Chlorosulfonation of polyethylene

Chlorosulfonated Polyethylene. This elastomer is made by the simultaneous chlorination and chlorosulfonation of polyethylene in an inert solvent. The resulting polymer is an odorless, colorless chip that is mixed and processed on conventional mbber equipment. The polymer typically contains 20-40% chlorine and 1% sulfur groups (see ElASTOL RS, SYNTHETIC-Cm OROSULFONATEDPOLYETHYLENE) (8). 

Elastomeric polymers can be produced by the chlorination or chlorosulfonation of polyethylene. Both products start with polyethylene, either in solution or in aqueous suspension, which then is reacted to give the specified... 

How is chlorosulfonation of polyethylene carried out industrially Explain and write the chemical equations for the reactions. How is the product used ... 

The initial development was the creation of chlorinated polyethylene, however it was difficult to vulcanize with the limited peroxides available at the time. The process was altered to permit simultaneous chlorination and chlorosulfonation of polyethylene which allowed the elastomer to be cured with sulfur-bearing curatives. In 1951, Du Pont commercialized Hypalon S-1, a chlorinated polyethylene, and Hypalon S-2, a chlorosulfonated polyethylene, later renamed Hypalon 20. S-1 was quickly withdrawn from the market due to the much improved Hypalon 20, which is stiU available today. 

Linear polyethylene (high density) was introduced in the late 1950s, with the development of coordination catalysts. Chlorosulfonation of these base resins gave products that were superior to the eadier, low density types in both chemical resistance and mechanical properties and with distinct advantages in mbber processibiUty (6,7). 

Chlorosulfonated polyethylene A product obtained by treatment of polyethylene by chlorine and sulfur dioxide. It is an elastomer highly resistant to chemicals and ozone. 

Examples are the sulfonating of polyethylene film with chloro-sulfonic acid (60) the sulfonating of sheets of phenolformaldehyde resin (77) the treatment of a film consisting of polystyrene and polyvinylchloride with concentrated sulfuric acid (4) the sulfonating of films consisting of aliphatic vinylpolymers with chlorosulfonic acid (125) the sulfonating of copolymers of a monovinyl- and a polyvinyl compound (30). Also are used copolymers of aromatic monovinyl-compounds and linear aliphatic polyene hydrocarbons (3) copolymers of an unsaturated aromatic compound and an unsaturated aliphatic compound (76), and of reaction products of poly olefines and partially polymerized styrene (173). 

Low chlorination of polyethylene, causing random substitution, reduces chain order and thereby also the crystallinity. The low chlorine products (22-26% chlorine) of polyethylene are softer, more rubber-like, and more compatible and soluble than the original polyethylene. However, much of the market of such materials has been taken up by chlorosulfonated polyethylene (Hypalon, Du Pont), produced by chlorination of polyethylene in the presence of sulfur dioxide, which introduces chlorosulfonyl groups in the chain. 

Definition Prod, of chlorosulfonation of a carbon tetrachloride solution of polyethylene with chlorine and sulfuryl chloride elastomer used in vulcanized and unvulcanized form vulcanizates have exc. oil/chemi ozone/weather resist. 

Chlorosulfonation or polyethylene is a commercial process. The reaction resembles chlorination in the step of hydrogen abstraction by chlorine radicals. It is catalyzed by pyridine and can be pictur as follows... 

Chlorosulfonated polyethylene is a saturated chlorohydrocarbon rubber produced from CI2, SO2, and a number of polyethylenes, and contains about 20 to 40% chlorine and 1 to 2% sulftir as sulfonyl chloride. Sulfonyl chloride groups are the curing or cross-linking sites.2 CSM properties are largely based on initial polyethylene (PE) and percent chlorine. A free-radical-based PE with 28% chlorine and 1.24% S has a dynamic shear modulus range from 1000 to 300,000 Ib/in (7 MPa to 2.1 GPa). StiflEhess differs for free-radical-based PE and linear PE, with chlorine content at about 30%, CI2 free-radical-based PE stiffness decreases to minimum value, and at about 35%, CI2 content linear PE stiffness decreases to minimum value. When the CI2 content is increased more than 30 and 35%, respectively, the stiffness (modulus) increases.23... 

Further modification of polyethylene is possible by chemical substitution of hydrogen atoms this occurs preferentially at the tertiary carbons of a branching point and primarily involves chlorination, sulfonation, phosphorylination, and intermediate combinations. (See chlorinated polyethylene chlorosulfonated polyethylene phosphorylated polyethylene ionomer.)... 

Fig. 4.15 TEM micrograph of a chlorosulfonic acid stained linear polyethylene crystallized isothermally from the melt reveals the electron dense interlamellar surfaces typical of polyethylene.

Peterlin et al. [157] described the use of iodine vapor, at 60°C (24 h) to reveal the structure in PE fibrils drawn from solution grown single crystals. Andrews et al. [78] extended this method to prestaining a block of material prior to ultrathin sectioning. They showed the contrast enhancement of PE spherulites by action of the iodine. However, the iodine dissipates upon standing in air and is known to vaporize in the vacuum of the electron microscope. The chlorosulfonic acid method (Section 4.4.4) has replaced iodine staining of polyethylene. 

An important staining technique was developed by Kanig [114] for the enhanced contrast of polyethylene, a material which has been a model compound for fundamental polymer studies. PE crystals cannot be sectioned, nor are they stable in the electron beam, due to radiation damage. The chlorosulfonation procedure crosslinks. 

Chlorosulfonated polyethylene is a saturated chlorohydrocarbon rubber produced from CI2, SO2, and a number of polyethylenes, and contains about 20 to 40 percent chlorine and 1 to 2 percent sulfur as sulfonyl chloride. Sulfonyl chloride groups are the curing or... 

Chlorosulfonated Polyethylenes. Chlorosulfonated polyethyl-enes are made from the reaction of polyethylene chains with various chlorine and sulfonyl chloride groups. The degree of substitution and the ratio of the types of groups depend on the reaction conditions. They can be represented as follows ... 

Treatment of polyethylene with chlorosulfonic acid before the application of adhesive enhanced the adhesion of the polymer to itself and to aluminium and natural sponge rubber. ... 

The sulfonation of polyethylene membranes was examined under various experimental conditions and the results showed that sulfonation greatly enhanced the water permeability of the resultant membranes. A lower concentration of chlorosulfonic acid at low temperature was preferable, so that only the surface and inner walls of the polymer were sulfonated and the mechanical properties of the membrane were not damaged. The electromicroscopy of polythene is facilitated by staining the polymer by immersing pieces of the polymer in chlorosulfonic acid at 60 °C for several hours. Chlorosulfonated polyethylene rubbers are useful for specific purposes, e.g. as ozone-resistant hoses. ... 

Membranes composed of a sulfonated interpolymer of polyethylene and sjdrene-DVB copolymer were prepared by reaction with mixtures of chlorosulfonic acid and dichloroethane of different compositions. It was discovered that the electrical properties of the resultant membranes were related to the degree of sulfonation. See also VK. Shahi, S.K. Thampy and R. Rangarajan React. Funct. Polym., 2000, 46(1), 39 Chem. Abs., 134, 163756 (Chapter 8, Section 6). 

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