Specialty rubbers

Nando, G.B. Reactive Miscible Blends from Ethylene Copolymers and Specialty Rubbers, 156th Meeting of the Rubber Division, American Chemical Society, Orlando EL, September 1999, Paper No. 55. 

E I du Pont Nemours Co Elastomer Chemicals Dept, Wilmington Delaware, USA, R M Murray and D C Thompson, The Neoprenes, Formal Reports-Basic Principles of Compounding, Informal reports-Basic Details of Compounding and Test data, Hypalon Reports, Viton Bulletins, Adiprene Bulletins and Extensive reports on various Specialty Rubbers. 

Specialty rubbers -acrylic elastomers [ELASTOMERS, SYNTHETIC - ACRYLIC ELASTOMERS] (Vol 8)... 

The serious development of synthetic rubbers commenced in the late 1930s and early 194(ls. accelerated by a cutoff of supplies of natural rubber because of political turmoil and war. Synlhetic rubbers fall into two major classifications (1) general-purpose rubbers, the major volume of which is nevertheless used for tire production and (2) specialty rubbers that essentially find little use in (ires, hut that are important for a number of other categories. Synthetic rubbers have not replaced natural rubber for numerous uses. For large, heavy-duty truck and bus tires, natural rubber tends to mn considerably cooler and wears better than a blend of natural and synthetic rubbers. On the other hand, a tire (read made of a blend of styrene-butadiene (SBR) and butadiene rubber (polybutadiene) wears longer than natural rubber in conventional automobile, usage, where lower temperatures can be maintained. 

Ethylene-propylene rubber (EPR or EPDM) is, basically, a copolymer of ethylene and propylene. Because of the random arrangement of the monomers in the chain, crystallization does not occur, and the material behaves as a rubber. Just as with polyisobutylene, vulcanization with sulphur is impossible (the chain is saturated). Also here, a small amount of another monomer is incorporated, which enables the vulcanization and thus the use as a technical elastomer. EPR has a high resistance against ageing and chemical attack, and is, compared with other specialty rubbers, relatively cheap. 

Hydrogenation is an important method of chemical modification of elastomers. Because of the absence of carbon-carbon unsaturation, hydrogenated elastomers have good resistance to oxidative and thermal degradation, improved weatherability and good resistance towards chemicals and fluids [5-7]. Nitrile rubber (NBR) is a specialty rubber, and because of its oil resistance properties, it has been used in oil-wells and the automotive industry. Hydrogenation of NBR has been studied extensively because of its technological importance [16-19]. 

Chloroprene rubber (Neoprene—trade name of DuPont) was one of the earliest synthetic rubbers, first commercialized in 1932. It has a wide range of useful properties but has not become a true general purpose synthetic rubber, probably because of its cost. It does possess properties superior to those of a number of general purpose polymers, such as oil, ozone, and heat resistance but for these properties other specialized polymers excel. Polychloroprene thus is positioned between the general purpose elastomers and the specialty rubbers. 

Use Antioxidant for polypropylene, high-density polyethylene, spandex fibers, polyamides and specialty rubbers. 

Polyurethane rubbers are a special type of PU elastomer. The PU rubbers are highly resistant to oil and fuel and have high abrasion resistance and tensile strength similar to PU elastomers. Polyurethane rubbers maintain their flexibility even at a temperature as low as -40° C and are thermally stable up to 125°C. Polyurethane rubbers have better mechanical strength and resist abrasion, ozone, and oil better than other specialty rubbers such as acrylates and nitrile butadiene. ... 

Priplast [Unichema Unichema France SA] Azelates or epoxizied oleate plasticizers for PVC, PVDC, PVAc, cellu-losics, specialty rubbers, nitroceOulose, polyvinylbutyral films polyester polyols for polyurethane foam, coatings, and thermoplastic elastomers. 

