Automotive seal processing

As a result of its saturated polymer backbone, EPDM is more resistant to oxygen, ozone, UV and heat than the low-cost commodity polydiene rubbers, such as natural rubber (NR), polybutadiene rubber (BR) and styrene-butadiene rubber (SBR). Therefore, the main use of EPD(M) is in outdoor applications, such as automotive sealing systems, window seals and roof sheeting, and in under-the-hood applications, such as coolant hoses. The main drawback of EPDM is its poor resistance to swelling in apolar fluids such as oil, making it inferior to high-performance elastomers, such as fluoro, acrylate and silicone elastomers in that respect. Over the last decade thermoplastic vulcanisates, produced via dynamic vulcanisation of blends of polypropylene (PP) and EPDM, have been commercialised, combining thermoplastic processability with rubber elasticity [8, 9]. 

Figure 9 shows the typical seams to be sealed on an automotive chassis. This sealing process is normally found in an area in the plant known as the paint shop. The sealant material is applied immediately, prior to topcoat paint processes. The ensuing paint ovens then cure both the paint and sealant. 

Typically, sealant materials used to protect electronic components in aerospace automotive and appliance equipment are acrylics, silicones, urethanes, polysulfides, epoxies, and unsaturated polyesters. Liquid forms of these materials can he irreversihly converted to the sohd form with no significant weight loss. These types of sealing processes are called potting and encapsulating. 

Parts made from fluoroelastomers ate used ia appHcations that justify their high cost, usually where the maintenance and replacement costs are high enough to offset the initial cost of the part. These include automotive appHcations such as valve stem seals, fuel injector components, radiator, crankcase and transmission seals, and carburetor needle tips. Numerous seals and gaskets in the marine, oilfield, and chemical processing industries employ fluoroelastomers. In addition, many hoses in the automotive and chemical industry are made entirely of fluoroelastomer compounds or have a veneer of the fluoroelastomer as a barrier exposed to the harsh environment. Seals and gaskets in military appHcations and the binder for flares and missile appHcations ate made with fluoroelastomers. 

The excellent properties of these fluoroelastomers come with a high price tag. Kalrez, for example, is extremely expensive ( 33—44/kg). These materials are used in automotive appHcations (seals, gaskets, fuel hose lines, engine parts, etc), where they can withstand under-hood temperatures. They are also used in equipment for oil and gas production and chemical processing. U.S. consumption in 1988 was 3100 t (76). 

New polymer structures allow the control of processability and final characteristics. For example, Mitsui is launching nanostructured metallocene alpha-olefins that have a crystallite size of the order of nanometres instead of microns as for conventional metallocene polyolefins. This yields a better balance of transparency, heat resistance, flexibility and elasticity characteristics. Targeted applications are automotive interior trim, packaging film, construction materials, protective films for electronic and optical parts, sealing products and as polymer modifiers. 

The U.S. rubber processing industry encompasses a wide variety of production activities ranging from polymerization reactions closely aligned with the chemical processing industry to the extrusion of automotive window sealing strips. The industry is regulated by seven Standard Industrial Classification (SIC) codes [1] ... 

A study was made of relationships between compound rheological properties, microwave vulcanisation parameters and accelerators on the quality of extruded EPDM foam seals for the automotive industry. The influence of these factors on cell size and structure, density and mechanical properties was investigated. Correlations were found between the chemical composition of the compound, variations in processing parameters and the quality of the finished product. 12 refs. 

Polybenzimidazoles have been used for seals, mechanical components, electrical connectors, valve scats, and as components ofmatcrials-handling equipment in the petrochemical, geothermal, chemical process, aerospace, defense, automotive, and electrical products industries. These materials frequently are procured as replacement parts for other materials in an effort to improve equipment performance. 

Ethylenethiourea has a wide variety of uses in addition to vulcanization, a principal application since 1948. The curing process converts most of the ETU to other compounds, but traces of it are still found in the rubbers. Neoprene (polychloroprene) is found largely in automotive parts, wire and cable insulation, construction and adhesives. Consumer products containing neoprenes include container seals (e.g., aerosol dispensers) and shoes. It is also an intermediate in the manufacture of antioxidants, dyes, fungicides, insecticides, pharmaceuticals, synthetic resins, and a constituent of plating baths. 

Thermoplastic polyurethane elastomers are processed by injection molding and other processes used for thermoplastics. Small gears, seals, and even automotive fender extensions can be produced by this means. 

With the high-temperature solution polymerization processes, various ethylene homo- and copolymers with different average molecular mass and copolymer compositions are produced. The product portfolio comprises PE-HD, PE-LLD, PE-VLD, and the ethylene/propylene elastomers (EPM, EPDM) (see Figure 2). The thermoplastic products have a wide range of applications [1]. The elastomeric ethylene/propylene copolymers can also be applied widely in the automotive industry, for plastics modification, in industrial applications such as seals, in electrical cables, and in tires [2], Uncured ethylene/propylene copolymers are applicable as viscosity index improvers for lubricant oils [5]. 

Fig. 7.8.7 shows the development steps of the Bosch camera module. A stereo video camera for automotive application can be produced as a compact unit to be mounted at the upper rim of the front window of the car. Fig. 7.8.8 shows the unit. It consists of two camera heads with a nonlinear CMOS sensor each, and the camera optics, both mounted into a housing, which can be hermetically sealed. The camera heads are connected to a powerful computer for image processing. The power required depends on the functions. 

Automotive Office Equipment Low coefficient of friction Good mechanical properties Cryogenic properties Chemical resistance Seals and rings in automotive power steering, transmission, and air-conditioning. Copier roller and food processing equipment covering. 

In the automotive, office equipment, and other industries, the mechanical properties of fluoropolymers are beneficial in low-friction bearings and seals that resist attack by hydrocarbons and other fluids. In food processing, the Food and Drug Administration (FDA) has approved fluoropolymer grades as fabrication material for equipment due to their resistance to oil and cleaning materials, and their anti-stick and low friction properties. 

Nearly all of the dynamically vulcanized EPDM/PP blend s (Santoprene ) growth has been at the expense of thermosetting rubbers due to the blend s easy melt processability and recyclability. Much of this growth has been in automotive applications such as rack and pinion steering boots, seat belt sleeves, and air ducts. EPDM/PP blend has also been used in window and door glazing seals, weather stripping and extrusion applications in the electricaE electronic industry. 

Thermoplastic PAI resins find use in many applications, such as adhesives, coatings, filled and unfilled molding compositions, fibers, films, composites, and laminates. In particular they are used in aircraft, automotive electric and electronic appUcations, as coatings, seals, and in oil and gas processing equipment. 

Uses Chlorosulfonated PE in jacketing and insulation tor wire/cable, soles and heels, automotive components, coated fabrics, wh. tire sidewalls, sheet rooting liners and covers for reservoirs and waste containment ponds, protective and decorative coatings, hose, linings for chemicals processing equipment, industrial rolls, seals, gaskets, and diaphragms Features n. elastomer resist, to weather, ozone, oil, soivs., chemicals, heat, flame, and abrasion Properties Wh. chips. 

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