will be the application is still a moot question. Brake lining and brake equipment manu facturers have hastened to develop facilities so that jobbers and dealers will be prepared to cope with maintenance of the bonded type lining. Reports indicate that the future of the bonding process de pends largely upon the activities of the automobile manufacturers. The general public as yet knows very little about the difference between bonded and riveted lining. If the auto manufacturers should de cide to use bonding on a large scale, and should advertise it widely, there is a definite possibility that most car owners would insist that bonding be used on their re-lining jobs. Of course, whenever such a demand is built up in a given area, it will be econom ically practical for automotive jobbers and repair shop operators to enter the bonding business. In 1948 there was a total passenger car production of 3,893,079. Therefore, there were 31,144,632 pieces of brake lining manufactured for immediate installa tion with approximately another eight million sets (eight pieces of lining to a set) manufactured for replacement. A total of 7,857,378 re-lining jobs were also reported for last year. This represents an in crease of 15% over 1947 and means that approxi mately one out of every five cars on the road had a brake re-lining job during 1948. The design of today's automobiles has placed ap preciably increased heat loads on brake linings. Faster driving speeds, smaller brake drums, and in creased shrouding of wheels necessitate linings of greater heat stability and better wear resistance. The significance of this trend is evidenced in the demand for better heat-resistant phenolic or modi fied phenolic resins combining good frictional prop\ erties. Today, the resin industry is said to be working on new resins that will withstand temperatures be tween 650 and 800 F. for a greater period of time. Present resins carbonize and disintegrate too rapidly j at temperatures above 700 F. If better resins can be developed, brake lining life will be greatly in creased, it will be possible to operate automobiles at higher speeds with greater safety, and the cost of brakes per mile of motor car operation will be appre ciably lowered. Acknowledgements Modern Plastics wishes to thank the following for their assistance in the preparation of this article: James W. Lee II, Chrysler Corp., Detroit, Mich.; C. Rector, National Engineering Products, Inc., Washington, D. C.; Paul C. Kenyon, The Goodyear Tire & Rubber Co., Inc., Akron, Ohio; Thomas L. Gatke, Gatke Corp., Chicago, 111.; S. Pudlin, Triple wear, Inc., Newark, N. J.; C. Allan Lafferty, Auto motive Industries, Philadelphia, Pa.; Donald H. Spicer, World Bestos Corp., New Castle, Ind.; J. A. Scott, Marshall-Eclipse Div., Bendix Aviation Corp., Troy, N. Y.; H. Gelband, National Brake Block Corp., New York, N. Y.; S. E. Shepard, Asbestos Mfg. Co., Huntington, Ind.; S. R. Zimmerman, Jr. and Franklin A. Miller, Raybestos-Manhattan, COURTESY fAE JOURNAL- In one type of bonded broke lining the cement is eppiied in narrow strips at the edges. A cleaned brake shoe is at right C O U R T E S Y J O H N S MAH V t L l E Linings of any desired width and length may be cut from heavy duty woven sheet. Woven linings do not fray when cut Inc., New York, N. Y.; J. A. Ahlers, Automo tive Digest, Cincinnati, Ohio; Howard Snow, Southern Friction Materials Co., Charlotte, N. C.; Clark R. Simmons, Durez Plastics & Chemicals, Inc., North Tonawanda, N. Y.; E. E. Novotny, Chemical Div., The Borden Co., Philadelphia, Pa.; E. H. Wells and Eldredge Miller, Johns-Manville, New York. N. Y.; H. C. Morton, and Gustav Walters, The Russell Mfg. Co., Middletown, Conn.; John R. Heath, Grizzly Mfg. Co., Paulding, Ohio; D. Reddy, Motor, New York, N. Y.; Donald Masson and E. H. Gross. Baklite Corp., New York, N. Y.; Leslie Peat, SAE Journal, New York, N. Y.; W. R. Rodger and J. V. Hendrick, Chrysler Corp., authors of "Bond ing Brake Lining to Shoes;" John McLaine, Thermoid Co., Trenton, N. J.; Roger B. Stafford, Super Service Station, Cleveland, Ohio; and Joseph H. Karshnar, General Motors Corp., Detroit, Mich. June 1949 81