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US5223545A
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US
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Polyethylene terephthalate foams with integral crystalline skins
Assignee: University of Washington
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Filing: 1992-10-09
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Granted: 1993-06-29
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Expires: 2012-10-09
Abstract
Abstract Polyethylene terephthalate composite structures having integral crystalline skins on a foam of polyethylene terephthalate are described. The structures exhibit enhanced physical properties compared to polyethylene terephthalate foams. The structures are produced by a method that crystallizes a portion of the polyethylene terephthalate before foaming the uncrystallized portions of the structure.
Inventors
- 👤 Vipin Kumar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 02:47
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/34; C08J9/04; C08J9/12; C08J9/122; C08J2367/00; C08J2367/02
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
74 words
A method for producing a crystalline feature on a polyethylene terephthalate foam, the method comprising the steps of: exposing polyethylene terephthalate to carbon dioxide gas for a period of time effective to induce crystallization at the surface of the polyethylene terephthalate, the crystallized surface having a weight percent crystallinity of at least about 19 percent; initiating cell growth in the portion of the polyethylene terephthalate that has not crystallized; and quenching the cell growth.
Claim 2
Independent Claim
74 words
A method for producing a crystalline feature on a polyethylene terephthalate foam, the method comprising the steps of: exposing polyethylene terephthalate to carbon dioxide gas for a period of time effective to induce crystallization at the surface of the polyethylene terephthalate, the crystallized surface having a weight percent crystallinity of at least about 19 percent; initiating cell growth in the portion of the polyethylene terephthalate that has not crystallized; and quenching the cell growth.
Claim 3
Dependent Claim
26 words
The method of claim 1, wherein the polyethylene terephthalate is exposed to the carbon dioxide gas for a period of time at least about 190 hours.
Claim 4
Dependent Claim
31 words
The method of claim 2, wherein the polyethylene terephthalate is exposed to the carbon dioxide gas for a period of time in the range of about 190 to about 350 hours.
Claim 5
Dependent Claim
28 words
The method of claim 1, wherein the polyethylene terephthalate is exposed to the carbon dioxide gas at a temperature in the range of about 20° to 30° C.
Claim 6
Dependent Claim
32 words
The method of claim 4, wherein the crystallization of the polyethylene terephthalate proceeds at a rate of about 1 millimeter per 100 hours of exposure to carbon dioxide gas at room temperature.
Claim 7
Dependent Claim
20 words
The method of claim 5, wherein the crystallization of the polyethylene terephthalate proceeds inward from the surface of the article.
Claim 8
Dependent Claim
28 words
The method of claim 1, wherein the polyethylene terephthalate is exposed to the carbon dioxide gas at a pressure in the range of about 40 to 60 atmospheres.
Claim 9
Dependent Claim
28 words
The method of claim 1, wherein initiating cell growth in the uncrystallized polyethylene terephthalate comprises heating the polyethylene terephthalate to a temperature sufficient to initiate the cell growth.
Claim 10
Dependent Claim
32 words
The method of claim 8, wherein initiating cell growth in the uncrystallized polyethylene terephthalate comprises heating the polyethylene terephthalate to a temperature above the glass transition temperature of the uncrystallized polyethylene terephthalate.
Claim 11
Dependent Claim
28 words
The method of claim 9, wherein the temperature sufficient to initiate cell growth in the uncrystallized polyethylene terephthalate is in the range of about 70° to 120° C.
Claim 12
Dependent Claim
22 words
The method of claim 1, wherein quenching of the cell growth in the uncrystallized polyethylene terephthalate further comprises cooling the polyethylene terephthalate.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-06-28 | 1996-12-28 | 1997-06-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-06-28 | 2000-12-28 | 2001-06-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-06-28 | 2004-12-28 | 2005-06-29 | $7700.00 | Window Closed / Lapsed |