Document zv1KgQoQOMzDmQzM8ZwnYea3

FILE NAME: Dana (DAN) DATE: 1980 July DOC#: DAN009 DOCUMENT DESCRIPTION: Trade Journal Article - "What Will Replace Asbestos Gaskets?"  f/'* What Will Replace Asbestos Gaskets? By John E. Zeitz REPRINTED FROM July 1980 V P D -142-0002632 What Will Replace Asbestos Gaskets? By John E. Zeitz GASKET suppliers and gasket material pro ducers have been working for several years on programs 1o develop asbestos-free gasket materials for use in all the sealing needs ol vehicular and industrial applications. And the tempo ol this development is increasing. Asbestos has been an important part of gas ket materials since the advent of the internal combustion engine. It has a number of good characteristics, and has been used extensive ly. These good characteristics are the physi cal properties of asbestos, such as high heat resistance, excellent crush resistance, dimentional stability, and the ability to be pro duced into a homogeneous product. The ability to produce a homogeneous prod uct is greatly aided by the material's high sur face area per unit weight, a factor as high as 60 sq. ft./gram (5.6 m'/gram). Added to these physical properties, relatively low cost and ease ot processing must be included among Ihe advantages ol asbestos. JPorhonduEc.tsZDenivzisisiodnivoisfiDononcahiCefoerpnogrinaetieorno. r the Victor However, there are a number of disadvan tages with the material. First, there is growing emphasis on costly preventive health and control substance programs required lor those handling the materials. There is also a growing belief on the part ol influential users and producers of asbestos products, as well as outside groups, that the use ol asbestos in automotive and other vehicles should be cur tailed. The cost of company-wide health programs and controlling the environment in which as bestos is handled is causing many to seek al ternatives to using the product. One problem lor all suppliers and users ol asbestos prod ucts is how the end user disposes of the prod uct. In the gasket business this is a parti cularly sensitive area because often the end user finds himself using a wire brush or scrap er to scrape asbestos oil of an engine part to clean up residue gasketing. Untortunately, it is the asbestos you cannot see that finds its way into the lungs So unless special preventive health procedures are fol lowed, the end user of asbestos gaskets may be in more potential danger than the person nel in the producer's facility. This could be particularly true in large volume engine re build operations. Government regulatory agencies are keenly interested in seeing asbestos usage curtailed, or eliminated from industrial and commercial products. Though no timetables have been set, it is very likely a special license or waiver will be needed as early as 1985. And, by 1990, the use ol asbestos may not be permitted under any circumstances. It may be that government regulations alone may eventually force the elimination of all as bestos from areas where it is now used -- in cluding gaskets. The number ol regulatory agencies controlling asbestos continues to grow. There are primarily six federal agencies concerned with asbestos. There are the Envir onmental Protection Agency (EPA). the De partment ol Transportation (DOT), the Con sumer Protection Safety Commission (CPSC), the Mine Safety Health Administration (MSHA), the Occupational Satety and Health Administration (OSHA), and the Food and Drug Administration (FDA) Among these six agencies, approximately 20 regulations have been promulgated to control Y P D -1 4 2 -0002633 exposure of asbestos from various sources. Added to these are the many international and state regulations, and the regulatory sit uation is ceilatnly challenging Another disadvantage ol asbestos is its scar city Compared to oil, the U.S. is more com pletely dependent on foreign sources for as bestos than it is tor petroleum Although gen eral asbestos supplies seem adequate, the long grades such as number 4 and 5 fiber lengths used extensively for gasket materials have been in tight supply lor the past lour years The Imal disadvantage of asbestos is that it does not always solve all the problems that it is asked to solve In short, better heat resis tance sealability and crush resistance are often required Asbestos has served us well and will continue to do so but there are more and more demands tor better solutions At present, the majority of gaskets in the U.S. do contain asbestos. Most of them contain 80% asbestos in their composition with the rest being polymer binder systems and fillers. The problem of replacing asbestos is of very large magnitude. However, before we get Into reviewing what is being done to replace as bestos, we should probably consider what the asbestos suppliers are currently saying about the situation They state very simply, that once the material reaches the consumer, the asbestos is tocked-in by the various pro cesses used in manulacture. Granted, this may be true, but it is very difficult for most gasket suppliers to verify that this condition continues throughout the use of the product when they consider the asbestos-contained material is typically sheared, torn, calender ed, scraped, sanded, punched, burned, form ed, compressed, and ground in its further manufacture and use as a gasket. Because of the disadvantages mentioned and the lack of technical ve'rification of the safety of the material when processed and usdcf as gasketing, several major domestic users have embarked upon programs to eliminate asbes tos gaskets from their product lines. Let's ex amine what asbestos-free materials will have lo do when they replace asbestos products in gaskets Replacement materials will have to have high-heat resis lance, excellent cwsh re sistance, dimentional stability, and homogen eity As another reference point, we should examine those products currently available in the marketplace. These are cellulose, anaero bics, RTV, and rubber-coated steel. A number of companies have eliminated as bestos gasketing, and gaskets In general, from their current assemblies. The General Motors Corporate V-6 has only two gasket ap plications in the engine: the cylinder head gasket and the Intake mamlold gasket. Both of these applications are with asbestos con taining materials. Many transmission manu facturers are also eliminating gaskets from their assemblies and replacing Ihem with li quid sealant to reduce the tolerances requir ed for assembly. This permits them to develop quieter-running transmissions and gear boxes -- another upcoming regulation Asbestos seems to be used in the majority of cylinder head applications and intake mani fold applications, exhaust manilold applica tions, and a large number ol extremely heavi ly loaded llanges. However, the critical re quirements of these various applications are not the same from application to application Cylinder head and