Cyclized Rubber, Particularly Halide Transformations

Boron trifluoride or materials which give rise thereto effect a “cyclization” of rubber in solution: that is, the product is less unsaturated than the original rubber. A particular degree of conversion has been shown to give a tough material, which produces strongly adherent films possessing a high degree of alkali-resistance. When used as a paint medium the material acts as an unsaponifiable “breather” and pigment protector, allowing (unlike “sealers”) the passage of aqueous solutions. For this reason it appears suitable for use on plaster and concrete. Analysis of the purified product indicates appreciable oxidation at some stage and it may be further oxidized by aging at raised temperature or by reagents such as hydrogen peroxide. The oxidation products are not identical. The conversion product yields also a hard vulcanized product resembling hard vulcanized rubber, but less thermoplastic and containing less sulfur than hard rubber produced under the same conditions. This work has been carried out on behalf of the Rubber Producers' Research Association, to whom the authors are indebted for permission to publish.