# US 11,999,834 B2 · Precursor compositions for a protective article, protective articles comprising a reaction product of the precursor composition, related aerospace structures, and related methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,999,834 B2 - Document ID: US11999834B2 - Status: Granted - Kind: B2 - Application number: 16/446,038 - Filed: 2019-06-19 - Published: 2020-12-24 - Granted: 2024-06-04 - Earliest claimed: 2019-06-19 - Assignees: Northrop Grumman Systems Corporation - Applicants: Northrop Grumman Systems Corporation - Inventors: Cameron Hilton; Benjamin W. C. Garcia; Matthew Armentrout; Steven F. Stone; Christopher Deemer; Brian Barber - Web page: https://patentgrep.com/patent/US11999834B2 ## CPC - C08J 9/0085: {Use of fibrous compounding ingredients (C08J9/0076 takes precedence)} - C08J 9/32: from compositions containing microballoons, e.g. syntactic foams - B32B 5/18: characterised by features of a layer {of} foamed material - B32B 5/32: {at least two} layers being foamed {and next to each other} - B64C 7/00: Structures or fairings not otherwise provided for - C08J 9/0066: {Use of inorganic compounding ingredients} - C08J 9/0071: {Nanosized fillers, i.e. having at least one dimension below 100 nanometers} - C08J 9/228: Forming foamed products - B32B 2266/0207: Materials belonging to B32B25/00 - B32B 2605/18: Aircraft - C08J 2201/026: Crosslinking before of after foaming - C08J 2203/22: Expandable microspheres, e.g. Expancel® - C08J 2333/06: of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical - C08J 2333/08: Homopolymers or copolymers of acrylic acid esters - C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29) - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM - B64C: AEROPLANES; HELICOPTERS ## Abstract A precursor composition comprising, before cure, an acrylic ethylene monomer (AEM), a foaming agent, and one or more of a strengthening additive, a thermal ablation additive, or a reflectivity additive. The precursor composition is cured to form a protective article comprising a foamed protective material. A method of forming a protective article is also disclosed, as is an aerospace structure comprising the foamed protective material. ## Claims ### Claim 1 A precursor composition comprising, before cure: a primary polymer in an amount of from about 65.0% by weight to about 80.0% by weight based on a total weight of the precursor composition, wherein the primary polymer is an acrylic ethylene monomer (AEM); a foaming agent comprising expandable microspheres; a strengthening additive in an amount of from about 2% by weight to about 20% by weight based on the total weight of the precursor composition, wherein the strengthening additive comprises one or more of chopped polyaramid fibers, nanotubes, platelets, rods, or disks of one or more of carbon, glass, metal, or ceramic; a peroxide curing agent and a peroxide cure accelerator, and one or more additional additives comprising a thermal ablation additive, an x-ray absorption additive, or a reflectivity additive, wherein the precursor composition is free of an amine curing agent. ### Claim 2 (depends on 1) The precursor composition of claim 1, wherein the expandable microspheres are in an unexpanded form. ### Claim 3 (depends on 1) The precursor composition of claim 1, wherein the acrylic ethylene monomer comprises a terpolymer of ethylene, an alkyl acrylate, and an acidic cure site monomer. ### Claim 4 (depends on 1) The precursor composition of claim 1, wherein the peroxide cure accelerator comprises N,N′-m-phenylenedimaleimide. ### Claim 5 (depends on 1) The precursor composition of claim 1, wherein the foaming agent is present in an amount of from about 2% by weight to about 20% by weight based on the total weight of the precursor composition. ### Claim 6 (depends on 1) The precursor composition of claim 1, wherein the strengthening additive comprises the chopped polyaramid fibers. ### Claim 7 (depends on 1) The precursor composition of claim 1, wherein the one or more of nanotubes, platelets, rods, or disks, of one or more of carbon, glass, metal, or ceramic comprise one or more of carbon nanotubes, graphene, carbon black, fumed silica, or precipitated silica. ### Claim 8 (depends on 1) The precursor composition of claim 1, wherein the reflectivity additive comprises boron nitride, titanium oxide, or combinations thereof. ### Claim 9 (depends on 1) The precursor composition of claim 1, wherein the strengthening additive is present in an amount of from about 6.0% by weight to about 16.0% by weight based on the total weight of the precursor composition. ### Claim 10 (depends on 1) The precursor composition of claim 1, wherein the precursor composition comprises the AEM, the expandable microspheres, the chopped polyaramid fibers, precipitated silica, 4-(1-methyl-1-phenylethyl)N-[4-(1-methyl-1-phenylethyl)phenyl] aniline, polyoxyethylene octadecyl, and one or more fatty acid phosphate derivatives. ### Claim 11 (depends on 1) The precursor composition of claim 1, wherein the strengthening additive further comprises chopped fibers of one or more of carbon, aramid, glass, metal, quartz, or ceramic. ### Claim 12 (depends on 1) The precursor composition of claim 1, wherein the