Claims
- 1. A method for packaging an article which contains heat-sensitive contents that may be damaged by exposure to temperatures above a predetermined threshold temperature Tt comprising:
selecting an open cellular foam material having a thermal memory characteristic at a glass transition temperature Tg which is approximately equal to or greater than the predetermined threshold temperature of the contents of the article; forming the foam material to an original foamed volume OV; compressing the foam material at an elevated temperature above its glass transition temperature Tg to a selected densified volume DV; cooling the densified foam material to a temperature below its Tg to retain it in the densified state; applying the densified foam material around an article in a carton leaving a free space in the carton, such that when a temperature exceeding the glass transition temperature Tg is applied to the carton with the foam material around the article containing the heat-sensitive contents, the foam material is re-expanded to substantially its original volume OV to indicate exposure to a temperature above the predetermined threshold temperature Tt.
- 2. A method according to claim 1, wherein the free space is equal to the quantity (OV−DV) multiplied by a volume factor Y.
- 3. A method according to claim 2, wherein the volume factor Y is less than 1.0, such that the foam material re-expands to a volume exceeding the available free space inside the carton, resulting in a compressive force on the article and the carton, the compressive force being sufficient to deform the carton so that the deformation is visible externally.
- 4. A method according to claim 2, wherein the volume factor Y is less than 1.0, such that the foam material re-expands to completely fill the available free space inside the carton, resulting in a compressive force on the article, the compressive force being such that the article cannot be readily removed from the carton
- 5. A method according to claim 2, wherein the volume factor Y is equal to or greater than 1.0, such that the foam material re-expands without restraint and the re-expanded foam material provides a visual indicator of exposure to a temperature equal to or greater than Tt.
- 6. A method according to claim 1, wherein the free space is located between the article and the densified foam material.
- 7. A method according to claim 1, wherein the free space is located between a wall of the carton and the densified foam material.
- 8. A method according to claim 6, wherein the densified foam material is in the form of a thin strip inserted along a wall of the carton.
- 9. A method according to claim 7, wherein the densified foam material is in the form of a thin strip inserted adjacent to the article.
- 10. A method according to claim 1, wherein the open cellular foam material is a polyurethane-based thermoplastic polymer.
- 11. A method according to claim 1, wherein the open cellular foam material is produced from butadiene liquid polymer, an activator and sulfur monochloride.
- 12. A method according to claim 1, wherein the re-expanded foam material deforms the carton walls so that the deformation is visible externally.
- 13. A method according to claim 1, wherein the re-expanded foam material presses against the article with sufficient force that it cannot be readily removed from the carton.
- 14. A method for packaging an article which contains heat-sensitive contents that may be damaged by exposure to a temperature above a predetermined threshold temperature Tt comprising:
selecting an open cellular foam material having a thermal memory characteristic at a glass transition temperature Tg which is approximately equal to or greater than the predetermined threshold temperature of the contents of the article; forming the foam material to an original foamed volume OV; compressing it at an elevated temperature above its glass transition temperature Tg to a selected densified volume DV; cooling the densified foam material to a temperature below its Tg to retain it in the densified state; applying the densified foam material to a heat-damage-indicating panel located within a wall of a carton having an inner surface adjacent the article and an outer surface visible externally of the carton which is rupturable by the re-expanded foam material applied to the heat-damage-indicating panel, such that when a temperature exceeding the glass transition temperature Tg is applied to the carton, the foam material in the heat-damage-indicating panel is re-expanded to substantially its original volume OV and thereby ruptures the outer surface of the panel to indicate that the contents of the article may be heat-damaged.
- 15. A method according to claim 14, wherein the open cellular foam material is a polyurethane-based thermoplastic polymer.
- 16. A method according to claim 14, wherein the open cellular foam material is produced from butadiene liquid polymer, an activator and sulfur monochloride.
- 17. A method according to claim 14, wherein the densified foam material is in the form of a thin chip mounted to an internal surface of the heat-damage-indicating panel of the carton adjacent the contents, and the panel has an aperture through which the re-expanded foam material pushes outwardly to provide an external indication of heat damage.
- 18. An indicator for heat damage to an article which contains heat-sensitive contents, comprising:
the carton having a panel formed on a wall thereof in which a heat-detecting element is mounted, said element being open cellular foam material having a thermal memory characteristic at a glass transition temperature Tg which is approximately equal to or greater than a predetermined threshold temperature Tt of the contents of the carton, wherein foam material of the heat detecting element has an original foamed volume OV and is compressed to a densified volume DV; and the panel of the carton having an inner surface mounting the heat-detecting element adjacent the article and an outer surface visible externally of the carton which is rupturable by the foam material when re-expanded by a temperature exceeding the glass transition temperature Tg of the foam material.
- 19. An indicator for heat damage to a packaged article according to claim 18, wherein the panel has an aperture in its external surface and the heat-detecting element in the form of a compressed foam chip mounted at its inner surface adjacent the article.
- 20. An indicator for heat damage to a packaged article according to claim 18, wherein the aperture in the panel is sealed with a transparent film.
- 21. An indicator for heat damage to a packaged article according to claim 18, wherein the aperture in the panel is sealed with a non-transparent, opaque film.
PRIORITY CLAIM
[0001] This application claims the priority date of, and incorporates by reference, pending U.S. Provisional Patent Application No. 60/256,239, which was filed on Dec. 15, 2000.
Provisional Applications (1)
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Number |
Date |
Country |
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60256239 |
Dec 2000 |
US |