intake manilold applica Anaerobic and other liquid sealants are one way to solve the problem of eliminating asbestos from many sealing prod ucts. Shown here 15 a 28 in. long housing with a liquid gasket seat ready for assembly tions require materials having good homogen eity and the resulting contormability that per mits a good fluid seal. Exhaust manifold appli cations require the high-heat resistance char acteristics of asbestos and heavily loaded flanges require the crush and extrusion resis tance of asbestos. So it is possible to replace asbestos in different ways for different ap plications More Importantly, it appears that If we could Improve certain properties in certain applications, we could present design engi neers and the marketplace with an improved product with greater appeal For years gasket material producers and de signers have attempted lo improve the binder systems in gaskets. This work was done be cause the binder system appeared to be the limiting ingredient in gasket functional design. Little was done to improve the fiber charac teristics and to obtain increased functional characteristics through this method. We are now looking at that 80% of the gasket which represents the fiber to see what can be done in replacing asbestos to improve its lunctional characteristics. However, to do this, one quickly finds that no single man-made fiber or other high temperature material approaches asbestos in its crucial physical properties. II is therefore necessary to blend materials to obtain the desired properties. The types of materials blended are mainly various fibers and fillers, although rubber coated steel is also considered an alternative. Clay is one such filler. It is inexpensive, com pressible in bulk, and fills the voids between the larger fibers of glass, nylon, or aramid Clays are easily dispersed in mixtures of water From a sealing point of view, the clay reduces the spring rale of the facing, and im proves the load bearing capabilities Temper ature resistance is above 3000 F (1649 C). Clay, when added lo most materials, in creases the surface area to the magnitude of asbestos. Clay has better conformabrlity pro perties than asbesetos. Mica is basically a tiller, also, and has been used lor years in the paper industry Vermicu lite is the thermal or chemically expanded lorm of mica which is very economical, has high surface area, and good temperature re sistance (above 2000 F) It has relatively low strength, but good slip characteristics, caus ed by the low coelficient of friction of the par ticle Mica has belter torque and heat resis tant properties than asbestos. Graphite has the highest heat resistance of the materials presently under consideration with the tensile strength increasing until 4000 F and heat resistant above 5000 F. The mater ial is very costly but can be used in layers. The unique low friclional characteristics of the platelets help where motion is a problem. Glass fiber is another candidate. It normally endures heat lo 1100 F, where softening and fusing takes place However, it has good strength and the thinnest diameter or highest surface area of any man-made fiber. It will be used to reinforce mica, clay or barytes based compounds in the same way as aramids and nylons will be used. In some applications cellulose fiber may be favored But it is used very sparingly, if at all. in materials requiring high temperature resis tance because of its low charring tempera ture In applications where heal is not above 300 F, however, the liber can be used as a successful earner web or matrix for a variety ol fillers VPD-142-0002634 Organic fibers also have potential Aramids such as Kevlar and polyamides such as Nomex are examples ot current organic fi bers. These fibers have tremendous tensile strength and modulus, and yet some grades are relalively flexible. Although ihese mater ials begin degrading at 500 F, they do not dis integrate or gasify and at 2000 F have higher strength than asbestos and are being used in compounds in small quantities. High strength or engineering ceramics have possibilities, too, although there are technical problems on how the ceramic fibers are bond ed together. Ceramics are typically metal ox ides, nitrides, or carbides and have a temper ature range of up to 3000 F, and compressive strength which is more than twice that of as bestos. At these temperatures the binder sys tems disintegrate and it is necessary to still keep the ceramic together. In addition, cera mic fibers are 30 times the diameter of asbeslos, so homogeneity is a problem; but for high temperature exhaust gas applications this Is an acceptable'alternative when blended with other fibers. Coated metals will also find a niche. They have the physical strength o1 the substrate metals coated with a well bonded yet embossable sealing coating of nitrile or silicone. There is no wicking because of the solid steel barrier as well as good relaxation properties and good extrusion properties. As a result of current programs, we can pre dict that in exhaust and turbocharger applica tions, graphite, ceramic fibers and fillers, and mica, combined with stainless steel sub strates, will be popular materials. For cylinder head and intake manifold applications, we see the use of organic fibers and binders and inorganic fillers formed by a paper making process and also combined to metal sub strates. Embossed steel or aluminum with high temperature coatings will continue to be used where engine structure permits. In high load and high extrusion gasket appli cations, the most prevalent materials will be rubber coated steel, cellulose fibers wilh elas tomeric binders, glass fiber with fillers and elastomeric binders, densitied organic libers and fillers with elastomeric binders, and liquid systems such as RTVs and anarobies The final cost of non-asbestos materials is still not resolved. Material suppliers have been given a target ot less than two times what we are paying for malerial today and most feel comfortable wilh this. Since the asbestos-free material makes up onfy a portion of the gas ket's cost, the total selling price should be sig nificantly less than twice current pricing. In the long term, it is expected that asbestosIree products with improved properties will sell for no more than current products -- cer tainly on a lotal engine package basis. The trick to replacing asbeslos is lo blend the fibers and fillers and polymers to reduce the cost and optimize the physical and chemical properties using multivariable analysis. And the initial results look excellent. Currently, as bestos tree versions of Victor's popular Victocor, Solicor, Victopac, Corbestos, and Coramic materials are being sampled and tested by O.E. diesel and gasoline manufacturers in the U.S. and abroad and compare favorably in performance to existing materials. The cur rent price structure is considered attractive. V P D -142-0002635 Prinled n U.5-A