Phase change compositions

Abstract

Compositions containing crystalline, straight chain, alkyl hydrocarbons as phase change materials including cementitious compositions containing the alkyl hydrocarbons neat or in pellets or granules formed by incorporating the alkyl hydrocarbons in polymers or rubbers; and polymeric or elastomeric compositions containing alkyl hydrocarbons.

What is claimed is: 
     
       1. A composite useful in thermal energy storage comprising a matrix having incorporated therein a phase change material, said phase change material being a crystalline, .[.straight.]. .Iadd.long .Iaddend.chain, alkyl hydrocarbon having 14 or more carbon atoms and a heat of fusion greater than 30 cal/g., said composite also comprising a flame retarding agent selected from the group consisting of halogenated hydrocarbons and halogenated phosphates. 
     
     
       2. The composite of claim 1 wherein said matrix material is an inorganic cementitious material. 
     
     
       3. The composite of claim 2 wherein said inorganic cementitious material is selected from the group consisting of hydraulic .[.cements, gypsum, and concrete..]..Iadd.cements and gypsum..]..Iaddend. 
     
     
       4. The composite of claim 3 wherein said phase change material is incorporated into said matrix material in the form of a pellet. 
     
     
       5. The composite of claim 4 wherein said pellet comprises a matrix of a hard wax having a melting point greater than 50° C. and a penetration hardness less than 10 containing said phase change material. 
     
     
       6. The composite of claim 3 wherein said phase change material is pre-mixed with a highly absorptive filler before being introduced to said matrix material. 
     
     
       7. The composite of claim 1 wherein said flame retarding agent also includes a polyvalent metal oxide. 
     
     
       8. The composite of claim 2 wherein said composite is formed by infiltrating said matrix material with said phase change material in combination a wetting agent. 
     
     
       9. The composite of claim 8 wherein said wetting agent is stearic acid or stearyl alcohol. .[.10. The composite of claim 1 wherein said alkyl hydrocarbon is selected from the group consisting of Shellwax 100, Shellwax 120, Shellwax 200, Shellwax 300, Boron R-152, Union SR-143, Witco 128, Witco LLN, Witco 45A, Witco K-61, Witco K-51, Witco 85010-1, 
     
     
        Aristowax 143 and Paraffin 150..]. 11. The composite of claim 2 wherein said alkyl hydrocarbon is a blend of normal alkyl hydrocarbons containing 
     
     
        16 to 20 carbon atoms. 12. The composite of claim 1 wherein said halogenated hydrocarbon is selected from the group consisting of .[.Chlorowax 70-S,.]. tetrabromophthalic anhydride, tetrabromobisphenol A, and decarbomodiphenyl oxide; and said polyvalent metal oxide is antimony oxide, the weight ratio of said halogenated hydrocarbon to said antimony 
     
     
        oxide being about 1:1 to 3:1. 13. A composite of claim 1 wherein said 
     
     
        composite is a bridge deck. 14. A composite useful in thermal energy storage comprising a matrix material having incorporated therein a phase change material, said matrix material being plasterboard and said phase change material being a crystalline, .[.straight.]. .Iadd.long .Iaddend.chain, alkyl hydrocarbon having 14 or more carbon atoms and a heat of fusion greater than 30 cal/g., said plasterboard also comprising a flane retardant agent incorporated therein said flame retarding agent being selected from the group consisting halogenated hydrocarbons and 
     
     
        halogenated phosphates. 15. A composite useful in thermal energy storage comprising a matrix material having incorporated therein a phase change material and a flame retarding agent, said phase change material being a crystalline .[.straight.]. .Iadd.long .Iaddend.chain alkyl hydrocarbon having 14 or more carbon atoms and a heat of fusion greater than 30 cal/g and said flame retarding agent being a brominated hydrocarbon which is 
     
     
        miscible in said phase change material. 16. The composite of claim 15 wherein said brominated hydrocarbon is a brominated cycloalkylalkanes. 
     
     
            The composite of claim 16 wherein said brominated cycloalkylalkane is 
     
     
        dibromoethyldibromocyclohexane. 18. The composite of claim 1 wherein said flame retarding agent is a flame retarding agent selected from the group consisting of tri(beta-chloroisopropyl) phosphate and 
     
     
        tri(beta-chloroethyl)phosphate. .Iadd.19.  A method of thermal energy storage comprising providing a composite in thermally stable form and formed of a first material and a second material which is different from said first material, and which has a melting point less than said first material, but which is compatible with said first material, said first material comprising an inorganic cementitious matrix which serves as a containment means for said second material, said second material comprising a crystalline alkyl hydrocarbon material containing 14 or more carbon atoms or mixtures thereof and having a heat of fusion greater than about 30 cal/g, said second material being contained within the matrix of said first material, and subjecting said composite to changes in temperature whereby said composite either conserves heat or cool. 
     
     
        .Iaddend. .Iadd.20.  The method of claim 19 wherein said inorganic cementitious matrix comprises a cementitious material selected from the group consisting of hydraulic cements and gypsum. .Iaddend. .Iadd.21. The method of claim 20 wherein said inorganic cementitious matrix is in the form of a dry wall or a cured cement product. .Iaddend. .Iadd.22. The method of claim 21 wherein said composite is formed by infiltrating said inorganic cementitious matrix with neat crystalline alkyl hydrocarbon. .Iaddend. .Iadd.23. The method of claim 23 wherein said crystalline alkyl hydrocarbon is used in combination with a wetting agent. .Iaddend. .Iadd.24. The method of claim 20 wherein neat crystalline alkyl hydrocarbon is incorporated directly into said inorganic cementitious matrix by wet or dry mixing. .Iaddend. .Iadd.25. The method of claim 25 wherein said crystalline alkyl hydrocarbon is used in combination with a 
     
     
        wetting agent. .Iaddend. .Iadd.26.  The method of claim 19 wherein said phase change material comprises from 1 % to 20% by weight of said composition. .Iaddend.