Diene rubbers polybutadiene

Ethylene-propylene-diene rubber Polybutadiene W. Germany 2,326,198 1973 Revertex Ltd. 

The large amounts of NR and SBR consumed by the world economy is due to the fact that they are the main tyre rubbers , with the tread compounds of tyres (particularly those of passenger vehicles and trucks) usually being sulfur-cured compounds based on these two diene-type rubbers, sometimes with an amount of another diene rubber (polybutadiene) added to improve properties such as flex crack resistance. 

DMA has been found to be particularly useful in studying blends of rubbers, particularly those that are structurally similar, and so are difficult to characterise by the use of other techniques such as infi ared spectroscopy. A good example of this is the diene rubbers (polybutadiene, polyisoprene, styrene-butadiene rubber, etc.), which are often blended together to produce a wide range of commonly encountered products, e.g. car and truck tyres, seals and gaskets. The difference in the glass transition temperatures of these rubbers (see Table 6.10 below) is sufficient for them to be resolved from each other in a DMA experiment (see Figures 6.9 and 6.10). 

As of this date, there is no lithium or alkyl-lithium catalyzed polyisoprene manufactured by the leading synthetic rubber producers- in the industrial nations. However, there are several rubber producers who manufacture alkyl-lithium catalyzed synthetic polybutadiene and commercialize it under trade names like "Diene Rubber"(Firestone) "Soleprene"(Phillips Petroleum), "Tufdene"(Ashai KASA Japan). In the early stage of development of alkyl-lithium catalyzed poly-butadiene it was felt that a narrow molecular distribution was needed to give it the excellent wear properties of polybutadiene. However, it was found later that its narrow molecular distribution, coupled with the purity of the rubber, made it the choice rubber to be used in the reinforcement of plastics, such as high impact polystyrene. Till the present time, polybutadiene made by alkyl-lithium catalyst is, for many chemical and technological reasons, still the undisputed rubber in the reinforced plastics applications industries. 

Elastomers, synthetic -acrylic elastomers [ELASTOMERS, SYNTHETIC - ACRYLIC ELASTOMERS] (Vol 8) -butyl rubber [ELASTOMERS, SYNTHETIC - BUTYL RUBBER] (Vol 8) -chlorosulfonated polyethylene [ELASTOMERS, SYNTHETIC - CHLOROSULFONATED POLYETHYLENE] (Vol 8) -ethylene-acrylic elastomers [ELASTOMERS, SYNTHETIC - ETHYLENE-ACRYLIC ELASTOMERS] (Vol 8) -ethylene-propylene-diene rubber [ELASTOMERS,SYNTHETTC - ETHYLENE-PROPYLENE-DIENE RUBBER] (Vol 8) -fluorocarbon elastomers [ELASTOMERS, SYNTHETIC - FLUOROCARBON ELASTOMERS] (Vol 8) -nitrile rubber [ELASTOMERS, SYNTHETIC - NITRILE RUBBER] (Vol 8) -phosphazenes [ELASTOMERS, SYNTHETIC - PHOSPHAZENES] (Vol 8) -polybutadiene [ELASTOMERS, SYNTHETIC - POLYBUTADIENE] (Vol 8) -polychloroprene [ELASTOMERS, SYNTHETIC - POLYCHLOROPRENE] (Vol 8) -polyethers (ELASTOMERS, SYNTHETIC - POLYETHERS] (Vol 8) -polyisoprene [ELASTOMERSSYNTHETTC - POLYISOPRENE] (Vol 9) -survey [ELASTOMERS, SYNTHETIC - SURVEY] (Vol 8)... 

RESINS (Acrylonitrile-Butadiene-Styrene). Commonly referred to as ABS resins, these materials are thermoplastic resins which are produced by grafting styrene and acrylonitrile onto a diene-rubber backbone. The usually preferred substrate is polybutadiene because of its low glass-transition temperature (approximately —80°C). Where ABS resin is prepared by suspension or mass polymerization methods, stereospedfic diene rubber made by solution polymerization is the preferred diene. Otherwise, the diene used is a high-gel or cross-linked latex made by a hot emulsion process. 

However, no method of polymerisation known before 1954 allowed one to obtain polymers with a high regularity of structure from the most common conjugated dienes. A true breakthrough in the development of conjugated diene rubbers took place after the discovery of stereospecific polymerisation with transition metal-based coordination catalysts. From the late 1950s, a rapid development of industrial production of solution types of polybutadiene by means of polymerisation with Ziegler-Natta catalysts was observed. 

