Additives for fluorinated oils

A perfluoropolyether compound of formula:

• wherein
• Rf is a (per) fluoropolyoxyalkylene chain formed of one or more repeating units, statistically placed along the chain, having the following structure:
• (CFXO), (CF2CF2O), (CF2CF2CF2O), (CF2CF2CF2CF2O), (CR6R7CF2CF2O), (CF(CF3)CF2O), (CF2CF(CF3)O), wherein X=F, CF3;
• R6 and R7, equal to or different from each other, are selected from H, Cl, or perfluoroalkyl from 1 to 4 carbon atoms, said Rf having a number average molecular weight in the range 500-10,000;
• W1, W2, equal to or different from each other, are —F or —CF3;
• T1 is equal to —CHAa—Ba (CH2CH2O)na— wherein Aa═H, CF3;
• Ba═O, S, NH;
• na is an integer from 0 to 6, extremes included;
• T2 is equal to —F, —CF3, —C2 F5, —(C2F4)Cl, or a group of formula:
• Q1, Q2, equal to or different from each other, are a perfluoropolyoxyalkylene chain of formula:
• -T1-CFW1—O—Rf—CFW2-T′2,
• wherein T′2 is equal to —F, —CF3, —C2F5,
• (C2 F4)Cl;
• T1, W1 and W2 have the above meaning;
• or a group of formula:
• wherein B is equal to O, S, NH;
• R1, R2, R3, R4, R5, equal to or different from each other, are selected from H, F, NO2, CN, linear or branched C1-C8 perfluoroalkyl, carboxyl, phenyl (Ph), O-Ph, NH-Ph, S-Ph;
• with the proviso that at least one of Q1 and Q2 is equal to: