Crosslinking halogen-containing polymer

No.l 1, Nov. 1997, p. 19-24 THIADIAZOLES FOR CROSSLINKING HALOGEN-CONTAINING POLYMERS OhmRF... 

Dimercapto-l,3,4-thiadiazole and its derivatives can be used to crosslink a wide variety of halogen-containing polymers. SuccessM use of the thiadiazole in a given polymer is seen to depend on the particular derivative and any associated accelerator. A review is presented of the various thiadiazoles for crosslinking halogen-containing polymers. 3 refs. 

Di- and poly-fimctional mercaptans have been used for many years to crosslink polymers with labile halogens (chlorine or bromine). 2,5-Dimercapto-l,3,4-thiadiazole (DMTD) is one such crosslinker that displays relatively fast cures but poor scorch safety. Improved scorch safety can be achieved by derivatising one or both mercapto groups. Several derivatives of DMTD have been developed recently for this purpose. Proper selection of the thiadiazole derivative and associated accelerator is often a key to successftil use in a given halogen-containing polymer compound. The various... 

The purpose of the present review is the application of the previously mentioned models for the description of a specific type of polymerisation - formation of crosslinked networks of epoxy polymers. It will be made using as example two series of halogen containing epoxy polymers [28]. 

A new synthetic technique for making AB crosslinked copolymers systematically was reported by Bamford et al (1971, 1974). His synthesis involves crosslinking of a suitable polymer (I) with chains of vinyl polymer (II) by reaction of halogen-containing groups in I with an organometallic derivative, e.g., Mo(CO)6 or Mn2(CO)io, in the presence of monomer II. The reaction scheme may be written as... 

Properties Liq. m.w. 208.33 dec. 180 C Uses Crosslinking agent for elastomers, resins initiator for curing polyester resins finishing initiator for styrenics a synergist for some halogen-containing flame retardants polymer modifier... 

A rare example of electropolymerisation employed for the formation of an anion selective crosslinked polymer matrix was introduced by Kamata et al. [153,154]. Reductive coupling between trifunctional p-cyanopyridinium crosslinkers (Fig. 15) in water containing the required counteranion led to stable polymer networks which showed thermodynamic and kinetic anion selectivity. A size exclusion effect was observed whereby only the imprint halogen (and any smaller halogen anion) was electrochemically recognised. Diffusion of the counterion was reduced in the case of the same template anion MIP, but increased with the size of the templating anion. Experiments clearly demonstrating anion selectivity have yet to be carried out. 

Polyacrylic elastomer is a chemically saturated polymer of acrylic acid esters. Since esters are rather inert, other groups such as epoxy, halogen and carboxyl must be incorporated into the polymer to introduce sites for curing. We have studied the effect of various ammonium and phosphonium salt catalysts on the rate of crosslinking of polyacrylic elastomers which contain carboxyl and epoxy groups as cure-sites. We find that the catalytic activity of onium salts correlates with nucleophilicity of their anions. 

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