Butyl rubber additives

Halogenated Butyl Rubber. The halogenation is carried out in hydrocarbon solution using elemental chlorine or bromine in a 1 1 molar ratio with enchained isoprene. The reactions ate fast chlorination is faster. Both chlorinated and brominated butyl mbbers can be produced in the same plant in blocked operation. However, there are some differences in equipment and reaction conditions. A longer reaction time is requited for hromination. Separate faciUties are needed to store and meter individual halogens to the reactor. Additional faciUties are requited because of the complexity of stabilising brominated butyl mbber. 

Butyl Rubber. In butyl mbber, isoprene is enchained by 1,4-addition ia the trans configuration (74). 

In addition there is the possibility that other olefins may generate polymers with low Tg s which show little or no crystallinity at room temperature and are therefore potentially elastomeric. One commercial example is butyl rubber (designated HR), a copolymer of isobutene with a small amount of isoprene. 

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. 

Chlorobutyl rubber is prepared by chlorination of butyl rubber (chlorine content is about 1 wt%). This is a substitution reaction produced at the allylic position, so little carbon-carbon double unsaturation is lost. Therefore, chlorobutyl rubber has enhanced reactivity of the carbon-carbon double bonds and supplies additional reactive sites for cross-linking. Furthermore, enhanced adhesion is obtained to polar substrates and it can be blended with other, more unsaturated elastomers. 

BR is similar to NR in its ability to compound with other materials. Some specific aspects related to additives for butyl rubber are given below. 

Chemical and Other Specialty Manufacture A wide variety of products may be derived from petroleum feed stocks, including such diverse materials as alcohols, butyl rubber, sulfur, additives, and resins. Other specialties such as solvent naphthas, white oils, Isopars, Varsol, may also be produced. As indicated previously the respective chemical affiliate usually has responsibility for products broadly classified as petrochemicals. 

Chemical pretreatments with amines, silanes, or addition of dispersants improve physical disaggregation of CNTs and help in better dispersion of the same in rubber matrices. Natural rubber (NR), ethylene-propylene-diene-methylene rubber, butyl rubber, EVA, etc. have been used as the rubber matrices so far. The resultant nanocomposites exhibit superiority in mechanical, thermal, flame retardancy, and processibility. George et al. [26] studied the effect of functionalized and unfunctionalized MWNT on various properties of high vinyl acetate (50 wt%) containing EVA-MWNT composites. Figure 4.5 displays the TEM image of functionalized nanombe-reinforced EVA nanocomposite. 

Wear full protective clothing consisting of the M3 butyl rubber suit with hood, M2A1 boots, M3 gloves, underwear, M9 series mask and coveralls (if desired). For general lab work, wear gloves and lab coat with M9, Ml7, or M40 mask readily available. In addition, wear daily clean smock, foot covers, and head cover when handhng contaminated lab animals. 

Butyl rubber - This material generally had the least endurance in fatigue tests, but it may be adequate for some cardiovascular applications. Advantages include less sensitivity to stress concentrators than Pellethane, a very low permeability to fluids, a moderate creep resistance and widespread availability at low cost. Disadvantages include a relatively low fatigue resistance compared to the elastomers specifically designed for these applications. The rubber tested was not designed for medical applications and had standard rubber additives and modifiers that were cytotoxic unless the material was extracted after manufacture. 

Chlorinated additive flame retardants, 11 468-470, 471-473t Chlorinated aromatics, 6 242 decomposition using microwaves, 16 555 Chlorinated butyl rubber, 4 436 development of, 4 434 manufacture, 4 400, 442-444 Chlorinated ethanes... 

In addition to the standard laboratory protection, such as safety goggles and chemically resistant butyl rubber gloves, a personal HF gas monitor with audible alarm and a safety sensor for liquids, as described in Section 10.4, are commercially available [2], For detailed information about the toxic effects of HF, see references Fi5, Wa8 and Re4. 

Chlorination of natural rubber (NR) is carried out with chlorine in carbon tetrachloride solution at 60-90°C to yield a chlorinated rubber containing about 65% chlorine, which corresponds to 3.5 chlorine atoms per repeat unit. The process is complex and includes chlorine addition to the double bond, substitution at allylic positions, and cyclization. Chlorinated rubber has high moisture resistance and is resistant to most aqueous reagents (including mineral acids and bases). It is used in chemical- and corrosion-resistant paints, printing inks, and textile coatings. Bromination of butyl rubber is also practiced [Parent et al., 2002]. 

