Claims
- 1. A method for providing a uniformly dense expanded polymeric body, comprising the steps of:
providing a first polymer material consisting essentially of partially expanded thermally expandable microballoons and a second polymer material consisting essentially of unexpanded thermally expandable microballoons; combining said first and second polymer materials in respective first and second fractions in order to provide a polymer mixture having a predetermined bulk density; dispensing a portion of said polymer mixture into an internal volume of a mold such that said polymer mixture displaces essentially all of said internal volume; closing said mold; heating said mold to a temperature above a polymer glass transition temperature for about one hour, said temperature causing said partially expanded and said unexpanded microballoons to soften and expand to fill the interstitial spaces between each of said microballoons, said temperature further causing surfaces of adjoining microballoon to fuse together providing thereby an expanded polymeric body; cooling said mold to a temperature below less than 80° C.; and removing said expanded polymeric body from said mold to provide said molded body.
- 2. The method of claim 1, wherein the bulk predetermined density is selected in the range of between about 0.013 g/cm3 to about 0.5 g/cm3.
- 3. The method of claim 1, wherein the step of combining further includes mixing said first and second polymer materials in a mixing jar, wherein said jar has internal baffles or helical fins for mixing said materials.
- 4. The method of claim 3, wherein said mixing jar is rotated on a rotary mill for about at least 3 hours.
- 5. The method of claim 1, wherein said temperature is a temperature selected between about 130° C. to about 150° C.
- 6. The method of claim 1, wherein said temperature is about 150° C.
- 7. The method of claim 1, wherein the step of closing further comprises non-hermetically sealing said mold.
- 8. The method of claim 1, wherein the thermally expandable microballoons comprise a mixture of polyacrylonitrile, polymethacrylonitrile, and iso-pentane.
- 9. A uniformly dense molded polymeric body made by a process comprising the steps of:
providing a first polymer material consisting essentially of partially expanded thermally expandable microballoons and a second polymer material consisting essentially of unexpanded thermally expandable microballoons; combining said first and second polymer materials in respective first and second fractions in order to provide a polymer mixture having a predetermined bulk density; dispensing a portion of said polymer mixture into, an internal volume of a mold such that said polymer mixture displaces essentially all of said internal volume; closing said mold; heating said polymer mixture to a temperature above a polymer glass transition temperature for period for about one hour, said temperature causing said partially expanded and said unexpanded microballoons to soften and expand to fill the interstitial spaces between each of said microballoons, said temperature further causing surfaces of adjoining microballoon to fuse together to provide said molded polymeric body; cooling said mold to a temperature below less than 80° C.; and removing said molded polymeric body from said mold, said molded polymeric body having a bulk density varying by less than about ±6% everywhere within said body.
- 10. The molded polymeric body of claim 9, wherein the predetermined bulk density is selected in the range of between about 0.013 g/cm3 to about 0.5 g/cm3.
- 11. The molded polymeric body of claim 9, wherein the step of combining further includes mixing said first and second polymer materials in a mixing jar, wherein said jar has internal baffles or helical fins for mixing said materials.
- 12. The molded polymeric body of claim 11, wherein said mixing jar is rotated on a rotary mill for about at least 3 hours.
- 13. The molded polymeric body of claim 9, wherein said temperature is a temperature selected between about 130° C. to about 150° C.
- 14. The molded polymeric body of claim 9, wherein said temperature is about 150° C.
- 15. The molded polymeric body of claim 9, wherein the step of closing further comprises non-hermetically sealing said mold.
- 16. The molded polymeric body of claim 9, wherein the thermally expandable microballoons comprise a mixture of polyacrylonitrile, polymethacrylonitrile, and iso-pentane.
- 17. A molded polymeric, body comprising a density varying by less than about ±6% everywhere throughout said molded body.
- 18. The molded polymeric body of claim 17, wherein the thermally expandable microballoons comprise a mixture of polyacrylonitrile, polymethacrylonitrile, and iso-pentane
STATEMENT OF GOVERNMENT INTEREST
[0001] This invention was made with support under United States Government contract no. DE-AC04-94AL85000 awarded by the U.S. Department of Energy to Sandia Corporation. The Government has certain rights in the invention.
Divisions (1)
|
Number |
Date |
Country |
Parent |
09916844 |
Jul 2001 |
US |
Child |
10210534 |
Jul 2002 |
US |