Document 15MMYxKb6v3YjmVaYYb6Je1Od

What Will Replace Asbestos Gaskets? By John E. Zeitz REPRINTED FROM July 1980 DIESEL& gAs5bbin1! DANA-0326.60 VPD. 142-0002632 What Will Replace Asbestos Gaskets? By John E. Zeitz BASKET suppliers and gasket material pro ducers have been working lor several years on programs to develop asbestos-free gasket materials tor use in all the sealing needs ol vehicular and industrial applications. And Ihe tempo ot this development is increasing. Asbestos has been an important part of gas ket materials since Ihe advent ol Ihe internal combustion engine. II has a number ol good characteristics, and has been used extensive ly. These good characteristics are Ihe 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 (actor as high as 60 sq. It./gram (5.6 m'lgtam). Added to these physical properties, relatively low cost and ease ol processing must be included among the advantages ol asbestos. John . Ztiiz is division chief engineer oi ihe Victor Products Division of Dona Corporation. However, there are a number ol disadvan tages with the material. First, there is growing emphasis on cosily preventive health and control substance programs required tor Ihose handling the materials. There is also a growing belief on the part oi influential users and producers ol 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 ptoducts is how the end user disposes ol the prod uct. tn the gasket business this is a parti cularly sensitive area because olten th^ end user finds himself using a wire brush or scrap er to scrape asbestos oft of an engine part to clean up residue gasketing. Unfortunately, it is the asbestos you cannot see thal finds its way into the lungs. So unless special preventive health procedures ate lotlowed. the end user ot asbestos gaskets may be in more potential danger than the person nel in the producer's lacility. 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 wilt be needed as early as 1985. And. by 1990. the use ot asbestos may not be permitted under any circumstances. It may be thal government regulations alone may eventually force Ihe elimination ol 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 Ihe Envir onmental Protection Agency (EPA), the De partment ol Transportation (DOT), the Con sumer Protection Safety Commission (CPSC), the Mine Salely Health Administration (MSHA). the Occupational Safety and Health Administration (OSHA), and Ihe Food and Drug Administration (FDA). Among these six agencies, approximately 20 regulations have been promulgated to control VPD-142-0002633 exposure ot asbestos Irom various sources. Added to these are the many international and state regulations, and the regulatory sit uation is cerrainly challenging. Another disadvantage ol asbestos is its scar city. Compared to oil. (he U.S. is more com pletely dependent on loreign sources lot as bestos than it is lor petroleum. Although gen eral asbeslos supplies seem adequate, the long grades such as number 4 and 5 liber lengths used extensively for gasket materials have been in light supply loi the past lour years. The final disadvantage ol asbeslos Is that it does not always solve all the problems that il is asked lo solve In short, better heat resis tance sealabilily and crush resistance are olten requited. Asbestos has served us well and will continue to do so but there are more and more demands lot belter solutions. At present, the majority ol gaskets in the U.S. do contain asbestos. Most ol them contain 80% asbestos in Iheir composition with the rest being polymer binder systems and tillers. The problem ot replacing asbestos Is ol very large magnitude. However, before we gel inlo reviewing what is being done to replace as beslos, we should probably consider what the asbeslos suppliers are currently saying about Ihe situation. They stale very simply, that once the material reaches the consumer, the asbestos is locked-in by Ihe various pro cesses used in manutactuie. Granted, this may be hue. but il is very difficult lor most gasket suppliers to verily that this condition continues throughout the use ol Ihe product when they consider Ihe 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 cl the disadvantages mentioned and Ihe lack ol technical verification of the safely of the material when processed and usStf as gasketing, several major domestic users have embarked upon programs to eliminate asbes tos gaskets horn their product lines. Let's ex amine what asbestos-free materials will have lo do when they replace asbeslos pioducts in gaskets. Replacement materials will have to have high-heat resistance, excellent crush re sistance, dimenlional stability, and homogen eity. As another reference point, we should examine those products currently available in the marketplace. These are cellulose, anaerobics, RTV. and rubber-coaled steel. A number ol companies have eliminated as bestos gasketing, and gaskets in general, Irom their current assemblies. The General Motors Corporate V-6 has only two gasket ap plications in ihe engine: Ihe cylinder head gasket and the intake manifold gasket. Both ol these applications are with asbeslos con taining materials. Many transmission manu facturers are also eliminating gaskets from their assemblies and replacing them with li quid sealant lo reduce the tolerances requir ed lor assembly. This permits them to develop quietei-running transmissions and gear boxes -- another upcoming regulation Asbeslos seems to be used in the majority ot cylinder head applications and intake mani fold applications, exhaust manilotd applica tions. and a large