Vulcanized (per) fluoroelastomer sealing articles

1. A sealing article comprising a vulcanized (per)fluoroelastomer composition incorporating particles of a semicrystalline thermoplastic fluoropolymer chosen from vinylidene fluoride (VDF) homopolymers and copolymers of VDF with one or more monomers containing at least one unsaturation of ethylenic type, in which the sum of the comonomers other than VDF is ≦15 mol % relative to the total amount of monomers in the copolymer, the amount of semicrystalline thermoplastic fluoropolymer being between 30% and 90% by weight relative to the total weight of the (per)fluoroelastomer and of the semicrystalline thermoplastic fluoropolymer, the vulcanized composition having a Shore A hardness of at least 85 when determined according to ASTM D 2240 Type A Durometer method, and a compression set of less than 30%, when determined according to ASTM D395 at 200° C. for 70 h on O-ring according to ASTM D1414.

2. The sealing article according to claim 1 , wherein the amount of semicrystalline thermoplastic fluoropolymer is between 30% and 80% by weight relative to the (per)fluoroelastomer.

3. The sealing article according to claim 1 , wherein the semicrystalline thermoplastic fluoropolymer particles are between 10 and 500 nm in size.

4. The sealing article according to claim 1 , wherein the semicrystalline thermoplastic polymer is a VDF homopolymer or a copolymer of VDF with one or more fluorinated comonomers selected from the group consisting of:

(a) C 2 -C 8 perfluoroolefins;

(b) C 2 -C 8 hydrogenated fluoroolefins;

(c) C 2 -C 8 chloro- and/or bromo- and/or iodo-fluoroolefins;

(d) (per)fluoroalkyl vinyl ethers (PAVE) CF 2 ═CFOR f , in which R f is a C 1 -C 6 (per)fluoroalkyl;

(e) (per)fluorooxyalkyl vinyl ethers CF 2 ═CFOX, in which X is: a C 1 -C 12 ((per)fluoro)-oxyalkyl containing one or more ether groups;

(f) (per)fluorodioxoles of formula:

in which each of the groups R f3 , R f4 , R f5 and R f6 , which may be identical or different from each other, is, independently, a fluorine atom or a C 1 -C 6 perfluoroalkyl group optionally comprising one or more oxygen atoms; and

(g) (per)fluromethoxyvinyl ethers (referred to hereinbelow as: MOVE) having the general formula:

CFX 2 ═CX 2 OCF 2 OR″ f   (I-Ba)

in which R″ f is selected from the group consisting of linear or branched C 1 -C 6 (per)fluoroalkyls; cyclic C 5 -C 6 (per)fluoroalkyls; and linear or branched C 2 -C 6 (per)fluorooxyalkyls, containing from one to three oxygen atoms, and X 2 is F or H.

5. The sealing article according to claim 1 , wherein the (per)fluoroelastomer is selected from the group consisting of:

(1) VDF-based copolymers, in which VDF is copolymerized with at least one comonomer selected from the group consisting of:

(a) C 2 -C 8 perfluoroolefins;

(b) C 2 -C 8 hydrogenated fluoroolefins;

(c) C 2 -C 8 chloro- and/or bromo- and/or iodo-fluoroolefins;

(d) (per)fluoroalkyl vinyl ethers (PAVE) CF 2 ═CFOR f , in which R f is a C 1 -C 6 (per)fluoroalkyl;

(e) (per)fluorooxyalkyl vinyl ethers CF 2 ═CFOX, in which X is: a C 1 -C 12 ((per)fluoro)-oxyalkyl containing one or more ether groups;

(f) (per)fluorodioxoles of formula:

in which each of the groups R f3 , R f4 , R f5 and R f6 , which may be identical or different from each other, is, independently, a fluorine atom or a C 1 -C 6 perfluoroalkyl group optionally comprising one or more oxygen atoms;

(g) (per)fluromethoxyvinyl ethers (referred to hereinbelow as: MOVE) having the general formula:

CFX 2 ═CX 2 OCF 2 OR″ f   (I-Ba)

in which R″ f is selected from the group consisting of linear or branched C 1 -C 6 (per)fluoroalkyls; cyclic C 5 -C 6 (per)fluoroalkyls; and linear or branched C 2 -C 6 (per)fluorooxyalkyls, containing from one to three oxygen atoms, and X 2 is F or H; and

(h) non-fluorinated C 2 -C 8 olefins (Ol); and

2) TFE-based copolymers, in which TFE is copolymerized with at least one comonomer selected from the group consisting of:

(c) C 2 -C 8 chloro- and/or bromo- and/or iodo-fluoroolefins;

(d) (per)fluoroalkyl vinyl ethers (PAVE) CF 2 ═CFOR f , in which R f is a C 1 -C 6 (per)fluoroalkyl;

(e) (per)fluorooxyalkyl vinyl ethers CF 2 ═CFOX, in which X is: a C 1 -C 12 ((per)fluoro)-oxyalkyl containing one or more ether groups;

(g) (per)fluromethoxyvinyl ethers (referred to hereinbelow as : MOVE) having the general formula:

CFX 2 ═CX 2 OCF 2 OR″ f   (I-Ba)

in which R″ f is selected from the group consisting of linear or branched C 1 -C 6 (per)fluoroalkyls; cyclic C 5 -C 6 (per)fluoroalkyls ; and linear or branched C 2 -C 6 (per)fluorooxyalkyls, containing from one to three oxygen atoms, and X 2 is F or H;

(h) non-fluorinated C 2 -C 8 olefins (Ol); and

(i) perfluoro vinyl ethers containing cyanide groups.

