Sulfur rubbery

Sulfur trioxide Rubbery form of SO3 precipitates from solution of SO3 in SOa 0 -U- X Low melting fibrous form melts at 31.5°C... 

Another way of modifying unsaturated PHAs in the bulk is by crosslinking of the material. This has been accomplished by either chemical reaction with sulfur or peroxides [109, 110], or by radiation curing [91, 111]. In all cases, crosslinking altered the ultimate material properties drastically, yielding a true rubbery material. The advantages of applying rubbers from crosslinked PHAs over the use of current rubbers will be elaborated in Sect. 4.5. 

The history of polysulfides began over 150 years ago. In 1838 chemists in Switzedand reported that the reaction of chloraetherin (1,2-dichloroethane) with potassium polysulfide gaveambivalent a rubbery, intractable, high sulfur semisolid. Subsequently there were reports of similar products obtained by various methods, but the first useful products were developed from studies in the late 1920s. This led to the formation of Thiokol Corp. which began production of the ethylene tetrasulfide polymer Thiokol A in 1928, the first synthetic elastomer manufactured commercially in the United States. One of the first successful applications of Thiokol A [14807-96-6] was for seals where its resistance to solvents justified its relatively high price. 

This is broadly in agreement with the findings from copolymerization (Table 22 and Section VI-B). The introduction of comonomer units into PTHF reduces its crystallinity and rubbery materials generally result. In one case allylglycidyl ether was copolymerized so that the pendant olefinic side chains would allow sulfur vulcanization (7). 

Many of the polymers formed from conjugated dienes are elastic and are used to manufacture synthetic rubbers. The raw polymers usually are tacky and of little direct use, except as adhesives and cements. They are transformed into materials with greater elasticity and strength by vulcanization, in which the polymer is heated with sulfur and various other substances called accelerators, with the result that the polymer chains become cross-linked to one another by carbon-sulfur and carbon-carbon bonds. Some of the cross-linking appears to occur by addition to the double bonds, but the amount of sulfur added generally is insufficient to saturate the polymer. With large proportions of sulfur, hard rubberis formed such as is used in storage-battery cases. 

Solid polycatena sulfur comes in many forms as described by their names rubbery S, plastic S, lamina S, fibrous S, polymeric S, and insoluble S which is also termed S, or S. Fibrous S consists of parallel helical chains of sulfur atoms whose axes are arranged on a hexagonal close-packed net 463 pm apart. The structure contains both left- and right-handed helices of radius 95 pm... 

In the dark, the surface attack of CS2 is said to leave a rubbery insoluble fraction similar to polymeric sulfur. 

The straw-colored liquid, Sg, is called A-sulfur, and the dark red liquid consisting of very long chains is called p-sulfur. Wheft this liquid is rapidly cooled by being poured into water it forms a rubbery supercooled liquid, insoluble m carbon... 

TOth only small amounts (< 10%) of 0-pinene units in the chain rubbery co-pol3nnen may be expected. These novel rubbers should be vulcanizable with sulfur... 

Sulfur Vulcanization of Rubbery Poly(isobutylene-co-P-Pinene). .. 35... 

In contrast, the isobutylene-rich rubbery copolymers exhibited useful properties i.e., vulcanizability with sulfur and resistance to ozone, and these products have been further characterized. 

Copolymers containing up to 10 mole% 0-pinene are rubbery (Tg -53°) and can be sulfur vulcanized. The non-filled vulcanizates are very soft rubbers (e.g., 300% modulus 7.7 kg/cm or 110 psi) with high ultimate tensile strength (eg, tensile strength 246 kg/cm or 3,500 psi). The high tensile strength is attributed to stress induced crystallization. 

This assumption is incorrect. Already the earliest patent literature on desulfurization of coal gasification, "city gas", and coal combustion gas desulfurization ( 2) contains persistant and recurring reports of decomposition of sulfur scrubbing liquids, yielding unexpected and difficult-to-handle products, among them nascent, polymeric elemental sulfur which forms rubbery and sticky films causing breakdown of equipment. Our... 

Solid poly catena sulfur comes in many forms it is present in rubbery S, plastic (x)S, lamina S, fibrous (Vr>commercial product Crystex. All these are metastable mixtures of allotropes containing more or less... 

When pure, the product has a very powerful sulfurous odor, but at high dilution it develops a pleasant, grilled, smoky and very characteristic note (Ohloff and Flament, 1979). At a concentration of 1 ppm, it has a rubbery, burnt, sulfury, seafood flavor (Chemisis, 1995). The odor threshold in water is 5ppb (Tressl and Silwar, 1981), perceived as cooked meat with slight coffee note from 10 100 ppb. Tressl (1989) reported a threshold of 0.5ppb with a roast sulfur note at 10-50ppb. 

As discussed in the previous section, this laboratory has not been able to apply the technique of differential scanning calorimetry to a study of the crystallization of sulfur cooled from the melt above 159 °C. Tobolsky (20) has shown that the so-called plastic sulfur, obtained by quick-quenching the sulfur melt from above 159 °C, is in a rubbery state... 

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