DYNAMIC SEALS, COMPOSITIONS, AND METHODS OF MAKING THE SAME
A sponge sealing member is provided that includes a composition having a silane-crosslinked polyolefin elastomer with a density less than 0.60 g/cm 3 . The sponge 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 also 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, a condensation catalyst, and a foaming agent.
1 . A sponge sealing member comprising:
a composition comprising a silane-crosslinked polyolefin elastomer having a density less than 0.60 g/cm 3 ,
wherein the sponge 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 sponge sealing member of claim 1 , wherein the silane-crosslinked polyolefin elastomer comprises a first polyolefin having a density less than 0.86 g/cm 3 , a second polyolefin having a percent crystallinity less than 40%, a silane crosslinker, a grafting initiator, a condensation catalyst, and a foaming agent.
3 . The sponge 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 sponge sealing member of claim 1 , wherein the density is from about 0.50 g/cm 3 to about 0.59 g/cm 3 .
5 . The sponge sealing member of claim 1 , wherein the silane-crosslinked polyolefin elastomer exhibits a crystallinity of from about 5% to about 25%.
6 . The sponge 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 sponge sealing member of claim 1 , wherein the composition is a thermoset, but exhibits thermoplastic properties during processing.
8 . The sponge sealing member of claim 1 , wherein the sponge sealing member exhibits a weathering color difference of from about 0.25 ΔE to about 2.0 ΔE, as measured according to ASTM D2244.
9 . The sponge sealing member of claim 1 , further comprising:
a coloring agent.
10 . A foamed silane-crosslinked polyolefin blend comprising:
a first polyolefin having a density less than 0.86 g/cm 3 ;
a second polyolefin having a percent crystallinity less than 40%;
a silane crosslinker; and
a foaming agent,
wherein the foamed 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.), and
wherein the foamed silane-crosslinked polyolefin blend has a density less than 0.60 g/cm 3 .
11 . The foamed silane-crosslinked polyolefin blend of claim 10 , wherein the first polyolefin comprises an ethylene octene copolymer from about 60 wt % to about 97 wt %.
12 . The foamed silane-crosslinked polyolefin blend of claim 10 , wherein the second polyolefin comprises a polypropylene homopolymer from about 10 wt % to about 35 wt % and/or a poly(ethylene-co-propylene).
13 . The foamed silane-crosslinked polyolefin blend of claim 10 , wherein the silane crosslinker comprises a vinyltrimethoxy silane from about 1 wt % to about 4 wt %.
14 . The foamed silane-crosslinked polyolefin blend of claim 10 , further comprising a non-metal condensation catalyst that comprises a sulfonic ester from about 1 wt % to about 4 wt %.
15 . The foamed silane-crosslinked polyolefin blend of claim 10 , wherein the blend has a density from about 0.85 g/cm 3 to about 0.89 g/cm 3 .
16 . The foamed silane-crosslinked polyolefin blend of claim 10 , wherein the blend exhibits a crystallinity of from about 5% to about 25%.
17 . The foamed silane-crosslinked polyolefin blend of claim 10 , wherein the blend exhibits a glass transition temperature of from about −75° C. to about −25° C.
18 . A method for making a sponge 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 silane crosslinker and a grafting initiator together to form a silane-grafted polyolefin blend;
extruding the silane-grafted polyolefin blend, a condensation catalyst, and a foaming agent together to form a foamed silane-crosslinkable polyolefin blend;
molding the foamed silane-crosslinkable polyolefin blend into an uncured sponge sealing element; and
crosslinking the foamed crosslinkable-polyolefin blend of the uncured sponge sealing element at an ambient temperature and an ambient humidity to form the element into a sponge sealing member having a density from about 0.85 g/cm 3 to about 0.89 g/cm 3 comprising a foamed silane-crosslinked polyolefin blend,
wherein the sponge 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.).
19 . The method of claim 18 , wherein the silane-grafted polyolefin blend and the crosslinkable-polyolefin blend are thermoplastics, and the foamed-silane crosslinked polyolefin blend is a thermoset.
20 . The method of claim 18 , wherein the first polyolefin is an ethylene/α-olefin copolymer and the second polyolefin is a polypropylene homopolymer and/or a poly(ethylene-co-propylene).