Static seals, compositions, and methods of making the same
A static sealing member is provided that includes a composition having a silane-crosslinked polyolefin elastomer with a density less than 0.90 g/cm 3 . The static sealing member can exhibit a compression set of from about 5.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.). The silane-crosslinked polyolefin elastomer can include a first polyolefin having a density less than 0.86 g/cm 3 , a second polyolefin having a crystallinity less than 40%, a silane crosslinker, a grafting initiator, and a condensation catalyst.
1. A static sealing member comprising:
a composition comprising a silane-crosslinked polyolefin elastomer having a density less than 0.90 g/cm 3 and a crystallinity of from about 5% to about 20%,
wherein from about 1 wt % to about 35 wt % of the silane-crosslinked polyolefin elastomer is a polypropylene filler having a crystallinity greater than 40%,
wherein the silane-crosslinked polyolefin elastomer does not display a Mullins effect or a Payne effect;
wherein the silane-crosslinked polyolefin elastomer and the static sealing member are thermosets; and
wherein the static sealing member exhibits a compression set of from about 5.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.).
2. The static sealing member of claim 1 , wherein the silane-crosslinked polyolefin elastomer further comprises
a first polyolefin having a density less than 0.86 g/cm 3 , wherein the first polyolefin is an ethylene/α-olefin copolymer,
a second polyolefin having a percent crystallinity less than 40%, wherein the second polyolefin is a polypropylene/α-olefin copolymer or a blend of propylene/α-olefin copolymer with an ethylene/α-olefin copolymer,
a silane crosslinker, a grafting initiator, and a non-metal condensation catalyst.
3. The static sealing member of claim 1 , wherein the compression set is from about 15.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.).
4. The static sealing member of claim 1 , wherein the silane-crosslinked polyolefin elastomer comprises from about 3 wt % to about 10 wt % polypropylene filler and has a density is from about 0.85 g/cm 3 to about 0.89 g/cm 3 .
5. The static sealing member of claim 1 , wherein the silane-crosslinked polyolefin elastomer exhibits a crystallinity of from about 5% to about 10%.
6. The static sealing member of claim 1 , wherein the silane-crosslinked polyolefin elastomer exhibits a glass transition temperature of from about −75° C. to about −25° C.
7. The static sealing member of claim 1 , wherein the static sealing member exhibits a weathering color difference of from about 0.25 ΔE to about 2.0 ΔE, as measured according to ASTM D2244.
8. The static sealing member of claim 1 , further comprising:
a coloring agent.
9. A silane-crosslinked polyolefin blend comprising:
a first polyolefin having a density less than 0.86 g/cm 3 , wherein the first polyolefin is an ethylene/α-olefin copolymer;
a second polyolefin having a percent crystallinity less than 40%, wherein the second polyolefin is a polypropylene/α-olefin copolymer or a blend of propylene/α-olefin copolymer with an ethylene/α-olefin copolymer;
from about 1 wt % to about 35 wt % polypropylene filler having a crystallinity greater than 40%;
and
silane crosslinks;
wherein the silane-crosslinked polyolefin blend exhibits a compression set of from about 5.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.),
wherein the silane-crosslinked polyolefin blend is a thermoset,
wherein the silane-crosslinked polyolefin blend exhibits a crystallinity of from about 5% to about 20%, and
wherein the silane-crosslinked polyolefin blend does not display a Mullins effect or a Payne effect.
10. The silane-crosslinked polyolefin blend of claim 9 , wherein the first polyolefin comprises from about 30 wt % to about 70 wt % of the silane-crosslinked polyolefin blend.
11. The silane-crosslinked polyolefin blend of claim 9 , wherein the silane crosslinks are derived from a vinyltrimethoxy silane crosslinker.
12. The silane-crosslinked polyolefin blend of claim 9 , further comprising from about 0.25 wt % to about 8 wt % of a non-metal condensation catalyst.
13. The silane-crosslinked polyolefin blend of claim 9 , wherein the blend comprises from about 3 wt % to about 10 wt % polypropylene filler and has a density from about 0.85 g/cm 3 to about 0.89 g/cm 3 .
14. The silane-crosslinked polyolefin blend of claim 9 , wherein the blend exhibits a crystallinity of from about 5% to about 10%.
15. The silane-crosslinked polyolefin blend of claim 9 , wherein the blend exhibits a glass transition temperature of from about −75° C. to about −25° C.
16. A method for making a static sealing member, the method comprising:
extruding a first polyolefin having a density less than 0.86 g/cm 3 , a second polyolefin having a crystallinity less than 40%, a polypropylene filler having a crystallinity greater than 40%, a silane crosslinker and a grafting initiator together to form a silane-grafted polyolefin blend, wherein the polypropylene filler comprises from about 1 wt % to about 20 wt % of the silane-grafted polyolefin blend;
extruding the silane-grafted polyolefin blend and a condensation catalyst together to form a silane-crosslinkable polyolefin blend;
molding the silane-crosslinkable polyolefin blend into an uncured static sealing element; and
crosslinking the crosslinkable-polyolefin blend of the uncured static sealing element at an ambient temperature and an ambient humidity to form the element into a static sealing member having a density from about 0.85 g/cm 3 to about 0.89 g/cm 3 ,
wherein the first polyolefin is an ethylene/α-olefin copolymer and the second polyolefin is a propylene/α-olefin copolymer or a blend of propylene/α-olefin copolymer with an ethylene/α-olefin copolymer,
wherein the static sealing member exhibits a compression set of from about 5.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.),
wherein the static sealing member exhibits a crystallinity of from about 5% to about 20%,
wherein the static sealing member does not display a Mullins effect or a Payne effect; and
wherein the silane-grafted polyolefin blend and the silane-crosslinkable polyolefin blend exhibit thermoplastic properties and the static sealing member is a thermoset.
17. The static sealing member of claim 1 , wherein the silane-crosslinked polyolefin elastomer exhibits a tensile strength ranging from 10.4 to 14.5 MPa as measured according to ASTM D412 and a Shore A hardness ranging from 76 to 88 as measured according to ASTM D412.
18. The method of claim 16 , wherein the amount of polypropylene filler ranges from about 3 wt % to about 10 wt %.
19. The method of claim 16 , wherein the static sealing member exhibits a tensile strength ranging from 10.4 to 14.5 MPa as measured according to ASTM D412 and a Shore A hardness ranging from 76 to 88 as measured according to ASTM D412.