A flexible thermal control composite comprising a natural or synthetic polymer and an endotherm dispersed, distributed and suspended within said natural or synthetic polymer i.e. "P"olymer "C"ontaining an "E"ndothermic "A"gent (PCEA). The PCEA can be formed into thin and thick films. It can be drawn, molded, extruded and spun into fibers or all dimensions. It can be formed and chopped into PCEA mulch. Irrespective its final form, the PCEA can be used in insulating, thermoprotecting, heat absorbing applications on the one hand, and heat maintenance applications of all types on the other.

SUMMARY OF THE INVENTION

The inventive composition of matter is a flexible thermal control composite. Said composite comprises a polymer and an endothermic agent. The endothermic agent is dispersed, distributed, and suspended in the polymer. Thereafter it is cured to form a "P"olymer "C"ontaining an "E"ndothermic "A"gent (PCEA) composite. This composite now has thermal control properties that make it suitable for a multitude of thermal control applications.

Natural or synthetic polymer may be softened or liquified by being (1) heated, (2) dissolved or (3) suspended in a plasticizer or solvent. When the polymer treated in any of these manners has an endothermic agent added to it, in very specific concentrations, distributed, dispersed, suspended therein and cured, a thermal control composite i.e. a PCEA is formed. Such PCEA is in essence capable of thermal control through its ability to absorb and store heat or through its ability to first absorb heat and then release it. It does so through the use of its endothermic compounds' own inherent thermodynamic, physical and chemical properties, i.e. their latent heats of fusion, hydration, formation, decomposition, vaporization, sublimation, or its allotropic and phase change reactions; while simultaneously completely eliminating any possibility of leakage of its endothermic compounds into the environment, as said agents become an integral part of the PCEA overall physical structure.

Thus, according to the present invention there is provided a PCEA thermal control composite comprising a natural or synthetic polymer and an endothermic agent. The PCEA thermal control composite can be thin, as for example a thin or a thick film, or molded as a thick PCEA brick. When the PCEA is a thin film, then the effective distribution of the endothermic agents within said polymer is 0.0001 to 1.2 gram of endothermic or thermal storage compound per square inch of PCEA, the PCEA having a thickness of 0.05 to 2.0 mil. On the other hand, where the PCEA is a thick film or molded structure, then the effective concentration of endotherm will be 0.05% 60% by weight endotherm in PCEA.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The inventive thermal control composite i.e. the PCEA material 10 of FIG. 1, FIG. 2, FIG. 3, and FIG. 4 (see Original Patent) shows the endothermic agent 11 dispersed, distributed and suspended within a polymer or plastic 12.

(a) The Polymer or Plastic.

The plastic or polymer 12 of the PCEA material 10 may comprise any natural or synthetic polymer or a mixture thereof. Such natural and synthetic polymers comprise: all latexes including those used in paint; fluoropolymers such as various TEFLON.RTM. species, specifically polytetrafluoroethylene (PTFE), polyfluoroacetate (PFA) and fluoroethylpropylene(FEP) and other fluorinated plastic films having similar thermal stability, i.e. FEP: -200 DEGREES C. TO 200 DEGREES C. and PFA: -200 DEGREES C. TO 250 DEGREES C., that are well known in the art; expanded TEFLON.RTM.; high temperature fluoroelastomers such as VITON.RTM. and other highly thermoresistant polymers and plastics well known in the art; elastomers such as SILICONE.RTM. species specifically polydimethylsiloxane and polymethylphenylsiloxane and other siloxanes well known in the art; polyimides such as KAPTON.RTM.; POLYESTERS.RTM. such as MYLAR.RTM.; high density polymers such as TIVAR.RTM. and SPECTRA.RTM.; and other polyamides, polyarylates, polyetherimides, polyketones, polyphenylene oxides or sulfides, polyphenylsulfones, polystilfones, acetals, nylons, ABS, polyetherketones, phenolics, polystyrenes, cellulose, polycarbonates, polyethylenes, polypropylenes, acrylics, polyurethanes, polyvinyls, polyvinylchlorides, BRICKLITE.RTM., polymeric and plastic materials well known to those skilled in the art of plastic materials. Preferably though the carrier plastic or polymer 13 should be TEFLON.RTM., SILICONE.RTM., or VITON.RTM..

These polymers can be photo, thermally or chemically cured. More importantly however, they have a molecular structure consisting of long chains of mostly linear molecules, which after being relaxed by either controlled heating, dissolution or suspension in a plisticizer or solvent, provide the interstitial spaces, through which the endothermic or thermal storage compounds weave and are distributed prior to curing and the final formation of the PCEA.

(b) The Endothermic Agent.

An endothermic compound or agent is by definition a compound that absorbs heat. The endothermic agents of the present invention can be strict endotherms, i.e. they absorb and retain heat without releasing it into the surrounding environment. Or they can be recyclable endotherms, such as phase change materials, where they absorb heat initially and then they release the heat, if they are subjected to an environmental temperature differential.

