Polyvinylidenefluoride having high mechanical properties and high thermochemical stability and the preparation process thereof

Process for preparing a polyvinylidene fluoride homopolymer consisting essentially of:

• polymerizing vinylidene fluoride in an aqueous emulsion in the presence of a non-hazardous organic peroxide selected from dialkylperoxides, dialkylperoxycarbonates, dibenzoyl peroxide, t-alkylperoxybenzoates and t-alkylperoxyprivalates wherein said peroxides have a self-accelerating decomposition temperature (SADT) greater than 50.degree. C.;
• a chain transfer agent at a temperature between 95.degree. C. and 120.degree. C.;
• feeding said chain transfer agent into the reactor continuously or in discrete amounts during polymerization;
• and
• recovering a polyvinylidene fluoride homopolymer having a head-to-head and tail-to-tail inversion content between 5 and 5.5 % by mols, a yield point greater than 50 MPa and an elastic modulus greater than 1500 MPa (measured at 23.degree. C. according to ASTM-D-1708 method), a Melt Flow Index (MFI measured at 230.degree. C with a 5 kg load according to ASTM-D-1238 Method) between 1 and 25 g/10' and thermochemical stability to dehydrofluorination.