Polyolefin elastomer compositions and methods of making the same
An elastomeric article is provided that includes a composition having a silane-crosslinked polyolefin elastomer with a density less than 0.90 g/cm 3 . The elastomeric article 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 silane-crosslinked polyolefin elastomer 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 propylene/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 elastomer 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.) and wherein the silane-crosslinked polyolefin elastomer blend has a density less than 0.90 g/cm 3 ,
wherein the silane-crosslinked polyolefin elastomer blend is a thermoset,
wherein the silane-crosslinked polyolefin elastomer blend exhibits a crystallinity of from about 5% to about 20%, and
wherein the silane-crosslinked polyolefin elastomer blend does not display a Mullins effect or a Payne effect.
2. The silane-crosslinked polyolefin elastomer blend of claim 1 further comprising a microencapsulated foaming agent.
3. The silane-crosslinked polyolefin elastomer blend of claim 1 , wherein the silane-crosslinked polyolefin elastomer blend comprises from about 3 wt % to about 10 wt % polypropylene filler and has a density is less than 0.70 g/cm 3 .
4. The silane-crosslinked polyolefin elastomer blend of claim 1 wherein the silane-crosslinked polyolefin elastomer blend exhibits a crystallinity of from about 5% to about 10%.
5. The silane-crosslinked polyolefin elastomer blend of claim 1 , wherein the silane-crosslinked polyolefin elastomer blend comprises from about 3 wt % to about 10 wt % polypropylene filler and has a density is less than 0.60 g/cm 3 .
6. The silane-crosslinked polyolefin elastomer blend 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.).
7. The silane-crosslinked polyolefin elastomer blend of claim 1 , wherein the silane-crosslinked polyolefin blend comprises from about 30 wt. % to about 70 wt. % of the first polyolefin.
8. The silane-crosslinked polyolefin elastomer blend of claim 1 , wherein the second polyolefin is a blend of propylene/α-olefin copolymer with an ethylene/α-olefin copolymer and the second polyolefin comprises from about 20 wt % to about 40 wt % of the silane-crosslinked polyolefin elastomer blend.
9. The silane-crosslinked polyolefin elastomer blend of claim 1 , wherein the silane crosslinks are derived from vinyltrimethoxy silane and/or a vinyltriethoxy silane crosslinkers present in an amount of from about 0.5 wt. % to about 5 wt. % of the silane-crosslinked polyolefin elastomer blend.
10. A silane-crosslinked polyolefin elastomer 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 propylene/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%;
vinyltrialkoxy silane-based crosslinks;
wherein the silane-crosslinked polyolefin elastomer 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.) and wherein the silane-crosslinked polyolefin elastomer blend has a density less than 0.70 g/cm 3 ,
wherein the silane-crosslinked polyolefin elastomer blend is a thermoset,
wherein the silane-crosslinked polyolefin elastomer blend exhibits a crystallinity of from about 5% to about 20%, and
wherein the silane-crosslinked polyolefin elastomer blend does not display a Mullins effect or a Payne effect.
11. The silane-crosslinked polyolefin elastomer blend of claim 10 , wherein the silane-crosslinked polyolefin blend comprises from about 30 wt. % to about 70 wt. % of the first polyolefin.
12. The silane-crosslinked polyolefin elastomer blend of claim 10 , wherein the second polyolefin is a blend of propylene/α-olefin copolymer with an ethylene/α-olefin copolymer and the second polyolefin comprises from about 20 wt % to about 40 wt % of the silane-crosslinked polyolefin elastomer blend.
13. The silane-crosslinked polyolefin elastomer blend of claim 10 , wherein the vinyltrialkoxy silane-based crosslinks are derived from a vinyltrimethoxy silane and/or vinyltriethyoxy silane crosslinkers present in an amount of from about 0.5 wt. % to about 5 wt. % of the silane-crosslinked polyolefin elastomer blend.
14. The silane-crosslinked polyolefin elastomer blend of claim 10 , further comprising from about 0.25 wt % to about 8 wt % of a condensation catalyst.
15. The silane-crosslinked polyolefin elastomer blend of claim 10 , wherein the silane-crosslinked polyolefin elastomer blend comprises from about 3 wt % to about 10 wt % polypropylene filler and has a density is less than 0.60 g/cm 3 .
16. The silane-crosslinked polyolefin elastomer blend of claim 10 , wherein the silane-crosslinked polyolefin elastomer blend exhibits a crystallinity of from about 5% to about 10% and comprises a microencapsulated foaming agent.
17. The silane-crosslinked polyolefin elastomer blend of claim 10 , wherein the compression set is from about 15.0% to about 35.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.).
18. A method for making an elastomeric article, the method comprising:
extruding 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 crystallinity less than 40% wherein the second polyolefin is a propylene/α-olefin copolymer or a blend of propylene/α-olefin copolymer with an ethylene/α-olefin copolymer; 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, a condensation catalyst and a foaming agent together to form a silane-crosslinkable polyolefin blend;
molding the silane-crosslinkable polyolefin blend into an uncured elastomeric article; and
crosslinking the crosslinkable-polyolefin blend of the uncured elastomeric article at an ambient temperature and an ambient humidity to form the elastomeric article having a density less than 0.70 g/cm 3 ,
wherein the elastomeric article 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 elastomeric article exhibits a crystallinity of from about 5% to about 20%,
wherein the elastomeric article 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 elastomeric article is a thermoset.
19. The method of claim 18 , wherein the amount of polypropylene filler ranges from about 3 wt % to about 10 wt %.
20. The method of claim 18 , wherein the foaming agent is a microencapsulated foaming agent.