6. The sealing article according to claim 5 , wherein the mole composition of the (per)fluoroelastomer is selected from the group consisting of, 100% being the sum of the mole percentages of the monomers :

(a) vinylidene fluoride (VDF) 35-85%, hexafluoropropene (HFP) 10-45%, tetrafluoroethylene (TFE) 0-30%, perfluoroalkyl vinyl ether (PAVE) 0-15%,

(b) vinylidene fluoride (VDF) 50-80%, perfluoroalkyl vinyl ether (PAVE) 5-50%, tetrafluoroethylene (TFE) 0-30%,

(c) vinylidene fluoride (VDF) 20-30%, non-fluorinated olefins (Ol) C 2 -C 8 10-30%, hexafluoropropene (HFP) and/or perfluoroalkyl vinyl ether (PAVE) 18-27%, tetrafluoroethylene (TFE) 10-30%,

(d) tetrafluoroethylene (TFE) 45-65%, non-fluorinated olefins (Ol) C 2 -C 8 20-55%, vinylidene fluoride 0-30%,

(e) tetrafluoroethylene (TFE) 32-60 mol %, non-fluorinated olefins (Ol) C 2 -C 8 10-40%, perfluoroalkyl vinyl ether (PAVE) 20-40%, (per)fluoromethoxyvinyl ether (MOVE) 0-30%,

(f) tetrafluoroethylene (TFE) 33-75%, perfluoroalkyl vinyl ether (PAVE) 15-45%, vinylidene fluoride (VDF) 5-30%, hexafluoropropene HFP 0-30%,

(g) vinylidene fluoride (VDF) 35-85%, (per)fluoromethoxyvinyl ether (MOVE) 5-40%, perfluoroalkyl vinyl ether (PAVE) 0-30%, tetrafluoroethylene (TFE) 0-40%, hexafluoropropene (HFP) 0-30%.

(h) tetrafluoroethylene (TFE) 50-80%, perfluoroalkyl vinyl ether (PAVE) 20-50%;

(i) tetrafluoroethylene (TFE) 45-65%, non-fluorinated olefins (Ol) C 2 -C 8 20-55%, vinylidene fluoride 0-30%;

(l) tetrafluoroethylene (TFE) 32-60%, non-fluorinated olefins (Ol) C 2 -C 8 10-40%, perfluoroalkyl vinyl ether (PAVE) 20-40%;

(m) tetrafluoroethylene (TFE) 33-75%, perfluoroalkyl vinyl ether (PAVE) 15-45%, vinylidene fluoride (VDF) 5-30%; and

(o) tetrafluoroethylene (TFE) 33-75%, perfluoroalkyl vinyl ether (PAVE) 0-45%, MOVE 15-30%, HFP 0-30%.

7. The sealing article according to claim 1 , wherein the (per)fluoroelastomer comprises monomer units derived from a bis-olefin of general formula:

wherein:

R 1 , R 2 , R 3 , R 4 , R 5 and R 6 , which may be identical or different from each other, are H or C 1 -C 5 alkyls;

Z is a linear or branched C 1 -C 18 alkylene or cycloalkylene radical, optionally containing oxygen atoms, or a (per)fluoropolyoxyalkylene radical.

8. The sealing article according to claim 7 , wherein the amount of recurring units derived from the bis-olefin is between 0.01 and 1.0 mol per 100 mol of the other monomer units of the (per)fluoroelastomer.

9. A process for manufacturing the sealing article according to claim 1 , said process comprising

providing a (per)fluoroelastomer composition incorporating particles of a semicrystalline thermoplastic fluoropolymer chosen from vinylidene fluoride (VDF) homopolymers and copolymers of VDF with one or more monomers containing at least one unsaturation of ethylenic type, in which the sum of the comonomers other than VDF is ≦15 mol % relative to the total amount of monomers in the copolymer, the amount of semicrystalline thermoplastic fluoropolymer being between 30% and 90% by weight relative to the total weight of the (per)fluoroelastomer and of the semicrystalline thermoplastic fluoropolymer;

vulcanizing-molding said composition to yield shaped pre-formed sealing articles, and

thermally post-treating said shaped pre-formed sealing articles at a temperature greater than or equal to the melting point of the semicrystalline thermoplastic fluoropolymer.

10. The process of claim 9 , said process comprising vulcanizing-molding at a temperature lower than 160° C.

11. The process of claim 9 , said process comprising thermal post-treating for a time from at least two minutes to 24 hours.

12. The process of claim 9 , said process comprising thermal post-treating at a temperature greater than 160° C.