Automotive seal

Vluorosilicone. By fluorinating the siHcone polymer molecule it is possible to improve the solvent, fuel, and oil resistance of this already heat-resistant class of elastomers. The resulting polymers are especially useful in select automotive seals and gaskets as weU as military and downhole oilfield parts. 

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. 

TPV applications are mainly in automotive seals and pipe seals where a good compression set and heat resistance are required. 

Textiles Coatings (e.g., back coatings, impregnation, carpets, automotive sealing, furniture ri homes and office buildings, aircraft, subways, tents, trains, and military safety clothing) ... 

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]. 

MAJOR PRODUCT APPLICATIONS electrical connectors, automotive components, automotive fascia, automotive seals, gaskets and bearings, aerospace components, friction products, putty compounds, adhesives... 

An automotive seal, for instance, must be efficient that is, it must have the ability to expand against a sealing surface quickly. This efficiency is related to the elastic modulus of the material, which is related to its stiffness [1], The elastic modulus is the ratio of stress to corresponding strain in a material below the proportional limit on a... 

The thermal serviceability or usage range is the temperature range in which a sealing material can be used and expected to function without degradation of properties. Table 8.1 shows the ranges of some compounds typically used in automotive sealing. 

The mechanism responsible for the hardening of hydrogenated nitrile rubber automotive seal compounds on prolonged exposure to automatic transmission fluids at high temperature was investigated. The increase in hardness was found to result primarily from chemical attack at the acrylonitrile sites. This chemical attack first resulted in the formation of isocyanide or isonitrile ions. The proposed mechanism involved crosslinking at the acrylonitrile sites through the formation of isonitrile ions and the subsequent formation of imides. 

TPV market is primarily in automotive sealing where TPVs are displacing EPDM in less demanding (e.g., static) molded window seals. However, compression set remains an issue in more demanding (e.g., dynamic) applications such as door seals. TPVs are also increasingly used in overmolding on engineering plastics to achieve soft-touch tactile feel to the molded parts. 

Automotive seals and weather stripping for windows, hoods, trunks, doors, sun roofs, handle gaskets, window spacers, window guides, lcx k seals, windshield... 

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. 

Acrylic rubber can be emulsion- and suspension-polymerized from acrylic esters such as ethyl, butyl, and/or methoxyethyl acetate to produce polymers of ethyl acetate and copolymers of ethyl, butyl, and methoxyl acetate. Polyacrylate rubber, such as Acron from Cancarb Ltd., Alberta, Canada, possesses heat resistance and oil resistance between nitrile and silicone rubbers. Acrylic rubbers retain properties in the presence of hot oils and other automotive fluids, and resist softening or cracking when exposed to air up to 392°F (200°C). The copolymers retain flexibility down to -40°F (-40°C). Automotive seals and gaskets comprise a major market. These properties and inherent ozone resistance are largely due to the polymer s saturated backbone (see Table 3.13). 

Automotive seals and gaskets in hot oil applications comprise a major market for these materials. Acrylic rubbers can be compounded in a Banbury mixer and fabricated by injection molding, compression molding, resin transfer molding, extrusion, and calendering. 

Important applications of calcium carbonate in the rubber industry include use in electrical wire and cable insulation where the low moisture content and natural insulating properties make it a preferred filler, in the production of articles where low cost and smooth surface appearance are desired, such as footwear, and in extruded hoses and automotive sealing parts. 

Among the specific challenges for the automotive seals and gasket industry are ... 

Table 3. Typical Automotive Sealing Adhesives. (Sealers and Gaskets)...

Carboxylated nitrile rubber (XNBR) has better abrasion resistance than regular NBR. Their applications are automotive seals, industrial footwear, mechanical goods, textile spinning cots, adhesives, packings, flat drive belting, hoses, industrial wheels, oil well specialties, and roll covers. 

P.E. Manley, New Technology for Polyacrylic Elastomers in Automotive Sealing Applications, SAE Meeting, Detroit, February 26-29, 1996. 

Multi-shot moulding techniques are well established, their growth being pushed by the development of thermoplastic elastomer (TPE) materials, enabling rigid and flexible material combinations such as those described previously to be employed. These can also be seen in a variety of other applications from automotive seals to bras. 

HOW TPV OUT-PERFORMS EPDM IN ACOUSTIC PROPERTIES FOR AUTOMOTIVE SEALING.900... 

---