Chlorosulfonate polyethylene

Acryhc stmctural adhesives have been modified by elastomers in order to obtain a phase-separated, toughened system. A significant contribution in this technology has been made in which acryhc adhesives were modified by the addition of chlorosulfonated polyethylene to obtain a phase-separated stmctural adhesive (11). Such adhesives also contain methyl methacrylate, glacial methacrylic acid, and cross-linkers such as ethylene glycol dimethacrylate [97-90-5]. The polymerization initiation system, which includes cumene hydroperoxide, N,1S7-dimethyl- -toluidine, and saccharin, can be apphed to the adherend surface as a primer, or it can be formulated as the second part of a two-part adhesive. Modification of cyanoacrylates using elastomers has also been attempted copolymers of acrylonitrile, butadiene, and styrene ethylene copolymers with methylacrylate or copolymers of methacrylates with butadiene and styrene have been used. However, because of the extreme reactivity of the monomer, modification of cyanoacrylate adhesives is very difficult and material purity is essential in order to be able to modify the cyanoacrylate without causing premature reaction. 

Many cellular plastics that have not reached significant commercial use have been introduced or their manufacture described in Hterature. Examples of such polymers are chlorinated or chlorosulfonated polyethylene, a copolymer of vinyUdene fluoride and hexafluoropropylene, polyamides (4), polytetrafluoroethylene (5), styrene—acrylonitrile copolymers (6,7), polyimides (8), and ethylene—propylene copolymers (9). 

Most elastomers can be made iato either opea-ceUed or closed-ceUed materials. Natural mbber, SBR, nitrile mbber, polychloroprene, chlorosulfonated polyethylene, ethylene—propylene terpolymers, butyl mbbers, and polyacrylates have been successfuUy used (4,111,112). 

The use of TAG as a curing agent continues to grow for polyolefins and olefin copolymer plastics and mbbers. Examples include polyethylene (109), chlorosulfonated polyethylene (110), polypropylene (111), ethylene—vinyl acetate (112), ethylene—propylene copolymer (113), acrylonitrile copolymers (114), and methylstyrene polymers (115). In ethylene—propylene copolymer mbber compositions. TAG has been used for injection molding of fenders (116). Unsaturated elastomers, such as EPDM, cross link with TAG by hydrogen abstraction and addition to double bonds in the presence of peroxyketal catalysts (117) (see Elastol rs, synthetic). 

At this point in the process, thermoplastic and chlorosulfonated polyethylene (CSPE) membranes are complete and are ready for packaging. In the case of ethylene—propylene—diene monomer (EPDM), the curing step occurs before the membrane is ready for packaging. The curing process is accomphshed by placing the membrane in a large vulcanizer where the material is heated under pressure to complete the cure. 

CSPE. Chlorosulfonated polyethylene (CSPE), a synthetic mbber manufactured by DuPont, is marketed under the name Hypalon. It can be produced as a self-curing elastomer designed to cure on the roof. The membrane is typically reinforced with polyester and is available in finished thicknesses of 0.75 to 1.5 mm. Because CSPE exhibits thermoplastic characteristics before it cures, it offers heat-weldable seams. After exposure on the roof, the membrane cures offering the toughness and mechanical set of a thermoset. The normal shelf life of the membrane for maintaining this thermoplastic characteristic is approximately six months. After the membrane is fully cured in the field, conventional adhesives are needed to make repairs. 

Natural mbber comes generally from southeast Asia. Synthetic mbbers are produced from monomers obtained from the cracking and refining of petroleum (qv). The most common monomers are styrene, butadiene, isobutylene, isoprene, ethylene, propylene, and acrylonitrile. There are numerous others for specialty elastomers which include acryUcs, chlorosulfonated polyethylene, chlorinated polyethylene, epichlorohydrin, ethylene—acryUc, ethylene octene mbber, ethylene—propylene mbber, fluoroelastomers, polynorbomene, polysulftdes, siUcone, thermoplastic elastomers, urethanes, and ethylene—vinyl acetate. 

NR = natural mbbei SBR = styiene—butadiene mbbei EPDM = ethylene—piopjiene—diene monomer CSM = chlorosulfonated polyethylene and PE = 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). 

It is estimated that 27,000 t/yr of CSM have been commercially used in the United States. However, due to environmental problems in the manufacturing process, it has been necessary to develop a process that is much mote expensive. As a result many companies using CSM ate trying to replace the CSM with CPE or other elastomers. The result is a decline in the usage of this polymer. Chlorosulfonated polyethylene is sold under the trade name Hypalon (DuPont—Dow Company). 

Meta.1 Oxides. Halogen-containing elastomers such as polychloropreae and chlorosulfonated polyethylene are cross-linked by their reaction with metal oxides, typically ziac oxide. The metal oxide reacts with halogen groups ia the polymer to produce an active iatermediate which then reacts further to produce carbon—carbon cross-links. Ziac chloride is Hberated as a by-product and it serves as an autocatalyst for this reaction. Magnesium oxide is typically used with ZnCl to control the cure rate and minimize premature cross-linking (scorch). 

Isomer mixtures are generally obtained. Chlorosulfonation is used to produce chlorosulfonated polyethylene, a curable thermoplastic. Preformed sulfuryl chloride may also be used. 

Hypalon chlorosulfonated polyethylene good poor poor... 

Ozonc-rcsjstant elastomers which have no unsaturation are an exceUent choice when their physical properties suit the appHcation, for example, polyacrylates, polysulfides, siHcones, polyesters, and chlorosulfonated polyethylene (38). Such polymers are also used where high ozone concentrations are encountered. Elastomers with pendant, but not backbone, unsaturation are likewise ozone-resistant. Elastomers of this type are the ethylene—propylene—diene (EPDM) mbbers, which possess a weathering resistance that is not dependent on environmentally sensitive stabilizers. Other elastomers, such as butyl mbber (HR) with low double-bond content, are fairly resistant to ozone. As unsaturation increases, ozone resistance decreases. Chloroprene mbber (CR) is also quite ozone-resistant. 

Chlorosulfonated polyethylene. Ethylene—acrylic elastomers. Ethylene—propjiene—diene mbber, Eluorocarbon elastomers. 

Prior to butyl mbber, the known natural and synthetic elastomers had reactive sites at every monomer unit. Unlike natural mbber, polychloroprene, and polybutadiene, butyl mbber had widely spaced olefin sites with aHyUc hydrogens. This led to the principle of limited functionahty synthetic elastomers that was later appHed to other synthetic elastomers, eg, chlorosulfonated polyethylene, siUcone mbber, and ethylene—propylene terpolymers. 

These conclusions are further suppo] ted by expected physical properties of dried film of chlorosulfonated polyethylene from the different types of ... 

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