The endothermic agents of the present invention comprise the following: oxidized and unoxidized polymers; oxidized and unoxidized homopolymers of ethylene polymer compounds; carbon monoxide-bonded copolymers; micronized polyethylene waxes such as stearic acid; waxes derived from petroleum; ethylene-bis-stearamide; N,N-ethylene-bis-stearamide; various tars; high molecular weight oils and hydrocarbons; polyvinyl alcohols; oxidized and unoxidized polyethylene homopolymers; carnauba wax; aluminum hydroxide, calcium hydroxide, potassium hydroxide, lithium hydroxide and the mixtures thereof; boric acid; dodecaborane, paraldehyde, paraformaldehyde, trioxane and the mixtures thereof; lithium formate, lithium acetate, lithium carbonate, calcium carbonate, silicon carbonate, magnesium carbonate, sodium bicarbonate and the mixtures thereof; salts of acetic acid, salts of formic acid, salts of boric acid and the mixtures thereof; lithium chloride trihydrate, lithium nitrate trihydrate, sodium carbonate decahydrate, sodium borate decahydrate, hydrated epsom salts, magnesium nitrate hexahydrate, beryllium sulfate tetrahydrate, sodium phosphate dodecahydrate, calcium chloride hexahydrate, zinc sulfate heptahydrate, magnesium chloride hexahydrate, sodium sulfate decahydrate, aluminum oxide trihydrate, aluminum sulfate decaoctahydrate, aluminum fluoride trihydrate, and the mixtures thereof; and any eutectic mixtures of any of these materials or families of materials including salts with melting points below 550 degrees Celsius.

These endothermic agents may be micronized and added to the polymer(s) after said polymer(s) have been relaxed by either controlled heating, dissolution or suspension in a plasticizer or solvent. The endothermic agents are then subjected to a mixing process by which they are distributed through and suspended in the polymer(s)' interstitial spaces, or in the interstitial spaces of the outer surface of the polymer(s), and fixed therein through final curing steps which result in the inventive thermal control composite i.e. the PCEA.

The ultimate effective concentration of the endotherm in the PCEA is determined on a case by case application basis by such factors as: the particular application i.e. whether the application requires the absorption of heat or the release of heat, the needed heat capacity of the application, the type of polymer used, the particulate size of the endotherm, and the needed flexibility and use of the novel PCEA. Thus, when seeking a drapeable PCEA having a thickness of 0.3 to 1.0 mil for a heat absorbing/heat protective clothing application the carrier plastic or polymer may be a fluoroelastomer, and the concentration of the endothermic agent or thermal storage compound may range from 0.0001 to 1.2 grams of endotherm per square inch of PCEA; with a preferred concentration of 0.01 to 0.06 grams of endotherm per square inch of PCEA.

On the other hand, when seeking a flexible PCEA having an observable thickness of, for example 1 inch, then the carrier polymer may be a silicone and the effective concentration of the endotherm in the PCEA will be 0.05% 60% by weight endotherm in PCEA; with a preferred concentration of 20% by weight endotherm in PCEA, for extreme maximum flexibility relative to the highest heat capacity.

The heat absorption/heat protective and/or the heat release/heat preservation properties of the present inventive PCEA materials become readily apparent in the Test Examples below, which represent various embodiments of the inventive PCEAs.

(c) Embodiments of the Invention.

A series of different PCEAs were prepared in accordance with the principles and requirements as described above. Specifically, natural or synthetic polymers were selected from the group of polymers set forth above. These polymers in turn were softened or liquified by (i) heat, (ii) solution in a solvent or (iii) suspension in a plasticizer, using conventional methods of softening and liquification already known in the art of polymer handling and processing.

To these softened or liquified polymers, in turn, were added an endothermic or a recyclable endothermic agent, preferably micronized, selected from the group of endotherms or thermal storage compounds set forth above, in specific concentrations. The polymer and endotherm combinations were then mixed thoroughly to insure the distribution, dispersal, and suspension of the endotherms in the polymers's interstitial spaces; said spaces being formed during the softening of the polymers' long chains of mostly linear molecules. The mixtures were then molded and cured into PCEA thin and thick films, PCEA bricks, various shaped PCEA mulches or extruded, or extruded and spun into PCEA fibers. Alternatively, the PCEA mixtures were contacted, painted and cured onto a polymer substrate, so that upon cooling, or evaporation of the solvent or the plasticizer, the PCEA is literally adsorbed only on the surface of the underlying polymer substrate.
 

Claim 1 of 17 Claims

1. A cured flexible thermal control composite comprising boric acid distributed, dispersed and suspended in a polymer having a molecular structure consisting of long chains of mostly linear molecules which prior to curing provide interstitial spaces through which the boric acid is distributed, dispersed and suspended and defines a fixed state therein on curing; and a thermally conductive substrate adhered to said boric-acid containing polymeric material; wherein said boric acid functions as an endothermic agent to effect heat absorption at least in part based on liquefaction or decomposition of said boric acid in said fixed state.

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