Wettability of Elastomers and Copolymers. The wettability of elastomers (37, 38) in terms of critical surface tension was reported previously. The elastomers commonly used for the reinforcement of brittle polymers are polybutadiene, styrene-butadiene random and block copolymers, and butadiene-acrylonitrile rubber. Critical surface tensions for several typical elastomers are 31 dyne/cm. for "Diene rubber, 33 dyne/cm. for both GR-S1006 rubber and styrene-butadiene block copolymer (25 75) and 37 dyne/cm. for butadiene-acrylonitrile rubber, ( Paracril BJLT nitrile rubber). The copolymerization of butadiene with a relatively polar monomer—e.g., styrene or acrylonitrile—generally results in an increase in critical surface tension. The increase in polarity is also reflected in the increase in the solubility parameter (34,39, 40) and in the increase of glass temperature (40). We also noted a similar increase in critical surface tensions of styrene-acrylonitrile copolymers with the... 

Polymer of hi molecular weight are in the main inccmq>atible, but it is often advantageous to compound two polymers in order to obtain a combination of new physical properties which either polymer alone cannot have. For example, EPDM rubber is inconq>atible with diene rubbers such as polyisrprene, polybutadiene,... 

Diene . [Firestone Syn. Rubber) Polybutadiene robber, used to produce tires, retreads, molded and extruded goods impact mo er for ABS andPS. 

Polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polystyrene (PS), polymethylmethacrylate (PMMA) Ethylene-tetratluoro-ethylene (ETFE), tetrafluoroethylene/ hexafluoropropylene (THV), polyethylene (PE), polypropylene (PP) Epoxy resin (EP), polyester resin (UP), phenol resin (PF), resorcin resin (RF), polyurethane (PUR) Styrene-butadiene-rubber (SBR), polybutadiene-rubber (BR), ethylene-propylene-diene-rubber (EPDM)... 

Thiols add to diene rubbers by a free-radical mechanism. Thus antioxidants, like 4-(mercapto-acetamido)-diphenylamine, add -SH groups to the double bonds of cis-polyisoprene and polybutadiene in the presence of free>radical initiators. " ... 

It is proposed that this is due to attack of carbonyl oxides, in their biradical form, on the rubber double bonds. Typical diene rubbers (polyisoprene and polybutadiene) have rate constants several orders of magnitude greater than polymers having a saturated backbone (polyolefins). Other unsaturated elastomers having high reaction rates with ozone include styrene-butadiene (SBR) and acrylonitrile-butadiene (NBR) rubbers. As an example, Polychloroprene (CR) is less reactive than other diene rubbers, and it is therefore inherently more resistant to attack by ozone. 

Properties Ethylene propylene diene Nitrile rubber Poly- chloroprene Natural rubber Poly- isoprene Styrene butadiene rubber Butyl rubber Polybutadiene... 

In principle the hydrogenation of a diene rubber is one of the simplest reactions. Complete hydrogenation of polybutadiene would give a polyethylene structure whilst hydrogenation of polyisoprene that of an alternating ethylene-propylene copolymer. 

Like the very important diene rubbers (polyisoprene, polybutadiene and SBR) the ethylene-propylene rubbers are hydrocarbons. They are therefore resistant to polar solvents but dissolve (when unvulcanized) or swell (when vulcanized) in hydrocarbons. Being saturated they are somewhat inert chemically and therefore have good resistance to oxygen, ozone, acids and alkalies. Besides being attacked by peroxide radicals they may also be halogenated. 

The general reaction chemistry used in the synthesis of common rubbers and elastomers mentioned in Table 21.1 is described in the following. The discussion covers four types of rubbers styrene-butadiene rubbers (SBRs), polybutadiene, ethylene-propylene-diene rubbers, and thermoplastic polyurethanes. 

Approaches to the prediction of the long-term ageing behaviour of vulcanised diene rubbers are discussed, and studies of the photooxidative and ozone degradation of polybutadiene, polyisoprene, SBR and nitrile rubber under accelerated artificial ageing conditions are reported. 12 refs. 

MAJOR POLYMER APPLICATIONS ABS, acrylics, cellulose acetate, cellulose acetate butyrate, ethylene propylene diene copolymer, polybutadiene, polyimide, rubber, styrene acrylate copolymer ... 

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