Insulating plastic foams based on polyolefins
Embodiments of the present invention encompass methods of forming a foamed polyolefin and articles and materials of the foamed polyolefin. The foamed materials and articles may be used in applications requiring thermal insulation.
1. A method of manufacturing a foamed article or material, the method comprising:
forming a blend composition, the blend composition comprising a polyolefin, a non-encapsulated paraffin wax, a cross-linking agent, and an optional additive material;
executing an operation comprising cross-linking the polyolefin to form a cross-linked intermediate composition wherein the cross-linking results in a cross-linked portion in the range of 20 percent by weight to 35 percent by weight of the polyolefin;
executing an operation comprising foaming the cross-linked intermediate composition to form a foamed article or material; and
laminating a film to at least a portion of an exterior surface of the foamed article or material; wherein the thermal conductivity of the foamed article or material is in the range of 0.07 to 0.12 W/(m*K) and wherein the article or material does not change more than 10% after 20 temperature cycles as measured by differential scanning calorimetry (DSC) wherein each temperature cycle encompasses the transition temperature of the phase change material of the foamed article or material and at least 10° C. on each side.
2. The method of claim 1 , wherein forming the blend composition comprising the polyolefin, the non-encapsulated paraffin wax, the cross-linking agent, and the additive material, if present, comprises mixing the polyolefin, the non-encapsulated paraffin wax, the cross-linking agent, and the additive material, if present, together until homogeneous or substantially homogeneous.
3. The method of claim 2 , wherein the mixing is executed at a temperature in the range of 80° C. to 220° C.
4. The method of claim 1 , wherein
cross-linking comprises exposing the blend composition to an elevated temperature in the range of 60° C. to 200° C. for at least 2 minutes and not more than 90 minutes.
5. The method of claim 1 , wherein the additive material is present and the additive material comprises a blowing agent, and the foaming comprises decomposing the blowing agent to volatile components which foam the material upon release from the composition.
6. The method of claim 1 , wherein foaming the cross-linked intermediate composition to form the foamed article or material comprises the use of physical foaming with a supercritical fluid.
7. The method of claim 1 , wherein the blend composition is processed before cross-linking.
8. The method of claim 7 , wherein processing the blended composition comprises compression molding, injection molding, extrusion, or a combination thereof.
9. The method of claim 1 , wherein at least the portion of the exterior surface of the article or material is irradiated with low plasma discharge prior to the lamination of the film to the portion of the exterior surface of the foamed article or material.
10. The method of claim 1 , wherein the polyolefin comprises low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, one or more copolymers thereof, or a blend thereof.
11. The method of claim 10 , wherein the non-encapsulated paraffin wax comprises n-Octacosane, n-Heptacosane, n-Hexacosane, n-Pentacosane, n-Tetracosane, n-Tricosane, n-Docosane, n-Heneicosane, n-Eicosane, n-Nonadecane, n-Octadecane, n-Heptadecane, n-Hexadecane, n-Pentadecane, n-Tetradecane, n-Tridecane, or a combination thereof.
12. The method of claim 11 , wherein the weight:weight ratio of the non-encapsulated paraffin wax to the polyolefin is in the range of 1:10 to 2:1.
13. An article comprising:
a cross-linked polyolefin network,
a non-encapsulated paraffin wax having a lower weight average molecular weight than the weight average molecular weight of the polyolefin prior to cross-linking;
a porosity of 35% to 98% by volume; and
wherein the article is characterized by (i) a cross-linked portion in the range of 20 percent by weight to 35 percent by weight of the polyolefin; (ii) thermal conductivity in the range of 0.07 to 0.12 W/(m*K); and, (iii) wherein the article does not change more than 10% after 20 temperature cycles as measured by differential scanning calorimetry (DSC) wherein each temperature cycle encompasses the transition temperature of the phase change material of the foamed article or material and at least 10° C. on each side.
14. The article of claim 13 , wherein the polyolefin, prior to cross-linking, comprises low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, one or more copolymers thereof, or a blend thereof.
15. The article of claim 14 , wherein the non-encapsulated paraffin wax comprises n-Octacosane, n-Heptacosane, n-Hexacosane, n-Pentacosane, n-Tetracosane, n-Tricosane, n-Docosane, n-Heneicosane, n-Eicosane, n-Nonadecane, n-Octadecane, n-Heptadecane, n-Hexadecane, n-Pentadecane, n-Tetradecane, n-Tridecane, or a combination thereof.
16. The article of claim 15 , wherein the weight:weight ratio of the non-encapsulated paraffin to the polyolefin is in the range of 1:10 to 2:1.
17. The article of claim 13 , wherein the porosity of the article is between 50% and 85%.
18. The article of claim 13 , wherein the average pore size is in the range of 100 to 200 μm.