Processing-coadjuvating additives for rubbers vulcanizable by means of peroxides

A composition containing a peroxide and a rubber or a rubber mixture vulcanizable by means of a peroxidic or a mixed peroxidic and ionic vulcanizing system having improved processability properties, said rubber and rubber mixture being selected from the group consisting of:

• (a) copolymers of CH.sub.2 .dbd.CF.sub.2 with C.sub.3 F.sub.6, and optionally C.sub.2 F.sub.4, containing peroxy crosslinking sites;
• (b) copolymers of C.sub.2 F.sub.4 with propylene;
• (c) copolymers of C.sub.2 F.sub.4 with perfluoroalkylperfluorovinylethers, containing peroxy crosslinking sites;
• (d) terpolymers of CH.sub.2 .dbd.CF.sub.2, C.sub.3 F.sub.6, and a perfluoroalkylperfluorovinyl ether, containing peroxy crosslinking sites;
• (e) a mixture of a fluoroelastomer based on CH.sub.2 .dbd.CF.sub.2 and a copolymer of C.sub.2 F.sub.4 with C.sub.3 H.sub.6 ;
• said composition comprising, as processing co-adjuvant, a brominated additive, in amounts ranging from 0.01 to 5 parts by weight of rubber or rubber mixture or a non-brominated additive, in amounts ranging from 0.5 to 1 part by weight of rubber or rubber mixture or a mixture of a brominated additive in the abovesaid amount with a non-brominated additive, in the abovesaid amount, each of said additives having a mean molecular weight ranging from 500 to 10,000;
• the brominated additive being selected from compounds of formula ##STR7## in which:
• T=F or CF.sub.3 ;
• m, n and q are integers including zero;
• m.sup.+ n.sup.+ q are between 2 and 200;
• m/(n+q).ltoreq.50 when n and/or q are different from zero;
• when m=0, q/n is .gtoreq.0.2 and .ltoreq.20 when n is different from zero;
• when q=0, m/n ranges from 1 to 50 when n is different from zero;
• A and B, either like or unlike each other, consist of a group selected from --CF.sub.2 X, --CF.sub.2 --CF.sub.2 --X, ##STR8## --CF.sub.2 --CFX--CF.sub.3, --COF, --CF.sub.2 --COF, and ##STR9## X being bromine or fluorine, when m is different from 0, X is bromine only in A or in B;
• the non-brominated additive being selected from:
• (a) non-brominated compounds of formula (I) wherein X is fluorine;
• and
• (b) F(CF.sub.2 CF.sub.2 CF.sub.2 O).sub.n --CF.sub.2 CF.sub.3 (II) where n is an integer greater than 2 and lower than 200;
• the mixture of a brominated additive with a non-brominated additive being selected from the mixture of the brominated additive of formula (I) where X is bromine or fluorine with the non-brominated additive of formula (I) where X is fluorine and the mixture of the brominated additive of formula (I) where X is bromine or fluorine with non-brominated additive of formula (II).