Vibration dampening applications

Sealing in an automobile is most vital and a chemist s skills are quite useful. Just as vital however, is the isolation and vibration dampening application of rubbers thus, some discussion time should be devoted to this subject. Most mechanical engineers and computer analysts do not have a working knowledge of rubbers and therefore cannot make the material choices or computer predictions that the chemist can. 

Some of the key factors that lead us to select polyurethane foam for upholstery are its durability, resilience, and controllable hardness (or softness, depending on your point of view). Vibration dampening and shock absorbance are important attributes in automobile and public transportation seating. Open cell foams are preferred for these applications because they allow for air and moisture transport, which improve the comfort of passengers who may occupy a seat continuously for several hours. This inherent breathability is also a valuable attribute in mattresses. Shock absorbance plays a key role in selecting flexible polyurethane foams for the packaging of fragile items. 

Applications. The P-O- and P-N-substituted polymers have so far shown the greatest commercial promise. The fluoroelastomers possess good rubber properties with the added advantages of being nonhuming. hydrophobic, and solvent- and luel-resistant. In addition lo these, because of flexibility down to about -fi()"C. these polymers have been used in seals, gaskets, and buses in army tanks, in aviation fuel lines and tanks, as well as in cold-climate oil pipeline applications, These polymers have also round application in various types of shock mounts lor vibration dampening. 

The use of rubber components in vehicles is extensive. Applications include sealing, vibration dampening, and trim. Most rubbers in power train applications are for seals and gaskets (Chapter 8). Chassis applications most often center around vibration dampeners (isolators) for heat exchangers, engine and transmission mounts, and exhaust line isolators. Body and interior applications include interior trim and body sealers. A more thorough list of applications and types of rubbers is presented in Chapter 3. 

The annual volume of used rubber parts that can usefully be removed from the vehicles is estimated at approx. 160,000 ton, of which approx. 50,000 ton come from used vehicles and the rest from other application areas (seals, tubes, profiles, shoe soles, vibration dampeners, drive belts, etc.) [26],... 

Hence, from above properties, the PA/acrylate mbber TPV is particularly suited to various automotive under-the-hood applications where high heat and fluid resistance is needed such as in automotive boots (CVJ, rack, and pinion), noise/ vibration dampening components, dynamic seals, dust covers, underbody/e-coat plugs, grommets, clean air-intake ducts, transmission oil cooler hose, and so on. The nonautomotive applications take advantage of its better overmolding adhesion to nylons to make soft-touch, nylon parts such as power tool handles, overmolded clips, fasteners, and connectors. 

Acrylic polymers have been used as alternatives to nitrile rubbers in some hydraulic and gasket applications because of their excellent heat-resistance properties (236,237). Ethylene-acrylate copolymers have been used as transmission seals, vibration dampeners, dust boots, and steering and suspension seals (238). 

The automotive applications of these materials eover a huge variety of moving parts gears, cams, bearings, ratchets, sliders and valve seats are just a few examples. Beyond reduced maintenance, there are subsidiary benefits in many cases like vibration dampening, power reduction and quietness. 

Formed-in-place gaskets - Silicone RTV sealants are widely used in this application for valve covers, oil pans, thermostats, rear view mirrors. Neoprene sealants have excellent oil and chemical resistance and SBR sealants give good bonding to oily surfaces. Gunnable butyl rubber mastics are used for vibration dampening of panels and as general sealants for frame and body parts. 

Rubber is also used for protection of other materials against fire, heat and wearing. Rubber gives excellent performance as a construction material, in vibration and shock dampening, in elimination of structural noise and is the ultimate material for sealing systems. All basic properties are more or less present in all types of products. For each application individual functional properties are optimized to meet specific requirements. 

There are many applications of porous materials. Their ability to fill space with a minimum weight leads to their use in packaging. Lifejackets and rafts use porous materials because of their low density. Examples of their use as thermal insulators range from Styrofoam cups to heat shields for space craft. Aluminum baseball bats are filled with foam to dampen vibrations. The low elastic moduli and high elastic strains of foams lead to use as cushions and mattresses. Filters are made from porous materials. 

BeryUiuin oxide-filled resins gain high conductivity without loss of electrical properties. Metal particles have heen used as fillers for plastics to improve or impart certain properties. Thus, aluminum has heen used for applications ranging from making a decorative finish to improving thermal conductivity. Copper particles are used in plastics to provide electrical conductivity. Lead is used because it dampens vibrations, acts as barrier to gamma-radiation, and has high density. 

Other applications are automotive body seals, mounts, weather-stripping, roofing, hose, tubing, ducts, and tires. Molded EPDM rubber is used for bumpers and fillers to dampen vibrations around the vehicle. EPDM can be bonded to steels, aluminum, and brass, with modified polyacrylic acid and polyvinylamine water-soluble coupling agents. 

Microballoons have been used for gap filling, where the spheres dampen sound or vibration in the structure. In the medical area, microballoons have been evaluated as a skin replacement for burn victims and phantom tissue for radiation studies. An important application is in nitroglycerin-based explosives, in which microballoons permit a controlled sequential detonation not possible with glass spheres. 

Other substituted polynorbornene copolymers have been developed for encapsulation, cover coating, and microelectronic applications. Elf Atochem is running a small plant for polynorbornene (Norsorex ) produced by ROMP in France. Norsorex is used in the automotive industry for vibration and noise dampening and for soft seals and gaskets. 

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