Claims
- 1. An ethylene polymer foam structure, comprising: an ethylene polymer material comprising a substantially linear ethylene polymer having:
- a) a melt flow ratio, I.sub.10 /I.sub.2, .gtoreq.5.63;
- b) a molecular weight distribution, M.sub.w /M.sub.n, defined by the equation: M.sub.w /M.sub.n .gtoreq.(I.sub.10 /I.sub.2)-4.63; and
- c) a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear olefin polymer having about the same I.sub.2 and M.sub.w /M.sub.n.
- 2. The Foam structure of claim 1, wherein the M.sub.w /M.sub.n is about 3.5 or less.
- 3. The foam structure of claim 1, wherein the M.sub.w /M.sub.n is from about 1.5 to about 2.5.
- 4. The foam structure of claim 1, wherein the substantially linear ethylene polymer having from about 0.01 to about 3 long chain branches/1000 carbons along the polymer backbone.
- 5. The foam structure of claim 4, having about 0.01 to about 1 long chain branches/1000 carbons along the polymer backbone.
- 6. The foam structure of claim 4, having about 0.05 to about 1 long chain branches/1000 carbons along the polymer backbone.
- 7. The foam structure of claim 1, wherein the substantially linear ethylene polymer is an ethylene/alpha-olefinic copolymer.
- 8. The foam structure of claim 7, wherein the substantially linear ethylene polymer is a copolymer of ethylene monomer and a comonomer selected from the group consisting of 1-octene, 1-butene, 1-hexene, and 4-methyl-1-pentene.
- 9. The foam structure of claim 1, wherein the substantially linear ethylenic polymer is an ethylene homopolymer.
- 10. The foam structure of claim 1, wherein the foam composition is 80 percent or more closed-cell.
- 11. The foam structure of claim 1, wherein the foam composition has a density of less than 250 kilograms per cubic meter.
- 12. The foam structure of claim 1, wherein the ethylene polymer material comprises greater than 70 percent by weight of ethylenic monomeric units.
- 13. The foam structure of claim 1, wherein the foam composition is an extruded foam composition.
- 14. The foam structure of claim 1, wherein the I.sub.10 /I.sub.2 is about 8 or more.
- 15. The foam structure of claim 1, wherein the I.sub.10 /I.sub.2 is about 9 or more.
- 16. The foam structure of claim 1, wherein the rheological processing index is less than or equal to 70 percent of that of a linear ethylene polymer which lacks long-chain branching at about the same I.sub.2 and M.sub.w /M.sub.n.
- 17. The foam structure of claim 1, wherein the ethylene polymer material further comprises a low density polyethylene.
- 18. The foam structure of claim 1, wherein the ethylene polymer material further comprises a linear low density polyethylene.
- 19. The foam structure of claim 1, wherein the ethylene polymer material further comprises an ethylene/acrylic acid copolymer.
- 20. The foam structure of claim 1, wherein the foam structure comprises a blowing agent selected from the group consisting of isobutane, 1,1-difluoroethane, and mixtures of the foregoing.
- 21. The foam structure of claim 1, wherein the ethylene polymer material comprises greater than 50 percent by weight ethylene monomeric units.
- 22. The foam structure of claim 1, wherein the foam structure is in the form of a foam bead.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. Ser. No. 08/054,330, filed Apr. 28, 1993, which is a continuation-in-part of U.S. Ser. No. 08/032,917, filed Mar. 18, 1993, now abandoned. Related applications include U.S. Ser. Nos. 07/939,281, filed Sep. 2, 1992 and 07/776,130, filed Oct. 15, 1991.
US Referenced Citations (7)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0206794A1 |
Dec 1986 |
EPX |
Continuations (1)
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Number |
Date |
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Parent |
54330 |
Apr 1993 |
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Continuation in Parts (1)
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Number |
Date |
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Parent |
32917 |
Mar 1993 |
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