Global natural rubber consumption is split among tires (75%), automotive mechanical products (5%), nonautomotive mechanical products (10%), and miscellaneous applications such as medical and health-related products (10%). Since the 1960s, the quality and consistency of natural rubber has improved, primarily because of the implementation of standard specifications defining a range of grades of rubber. Natural rubber is available in three basic types technically specified rubbers, visually inspected rubbers, and specialty rubbers. 

While the third monomer can be a conunon diene, like isoprene, more often it is a bridged ring structure with at least one double bond in the ring. In typical terpolymer rubbers with 60 to 40 ratios of ethylene to propylene, the diene components usually comprise about 3% of the total. Some specialty rubbers, however, may contain 10% of the diene or even more. Reaction conditions are always chosen to obtain 1,2 placement of the diene. Dienes in common use are ethylidine norbomene, methylene norbomene, 1,4-hexadiene, dicyclopentadiene, and cycloocadiene ... 

Precaution Combustible Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and irritating fumes Uses Antioxidant/stabilizerfor PP, HOPE, POM, spandex fibers, polyamides, polyesters, PVC, cellulosics, specialty rubbers, food-grade polymers... 

Barium dinonyinaphthalene sulfonate stabilizer, specialty rubber... 

Polymers can exist as liquids, as elastomers or as solids but can be transferred into the gaseous state only tmder very special conditions as are realized in, for example, MALDI mass spectrometry. This is because their molecular weight is so high that thermal degradation sets in before they start to evaporate. Only a few polymers are technically applied in the liquid state (silicon oils, specialty rubbers) but most polymers are applied either as elastomers, or as rigid amorphous or semicrystalline solids. 

The product, poly[l,3-cyclopentylenevinylene], is a commercial synthetic specialty rubber, with a trade name of Norsorex. Reports in the literature show that there may be more than one mechanism of termination [160, 165]. One may be by formation of cyclopropane rings. This is a typical reaction of carbenes [160]. Another one, by a reduction of the transition metal and formation of free radicals [160] ... 

In our early marketing experience with HYTREL, we first positioned it as a competitive replacement for medium to high performance specialty rubbers. Then, as now, rubber products were positioned on the basis of selected properties to fit particular applications. As a result, HYTREL was defin primarily as a rubber, albeit one with thermoplastic processing characteristics, and it was marketed on the basis of its elastomeric properties and heat and chemical resistance. 

Environmental conditions likely to be encountered by aircraft in cortring years can be expected to become more severe, coinciding with advances in aerospace technology. Specialty synthetic rubbers will be needed for the aircraft industry s future sealing requirements. Although rubber compounding techniques on these specialty rubbers, as well as conventional nitriles and neoprenes, have been adopted by seal manufacturers, much research is still needed from leading rubber and chemicals manufacturers R D laboratories and institutions. 

Specialty Rubbers Low gas permeability Butyl Fluorocarbons Viton-Du Pont Seals, O-rings, not in contact with oil Seals, O-rings, in contact with oil and solvents -65 to 250 -20 to 400 Best for gas retention, medium physical properties, medium cost See above... 

The last four decades have seen the introduction of many new rubber to metal adhesives designed to cover the ever increasing range of synthetic rubbers currently available for use in dynamic applications. These include one coat adhesives, adhesives for postvulcanisation bonding, specialty rubber adhesives for silicones, fluorosilicones, fluororubbers, acrylics, and hydrogenated nitrile rubbers, along with the recent introductions of water-based adhesives. 

When Hercules entered the specialty rubber business in 1968 with its two HERCIX)R epichlorohydrin elastomers (Table I), very little was known about their structure. As indicated previously, it should be possible to change the microstructure by altering the catalyst system and in this way optimize the balance of properties. 

If not available, a user could revert back to high-performance vulcanizable specialty rubber compounds, which might increase the cost of production or hurt product performance. 

Butadiene is used to make oil-resistant NBR elastomer, which is fluxed with polyvinyl chloride resin during mixing to prepare an NBR/PVC masterbatch that can be vulcanized with sulfur. Butadiene is used to produce the specialty rubber HNBR. 

---