Butyl rubbers characteristics

Vulcanisation can be effected by diamines, polyamines and lead compounds such as lead oxides and basic lead phosphite. The homopolymer vulcanisate is similar to butyl rubber in such characteristics as low air permeability, low resilience, excellent ozone resistance, good heat resistance and good weathering resistance. In addition the polyepichlorohydrins have good flame resistance. The copolymers have more resilience and lower brittle points but air impermeability and oil resistance are not so good. The inclusion of allyl glycidyl ether in the polymerisation recipe produces a sulphur-curable elastomer primarily of interest because of its better resistance to sour gas than conventional epichlorhydrin rubbers. 

Polyisobutylene has a similar chemical backbone to butyl rubber, but does not contain double carbon-carbon bonds (only terminal unsaturation). Many of its characteristics are similar to butyl rubber (ageing and chemical resistance, low water absorption, low permeability). The polymers of the isobutylene family have very little tendency to crystallize. Their strength is reached by cross-linking instead of crystallization. The amorphous structure of these polymers is responsible for their flexibility, permanent tack and resistance to shock. Because the glass transition temperature is low (about —60°C), flexibility is maintained even at temperatures well below ambient temperature. 

Vulcanised butyl rubber is very similar to vulcanised natural rubber in various physical characteristics but has better resistance to oxidation and has low permeability to gases. Hence, it is widely used in tubes for cycles, scooters, motor cars, etc. It is also used as rubber in many other applications. 

DPE suits, and butyl rubber (NRC, 2001b). The levels were 0.0002 to 0.0008 ng/m3, three orders of magnitude below the EPA criterion of 0.2 ng/m3 for dioxin emissions from incinerators. In the test with neat GB, the product gas contained 0.01 to 0.06 percent phosphine. As noted previously in the section on methods development testing, phosphine can interfere with the measurement of GB. Based on results from the EPA s toxicity characteristic leachate procedure, stabilization would be necessary only for solid wastes derived from DPE suit material, because the cadmium and lead criteria were not met by the treated dunnage in some tests (NRC, 2001b). 

It appears from the evolution of the adhesion index that a distinction has to be made between the interactions carbon blacks are able to have with unsaturated or with saturated (or near-to-saturated) elastomers. Thus, the adhesion index of butyl rubber is enhanced upon oxidation of the black, while the reverse is observed with polybutadiene 38). The improvement of the reinforcing ability of carbon black upon oxidation, in the former case, has been interpreted by Gessler 401 as due to chemical interactions of butyl rubber with active functional groups on the solid surface. Gessler, relating the reinforcing characteristics of the oxidized carbon black for butyl rubber to the presence of carboxyl groups on the surface of the filler, postulated a cationic... 

This depends on the cross link density. With a tighter cure, permanent sets are low. Some high saturation polymers such as butyl rubbers have characteristically high permanent set. 

Butyl Rubber. A synthetic rubber produced by copolymerization of isobutene(98%) with a small proportion(ca 2%) of isoprene or butadiene. Polymerization is conducted at-50 to 100° in a liquid hydrocarbon, with A1C13 as catalyst. Its outstanding property compared with other rubbers is impermeability to gases. The uncured rubber is tacky, but it may be compounded like natural rubber and vulcanized. Butyl rubber has good resistance to chemical attack and to aging even at high temps. It has superior vibration insulation characteristics and abrasion resistance, but relatively low tensile strength and poor flame resistance... 

The most important characteristics of butyl rubber are its low permeability to air and its thermal stability. These properties account for its major uses in inner tubes, tire inner liners, and tire curing bladders. Because of the poor compatibility of butyl with other rubbers (with respect to both solubility and cure), the halobutyls are preferred. The brominated p-methylstyrene-containing butyl rubbers are used in a number of grafting reactions for tire applications and adhesives. Other uses for butyl rubber are automotive mechanical parts (due to the high damping characteristics of butyl), mastics, and sealants.55... 

Grades of butyl differ by the level of unsaturation, molar masses characterized by Mooney viscosity ML 1 + 8 (100 or 125° C), and the characteristics of the eventually added stabilizer (staining or nonstaining). Butyl rubber, which ranks third in total synthetic elastomers consumed, has unique properties and applications, due to its low gas permeability, to its high hysteresis, and to its low level of unsaturation, sufficient for vulcanization but still providing excellent resistance to oxygen and ozone. 

Liquid polymers are useful as tackifiers for rubbers, 72) and acrylic coatings. The most interesting are hydroxytelechelic polybutadienes, especially liquid butadiene-acrylonitrile (85/15) copolymers (trademark CN-15, ARCO). This product, known since 1971 as a tackifier, has the following characteristics viscosity 493 poises at 30 °C, tv[n = 4400, hydroxyl number/chain = 2.5. The incorporation of 5% of CN-15 in ethylene-propylene rubber (EPT Nordel 1070) increases its tack considerably 173) close to that of natural rubber or butyl rubbers (Table 4.1). 

The most common rubber polymers used in SVI closures are natural and butyl rubber (Table 9). Silicone and neoprene also are used but less frequently in sterile products. Butyl rubber has great advantages over natural rubber in that butyl rubber requires fewer additives, has low water vapor permeation properties, and has good characteristics with respect to gaseous (e.g., oxygen) permeation and reactivity with the active ingredient. 

Typical spectral peaks to aid in the identification of coating elastomers and rubbers are shown in Tables 7.4 and 7.5 (Verleye et al., 2001). The tables show that the infrared spectroscopic technique is invaluable in detecting characteristic peaks to identify the differences between chemically similar hydrocarbon polymers, such as polyolefins, natural and butyl rubbers. It is also sensitive enough to show the difference between polyester and polyether urethanes. Modem FUR machines can store, retrieve and compare spectra to enable manufacturers to check quality, identity and characteristics of the polymer materials they use (RAPRA, 2004). 

Butyl rubber like Hypalon, Neoprene or nitrile rubber is a speciality polymer which can be compounded for a soft, deformable elastic vulcanisate similar to the other elastomers, but having certain distinctive characteristics, like low permeability to all gases and resistance to ageing and ozone cracking. Butyl has poor oil resistance and medium low temperature flexibility. 

Blends of polyolefins (e.g., HPDE/LDPE, LDPE/ ethylene copolymers, PP/EPDM, PP/HDPE/EPDM, HDPE/butyl rubber) have been commercial since the late 1960 s and early 1970 s. Specific film formulations were commonly based on polyolefin blends to achieve the proper balance of processing, environmental stress crack resistance, modulus, toughness, cling, transparency, filler acceptance, printability, tear resistance, shrinkage characteristics, and permeability. Ethylene-propylene mbber (EPR, EPDM) was commonly incorporated into polypropylene as an impact modifier at moderate levels and as a flexibilizer at high levels. One of... 

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