Vulcanizate tensile weight

Among the main molecular structural variables in EPDMs that are stipulated by catalyst systems and that affect the vulcanizate tensile properties we may mention molecular weight (MW) and MWD, degree of unsaturation (LG=C 1) and its distribution in the polymer, composition (C S) and monomer sequence length distribution along molecular chains, and long-chain branching if present. Effect of... 

Increase in the molecular weight of the polychloroprene, increasing viscosity and tensile strength of vulcanizates. 

A VDF unit also follows FIFP m the structurally much more complex terpo-lymers [30] Dipolymers contain 60 wt % VDF (66% F) and terpolymers contain 33-50 wt % VDF (66-69 5% F) and generally less than 28 wt % TFE Molecular weights range from 1 5 x 10 to 10 Their respective continuous service temperature ranges are -18 to 210 °C and -12 to 230 °C Dipolymer vulcanizates retam over 50% of their tensile strength for more than 1 year at 200 °C or for 2 months at 260 C... 

Butyl ruhher vulcanizates have tensile strengths up to 2,000 psi, and are characterized hy low permeahility to air and a high resistance to many chemicals and to oxidation. These properties make it a suitable rubber for the production of tire inner tubes and inner liners of tubeless tires. The major use of butyl rubber is for inner tubes. Other uses include wire and cable insulation, steam hoses, mechanical goods, and adhesives. Chlorinated butyl is a low molecular weight polymer used as an adhesive and a sealant. 

Fillers in Rubber. Carbon black and calcium silicate are able to reinforce rubber. For example, the tensile strength of an SBR vulcanizate can be raised from 350 to 3500 Ib/in. by compounding with 50% of its weight of carbon black (54). The activity of the carbon black depends on particle size and shape, porosity, and number of active sites, which are less than 5% of the total surface. Elastomers of a polar nature, such as chloroprene or nitrile rubber, will interact more strongly with filler surfaces having dipoles, such as -OH and -CCX)H groups or chlorine atoms. 

Figure 10.25. Tensile strength data for Kraton 101 (SBS triblock polymer) ( ) compared with those for an SBR vulcanizate containing 25% by volume of 350-A polystyrene latex spheres (O) (Morton and Healy, 1968) and SBR vulcanizate reinforced with 30% by weight HAF carbon black filler ( ). (Morton and Healy, 1968 Smith, 1970.)...

Addition of fillers can dramatically change mechanical properties of elastomer materials. For example, a pure gum vulcanizate of general purpose styrene-butadiene rubber (SBR) has a tensile strength of no more then 2.2 MPa but, by mixing in 50 parts per hundred weight parts of rubber (p.p.h.r) of a active CB, this value rises more than 10 times to 25 MPa. How CB, being fine powder of practically no mechanical strength, can make reinforcement in rubbers, similar to... 

Wootthikanokkhan and Tongrubbai examined the tensile properties of NR/ACM vulcanizates. It was found that increasing the NR content in the recipe improved the mechanical properties. However, that was not the case when the same specimens were heated for 24 h at 140 °C. After this thermal treatment, the vulcanizates with increased ACM weight ratio maintained to a greater extent their initial strain percentage compared to these with lower ACM content. To improve the mechanical response of NR/ACM sulfur-cured vulcanizates, incorporation of CB or compatibilization with poly(isoprene-butyl acrylate) block copolymer (at 5 wt%) has been proposed. ... 

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