foaming agent is present in an amount of from about 2.8% by weight to about 7.4% by weight based on the total weight of the precursor composition. ### Claim 13 A protective article, comprising: a foamed protective material comprising a reaction product of a precursor composition comprising: a primary polymer in an amount of from about 65.0% by weight to about 80.0% by weight based on a total weight of the precursor composition, wherein the primary polymer is an acrylic ethylene monomer (AEM); expanded microspheres; a strengthening additive in an amount of from about 2% by weight to about 20% by weight based on the total weight of the precursor composition, wherein the strengthening additive comprises one or more of nanotubes, platelets, rods, or disks of one or more of carbon, glass, metal, or ceramic; a peroxide curing agent and a peroxide cure accelerator; and one or more additional additives comprising a thermal ablation additive, a reflectivity additive, or an x-ray absorption additive; wherein the precursor composition is free of an amine curing agent; and wherein the foamed protective material exhibits a density of from about 0.1 g/ml to about 1.0 g/ml. ### Claim 14 (depends on 13) The protective article of claim 13, wherein the reaction product comprises a crosslinked AEM material surrounding the expanded microspheres. ### Claim 15 (depends on 14) The protective article of claim 14, wherein the foamed protective material comprises substantially uniformly distributed cells. ### Claim 16 (depends on 13) The protective article of claim 13, wherein the foamed protective material exhibits a density of from about 0.1 g/ml to about 0.5 g/ml. ### Claim 17 (depends on 13) The protective article of claim 13, wherein the foamed protective material exhibits a density of from about 0.5 g/ml to about 1.0 g/ml. ### Claim 18 (depends on 13) The protective article of claim 13, further comprising one or more materials adjacent the foamed protective material. ### Claim 19 An aerospace structure comprising: a protective article on at least a portion of an external surface of an aerospace structure, the protective article comprising a foamed protective material comprising a reaction product of a precursor composition comprising: a primary polymer in an amount of from about 65.0% by weight to about 80.0% by weight based on a total weight of the precursor composition, wherein the primary polymer is an acrylic ethylene monomer (AEM); expandable microspheres; a strengthening additive in an amount of from about 2% by weight to about 20% by weight based on the total weight of the precursor composition, wherein the strengthening additive comprises one or more of nanotubes, platelets, rods, or disks of one or more of carbon, glass, metal, or ceramic; a peroxide curing agent and a peroxide cure accelerator; and one or more additional additives comprising a thermal ablation additive, a reflectivity additive, or an x-ray absorption additive; and wherein the precursor composition is free of an amine curing agent. ### Claim 20 (depends on 19) The aerospace structure of claim 19, wherein the protective article comprises a single layer of the foamed protective material. ### Claim 21 (depends on 19) The aerospace structure of claim 19, wherein the protective article comprises a multilayer protective article. ### Claim 22 A method of forming a protective article, comprising: forming a precursor composition comprising: a primary polymer in an amount of from about 65.0% by weight to about 80.0% by weight based on a total weight of the precursor composition, wherein the primary polymer is an acrylic ethylene monomer (AEM); a foaming agent comprising expandable microspheres; a strengthening additive in an amount of from about 2% by weight to about 20% by weight based on the total weight of the precursor composition, wherein the strengthening additive comprises one or more of nanotubes, platelets, rods, or disks of one or more of carbon, glass, metal, or ceramic; a peroxide curing agent and a peroxide cure accelerator; and one or more additional additives comprising a thermal ablation additive, a reflectivity additive, or an x-ray absorption additive; wherein the precursor composition is free of an amine curing agent; and exposing the precursor composition to heat to form a foamed protective article. ### Claim 23 (depends on 22) The method of claim 22, wherein exposing the precursor composition to heat comprises substantially simultaneously crosslinking the AEM and foaming the precursor composition. ### Claim 24 (depends on 22) The method of claim 22, wherein exposing the precursor composition to heat comprises foaming the precursor composition and subsequently crosslinking the precursor composition. ### Claim 25 (depends on 22) The method of claim 22, wherein exposing the precursor composition to heat comprises exposing the precursor composition to a temperature between about 121° C. and about 232° C. ### Claim 26 (depends on 22) The method of claim 22, wherein exposing the precursor composition to heat comprises exposing the precursor composition to a first temperature to foam the precursor composition and exposing the precursor composition to a second temperature to crosslink the precursor composition.