number of extremely heavi ly loaded flanges. However, Ihe critical re QUirements ol these various applications are not the same from application to application. Cylinder head and intake manifold applica tions require materials having good homogen eity and the resulting conlormabllliy that per mits a good fluid seal. Exhaust manifold appli cations require the high-heat resistance char acteristics ot asbestos and heavily loaded flanges require the crush and extrusion resis tance of asbestos. So il is possible to replace asbestos in different ways lor different ap plications. More importantly, it appears that il we could Improve certain properties in certain applications, we could present design engi neers and the marketplace with an impioved product with greater appeal. For years gasket material producers and de signers have attempted to 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 liber charac teristics and to obtain increased functional characteristics through this method. We are now looking at that 80% ot the gasket which represents the liber to see what can be done in replacing asbestos to improve its lunclional characteristics. However, to do this, one quickly finds that no single man-made fiber or Other high temperature material approaches asbeslos in its crucial physical properties. It is therefore necessary to blend materials to obtain the desired properties. The types ot materials blended are mainly various fibers and fillers, although rubber coaled steel is also considered an alternative. Clay is one such tiller, il is inexpensive, com pressible in bulk, and fills the voids between the larger libers of glass, nylon, or aramid. Clays are easily dispersed in mixtures ol water. From a sealing point ol view, the day reduces the spring rale ol 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 lo Ihe magnitude ol asbestos. Clay has better conlormabllity pro perties than asbesetos. Mica is basically a filler, also, and has been used for years in the paper industry. Vermicutile is the thermal or chemically expanded lorm ol mica which is very economical, has high surface area, and good temperature re sistance (above 3000 F). II has relatively low strength, but good slip characteristics, caus ed by the low coellicienl ot friction ol the par ticle. Mica has better torque and heat resis tant properties than asbeslos. Graphite has the highest heat resistance ol the materials presently under consideration with the tensile strength increasing until 4000 F and heat resistant above 5000 F. Thp mater ial is very costly but can be used in layers. The unique low frictional characteristics ol Ihe platelets help where motion is a problem. Glass fiber is another candidate. It normally endures heal to 1100 F, where softening and fusing takes place. However, it has good strength and Ihe thinnest diameter or highest - surface area ol any man-made liber. Il will be used to reinlorce mica, clay or barytes based compounds in the same way as aramids and nylons will be used. In some applications cellulose liber may be favored. But it is used very sparingly, if at all, in materials requiring high temperature resis tance because ol its low charring tempera ture. In applications where heat is not above 300 F. however, the liber can be used as a successful carrier web or matrix lor a variety of fillers. VPD-142-0002634 Organic libers also have potential. Aramids such as Kevlar and polyamides such as Nomex are examples of current organic fi bers. These libers have tremendous tensile strength and modulus, and yet some grades are relatively flexible. Allhough these 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 libers are bond ed together. Ceramics are typically metal ox ides, nitrides, or carbides and have a temper ature range ol up to 3000 F. and compressive strength which is more than twice that ol as bestos At these temperatures the binder sys tems disintegrate and ft is necessary to still keep the ceramic together. In addition, cera mic libers are 30 times the diameter of asbes tos, so homogeneity is a problem; but tor high temperature exhaust gas applications this Is an acceptable'altemative when blended with other libers. Coated metals will also tind a niche. They have the physical strength ot the substrate metals coated with a well bonded yet embossabte sealing coating ol 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 libers and tillers, 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 libers 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 coaled steel, cellulose fibers with elas tomeric binders, glass liber with Tillers and elastomeric binders, densified organic libers and tillers with elastomeric binders, and liquid systems such as RTVs and anaerobics. The tinal cost ol non-asbestos materials is still not resolved. Material suppliers have been given a large! of less than two times what we are paying for material loday and most teel comfortable with this. Since the asbestos-free material makBs up only a portion of the gas ket's cost, the total selling price shouldbe sig nificantly less than twice current pricing, in lha long term. It is expected that asbestosfree products with improved properties will sell lor no more than current products -- cer tainly on a total engine package basis. The tifck to replacing asbestos is to blend the libers 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 free versions of Victor's popular Victocor, Sollcor. Victopac, Corbestos, and Cera mic 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. j ! ! i i' VPD-142-000263 5 Prmttd In U.S.A.