Vinyl-type addition polymerization can also be carried out with acidic catalysis such as boron tnfluoride or tin tetrachloride and with basic catalysis such as alkali melals or alkali alkyls. An example of the first ease is the low-temperature polymerization of isobutene, which gives Vistanex" and butyl rubber an example of the second type is the polymerization of butadiene with sodium, which leads to buna rubber. 

HMX was first evaluated with hydrocarbon binders (Butarez, a carboxy-terminated polybutadiene, and Butyl rubber) because of their high thermal stability, in addition to the expected advantages of high impetus levels and low flame temps. In the Butarez binder, an 85% HMX level produced an impetus of 370000 ft-lbs/lb and a flame temp of 2540°K. At 84% HMX, the system was under-oxidized, at 86% the flame temp exceeded 2600°K. Because of a less favorable heat of formation, higher HMX loadings were required for the Butyl rubber system, ie, about 87% HMX and 13% Butyl rubber vs 85% HMX and 15% Butarez for an impetus of 370000 ft-lbs/lb. In the hydrocarbon formulations, the Butarez polymer appeared more attractive thermodynamically... 

Small Quantities. Wear butyl rubber gloves, laboratory coat, and eye protection. Work in the fume hood. To a 50-mL, three-necked, round-bottom flask equipped with stirrer, thermometer, and dropping funnel, add 1 mL of water, 3 mL of concentrated hydrochloric acid, and 2 g (0.008 mol) of 3,3 -dichlorobenzidine. The temperature is maintained at -5 to OX by a cooling bath, while 0.2 g (0.0084 mol) of 97% sodium nitrite dissolved in 1.4 mL of water is added dropwise to the solution or slurry of dichlorobenzidine hydrochloride. Stirring is continued an additional 30 minutes after addition is complete. While maintaining the temperature at -5 to 0°C, 16.6 mL (0.16... 

Eliminate all sources of ignition. Wear butyl rubber gloves, large and heavy face shield, goggles, and laboratory coat. Cover spill with dry sand. Scoop into a container and transfer to the fume hood. Decompose by cautious addition of dry butanol (40 mol butanol to 1 mol hydride or 26 mL/g hydride) until reaction ceases. Slowly add mixture to a pail of cold water. Let stand for 24 hours. Neutralize with 6 M hydrochloric acid (cautiously add concentrated acid to an equal volume of cold water). Decant the solution to the drain. Treat the solid residue as normal refuse.4 5... 

Wear eye protection, butyl rubber gloves,10 and laboratory coat. Cover spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand.11 Scoop the solid into a container, transport to the fume hood, and slowly add to water allowing 20 mL of water for each 1 g of hydrazine. Remove the clay and sand by filtration. For each 1 g of hydrazine, place 120 mL (about 25% excess) of household laundry bleach (containing 5.25% sodium hypochlorite) into a three-necked, round-bottom flask equipped with a stirrer, thermometer, and dropping funnel. Add the aqueous hydrazine dropwise to the stirred hypochlorite solution at such a rate that the temperature is maintained at 45-50°C. The addition takes about 1 hour. Stirring is continued overnight (at least 12 hours). The reaction mixture can be flushed down the drain with at least 50 times its volume of water.12 13... 

Reaction Mixtures. Wear butyl rubber gloves, laboratory coat, and eye protection. In the fume hood behind a shield, cautiously and slowly carry out the following procedure. Treat the stirred reaction mixture from n grams of lithium aluminum hydride by successive dropwise addition of n mL of H20, n mL of 15% sodium hydroxide solution and 3n mL of H20. This produces a granular precipitate that is removed by filtration and treated as normal refuse. Wash the filtrate into drain.17... 

Small Quantities. Wear eye protection, laboratory coat, and butyl rubber gloves. Work in the fume hood. Add tributylphosphine (10.1 g, 0.05 mol) dropwise while stirring to a 25% excess of hypochlorite (670 mL of laundry bleach or 55 g calcium hypochlorite in 200 mL of water). The temperature of the reaction should be monitored. After addition is complete and the reaction has subsided, filter the solid and package it for disposal by burning. Wash the aqueous solution into the drain.5... 

---