Automotive seal types

The concept of two or even three extruders in tandem, or piggy back , feeding to a common die to produce such items as tyre camelback are available from a number of producers. The machines are used to produce components having either different layers or sections consisting of a number of different compounds. Applications using this type of system are tyre components and automotive sealing profiles. 

Another dynamic seal type used is the poly(tetrafluoroethylene) (PTFE) seal utilized on applications with PV values that are not as stringent as those of clutch systems. PTFE is a fluoropolymer that has many other applications besides automotive. DuPont has the trade name Teflon for this material. Other usages include nonstick cookware, lubricants, bearings, bushings, gears, and plumbing materials. It is useful as a resistant material to corrosive and reactive chemicals. It is an extremely nonreactive material that was discovered by accident by Roy Plunkett when he... 

Typically, a 50/50 blend of nitrile rubber and polypropylene is melt mixed with 5 % maleated PP and 1 % ATBN respectively and then cured with SnCl2 (0.5 %). The resistance to hot oil swell (72 h, 100 °C) of NBR/PP blend was found to be significantly better than that of EPDM/PP blend. Typical properties of the commercial dynamically cured NBR/PP TPV (Geolast ) are compared with other PP-based TPVs in Table 19.16. Commercial applications for this TPV were targeted for automotive seals and gaskets in the oil, fuel, and brake systems. However, this blend has not been as commercially successful as the Santoprene -type PP/EPDM-based TPV. 

Whereas automotive batteries have the majority of the market, other types of lead—acid batteries, such as sealed and small maintenance-free varieties, are making inroads into various appHcations. The automotive battery s operating environment has changed substantially in the last 10 years. Underhood temperature has risen and electrical loads have increased. This trend is expected to continue as car manufacturers reevaluate thek design strategies and objectives. Battery design is changing to meet these needs. 

Lead-acid batteries can be classified into three major types or categories, namely, automotive (SLI), stationary, and motive power (industrial). In addition, there are many special batteries that cannot be easily categorized as either of the above types. As these types of batteries are constructed with different materials and design to meet the requirements of their intended end uses, each requires a particular separator with specific material composition, mechanical design, and physical, chemical, and electrochemical properties that are tailored for the battery and its relevant specific uses. These batteries are generally available in flooded electrolyte or valve regulated (sealed) versions. In this section the types... 

Sealing electrical bushings and terminals. Used instead of silicone oils in vacuum pumps. May have been added to automotive transmission oils to swell shrunken transmission seals in place. Ingredient in emulsifiable-type cuttings oils to increase heat resistance (Monsanto, 1960). 

Numerous seal designs are available to the automotive chemist. Choices are made depending on the application and sealing requirements. Figure 8.16 shows a few of the types of seal designs used. 

The types of rubber for the automotive industry can be considered in two groups tyres (mostly of NR, SBR, polybutadiene and butyl type rubbers), and profiles and seals (for profiles nitrile-butadiene rubber and derivatives, acrylates, fluoro-rubbers and silicones for sealing). 

The new elastomers are particularly relevant to the automotive industry because they offer better properties - particularly heat, oil and fuel resistance - than the established materials such as natural and synthetic rubber and plasticized PVC. Among the most important types are PUR elastomers, PBT block copolymers, EPDM olefinic terpolymers and ethylene-acrylic elastomers. Typical applications are the traditional rubbery ones of gaskets, seals, gaiters and cable covers, but set in the aggressive underbonnet environment of today s performance vehicles. Beyond this, however, there are examples where these materials are sufficiently versatile to have been selected, sometimes with reinforcement, as engineering components in their own right. 

The main applications for these types of polymer are in automotive fuel hoses, pump seals, power steering units and transmission gaskets. 

For high-volume automotive-type batteries, the fabrication process was substantially modified with the introduction of the PE separator and its two unique properties flexibility and weldability. Unlike previous separators, the PE separator could be wound onto a roll and could be completely wrapped around the plate without breaking and cracking. Additionally, the PE separator was weldable unto itself either by sonic, mechanical, or heat welding. These two properties opened up the opportunity for further assembly optimization of which the equipment suppliers soon advanced the technology to meet the need [34]. The assanbly equipment automatically wraps a separator around the bottom of the PE separator and then mechanically seals the sides to create a three-sided pocket around the plate. This pocket minimizes the potential for bottom and side shorts. 

The worldwide secondary battery market is now approximately 20 bilhon annually. A world perspective of the use of secondary hatteries by application is presented in Table 22.1. The lead-acid battery is by far the most popular, with the SLI battery accounting for a major share of the market. This share is declining gradually, due to increasing apphcations for other types of batteries. The market share of the alkaline battery systems is about 25%. A major growth area has been the non-automotive consumer applications for small secondary batteries. Lithium ion batteries have emerged in the last decade to capture a 50% share of the market for small sealed consumer hatteries, as indicated in Table 22.1. The typical characteristics and applications of secondary batteries are summarized in Table 22.2. 

Applications for lead-acid batteries, other than the SLI and small sealed power units, fall into two categories, as shown in Table 23.22—those based on automotive-type constructions and those based on industrial-type constructions. Often several designs can be used for a single type of application. 

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. 

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