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US 5,358,675 AGranted
Controlling heterogeneous nucleation and growth of foams
AssigneeMobil Oil Corporation
InventorsGregory A. Campbell, Don H. Rasmussen
Life of this patent
Estimating the term…
Abstract
A method of controlling the nucleation of cells in a polymeric foam material includes blending a matrix material with a second phase material which provides sites for bubble nucleation. The selection of the second phase material controls the size and density of the cells.
Claims44
A method for producing closed cell foamed structures, comprising:
- blending a polymeric matrix material with a second phase material which has a transition temperature below that of said polymeric matrix material to form an unfoamed composition, said second phase material being present in said unfoamed composition in a concentration between 0.001 and 18 volume percent;
- heating said unfoamed composition to a temperature above the transition temperature of the matrix material;
- cooling said unfoamed composition to a temperature below the transition temperature of the polymeric matrix material to provide sites which can be activated for bubble nucleation, whereby said sites are provided by voids resulting from stresses caused by differing thermal expansion coefficients between the second phase material and the polymeric phase material;
- impregnating said unfoamed composition with gas at an elevated pressure;
- and
- heating said impregnated unfoamed composition to expand cells at said sites to form a foamed structure.
3 more elements
A method of producing foamed structures with predictable cell size and density, comprising:
- blending a polymeric matrix material selected from the group consisting of polyester, polyethylene, polystyrene acrylo nitril, polyphenylene oxide/polystyrene, polycarbonate, polyetherimide, polypropylene, nylon and teflon with a second phase material having a lower transition temperature than said matrix material, said second phase material being present in said blend at a concentration of from 0.001 to 18 volume percent of said blend;
- heating said blend to a temperature above the transition temperature of the matrix material;
- cooling said heated blend to a temperature below the transition temperature of the polymeric matrix material to provide sites which can be activated for bubble nucleation, whereby said sites are provided by voids resulting from stresses caused by differing thermal expansion coefficients between the second phase material and the polymeric matrix material;
- impregnating said blend with gas at an elevated pressure;
- and
- heating said impregnated blend to expand cells at said sites to form a foamed structure.
3 more elements
A method of producing foamed structures with predictable cell size and density, comprising:
- blending a polymeric matrix material with a second phase material to form an unfoamed composition, said second phase material having a preselected particle size and a transition temperature below that of said polymeric matrix material, said second phase material being present in said unfoamed composition at a concentration between 0.001 and 18 volume percent;
- heating said unfoamed composition to a temperature above the transition temperature of the matrix material;
- cooling said heated unfoamed composition to a temperature below the transition temperature of the polymeric matrix material to provide sites which can be activated for bubble nucleation, whereby said sites are provided by voids resulting from stresses caused by differing thermal expansion coefficients between the second phase material and the polymeric matrix material;
- impregnating said unfoamed composition with gas at an elevated pressure;
- reducing said process pressure;
- and
- heating said impregnated material to a process temperature to expand said cells to a size dependent on the particle size of the second phase material, thereby foaming the material.
4 more elements
A method for producing a microcellular foamed polymer composition comprising:
- (a) providing a matrix polymeric material;
- (b) blending a second phase material having a particle size of from 0.02 to 10 microns and having a transition temperature below the transition temperature of said matrix polymeric material with said matrix polymeric material to form an unfoamed composition, said second phase material being present in an amount of from 0.001 to 18 volume percent of said unfoamed composition;
- (c) heating said unfoamed composition to a temperature above the transition temperature of the matrix polymeric material;
- (d) cooling said heated unfoamed composition to a temperature below the transition temperature of the matrix polymeric material to provide sites that can be activated for bubble nucleation, whereby said sites are provided by voids resulting from stresses caused by differing thermal expansion coefficients between the second phase material and the matrix polymeric material;
- (e) impregnating said cooled unfoamed composition with a gas at an elevated pressure;
- and
- (f) heating said impregnated unfoamed composition to expand cells at said sites to form the foamed polymer composition.
4 more elements
Dependencies are inferred from the claim text.