Microdense seals, compositions, and methods of making the same
View Patent ↗A microdense sealing member is provided. The microdense sealing member includes a composition having a foamed silane-crosslinked polyolefin elastomer with a density less than 0.70 g/cm 3 . The microdense sealing member can exhibit a compression set of from about 5.0% to about 35.0% measured according to ASTM D 395 (22 hrs @ 70° C.). The foamed silane-crosslinked polyolefin elastomer can be produced from a blend including a first polyolefin having a density less than 0.86 g/cm 3 , a second polyolefin having a crystallinity less than 60° C., a silane crosslinker, a grafting initiator, a condensation catalyst, and a microencapsulated foaming agent.
1. A microdense sealing member comprising:
a composition comprising a foamed silane-crosslinked polyolefin elastomer having a density less than 0.70 g/cm 3 , a tensile strength ranging from 5.0 to 7.6 MPa as measured according to ASTM D412, a Shore A hardness ranging from 60 to 87 as measured according to ASTM D412, and a crystallinity of from about 5% to about 20%,
wherein from about 1 wt % to about 20 wt % of the foamed silane-crosslinked polyolefin elastomer is a polypropylene filler having a crystallinity greater than 40%,
wherein the foamed silane-crosslinked polyolefin elastomer does not display a Mullins effect or a Payne effect;
wherein the foamed silane-crosslinked polyolefin elastomer and the microdense sealing member are thermosets; and
wherein the microdense sealing member exhibits a compression set of from about 40.0% to about 78.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.).
2. The microdense sealing member of claim 1 , wherein the foamed silane-crosslinked polyolefin elastomer 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, a condensation catalyst, and a microencapsulated foaming agent.
3. The microdense sealing member of claim 1 , wherein the foamed silane-crosslinked polyolefin elastomer comprises from about 3 wt % to about 10 wt % polypropylene filler and has a density of from about 0.60 g/cm 3 to about 0.69 g/cm 3 .
4. The microdense sealing member of claim 1 , wherein the foamed silane-crosslinked polyolefin elastomer exhibits a crystallinity of from about 5% to about 10%.
5. The microdense sealing member of claim 1 , wherein the foamed silane-crosslinked polyolefin elastomer exhibits a glass transition temperature of from about −75° C. to about −25° C.
6. The microdense sealing member of claim 1 , wherein the microdense sealing member exhibits a weathering color difference of from about 0.25 ΔE to about 2.0 ΔE, as measured according to ASTM D2244.
7. The microdense sealing member of claim 1 , further comprising:
a coloring agent.
8. A foamed 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 propylene/α-olefin copolymer or a blend of propylene/α-olefin copolymer with an ethylene/α-olefin copolymer;
from about 1 wt % to about 20 wt % polypropylene filler having a crystallinity greater than 40%;
silane crosslinks; and
a microencapsulated foaming agent,
wherein the foamed silane-crosslinked polyolefin blend exhibits a compression set of from about 40.0% to about 78.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.),
wherein the foamed silane-crosslinked polyolefin blend has a density less than 0.70 g/cm 3 ,
wherein the foamed silane-crosslinked polyolefin blend is a thermoset,
wherein the foamed silane-crosslinked polyolefin blend exhibits a crystallinity of from about 5% to about 20%, and
wherein the foamed silane-crosslinked polyolefin blend does not display a Mullins effect or a Payne effect.
9. The foamed silane-crosslinked polyolefin blend of claim 8 , wherein the first polyolefin comprises from about 30 wt % to about 70 wt % of the foamed silane-crosslinked polyolefin blend.
10. The foamed silane-crosslinked polyolefin blend of claim 8 , 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 10 wt % to about 35 wt % of the foamed silane-crosslinked polyolefin blend.
11. The foamed silane-crosslinked polyolefin blend of claim 8 , wherein the silane crosslinks are derived from a vinyltrimethoxy silane crosslinker.
12. The foamed silane-crosslinked polyolefin blend of claim 8 , further comprising from about 0.25 wt % to about 8 wt % of a condensation catalyst.
13. The foamed silane-crosslinked polyolefin blend of claim 8 , wherein the blend comprises from about 3 wt % to about 10 wt % polypropylene filler and has a density from about 0.60 g/cm 3 to about 0.69 g/cm 3 .
14. The foamed silane-crosslinked polyolefin blend of claim 8 , wherein the blend exhibits a crystallinity of from about 5% to about 10%.
15. The foamed silane-crosslinked polyolefin blend of claim 8 , wherein the blend exhibits a glass transition temperature of from about −75° C. to about −25° C.
16. A method for making a microdense 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, a condensation catalyst, and a microencapsulated foaming agent together to form a foamed silane-crosslinkable polyolefin blend;
molding the foamed silane-crosslinkable polyolefin blend into an uncured microdense sealing element; and
crosslinking the foamed silane-crosslinkable polyolefin blend of the uncured microdense sealing element at an ambient temperature and an ambient humidity to form the element into a microdense sealing member having a density from about 0.60 g/cm 3 to about 0.69 g/cm 3 and comprising a foamed silane-crosslinked polyolefin blend,
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 microdense sealing member exhibits a compression set of from about 40.0% to about 78.0%, as measured according to ASTM D 395 (22 hrs @ 70° C.),
wherein the microdense sealing member exhibits a tensile strength ranging from 5.0 to 7.6 MPa as measured according to ASTM D412,
wherein the microdense sealing member exhibits a Shore A hardness ranging from 60 to 87 as measured according to ASTM D412;
wherein the microdense sealing member and the foamed silane-crosslinked polyolefin blend are thermosets,
wherein the foamed silane-crosslinked polyolefin elastomer exhibits a crystallinity of from about 5% to about 20%,
wherein the foamed silane-crosslinked polyolefin blend does not display a Mullins effect or a Payne effect, and
wherein the foamed silane-crosslinkable polyolefin blend exhibits thermoplastic properties.
17. The method of claim 16 , wherein the silane-grafted polyolefin blend and the foamed silane-crosslinkable polyolefin blend are thermoplastics, and the foamed silane-crosslinked polyolefin blend of the microdense sealing member is a thermoset.
18. The method of claim 16 , wherein the foamed silane-crosslinked polyolefin elastomer exhibits a crystallinity of from about 5% to about 10%.
19. The method of claim 16 , wherein the amount of polypropylene filler ranges from about 3 wt % to about 10 wt %.