# US 2020/0399436 A1 · Precursor compositions for a protective article, protective articles comprising a reaction product of the precursor composition, related aerospace structures, and related methods

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- Number: US 2020/0399436 A1
- Document ID: US20200399436A1
- Status: Published application
- Kind: A1
- Application number: 16/446,038
- Filed: 2019-06-19
- Published: 2020-12-24
- Earliest claimed: 2019-06-19
- Assignees: Northrop Grumman Innovation Systems, Inc.
- Applicants: Northrop Grumman Innovation Systems, Inc.
- Inventors: Cameron Hilton; Benjamin W.C. Garcia; Matthew Armentrout; Steven F. Stone; Christopher Deemer
- Web page: https://patentgrep.com/patent/US20200399436A1

## 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:
an acrylic ethylene monomer, a foaming agent, and one or more of a strengthening additive, a thermal ablation additive, an x-ray absorption additive, or a reflectivity additive.

### Claim 2 (depends on 1)

The precursor composition of claim 1, wherein the foaming agent comprises expandable microspheres.

### Claim 3 (depends on 2)

The precursor composition of claim 2, wherein the expandable microspheres are in an unexpanded form.

### Claim 4 (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 5 (depends on 1)

The precursor composition of claim 1, wherein the acrylic ethylene monomer comprises from about 50.0% by weight (wt %) to about 80.0 wt % of a total weight of the precursor composition.

### Claim 6 (depends on 1)

The precursor composition of claim 1, wherein the foaming agent comprises from about 2.0 wt % to about 20 wt % of a total weight of the precursor composition.

### Claim 7 (depends on 1)

The precursor composition of claim 1, wherein the one or more of a strengthening additive, a thermal ablation additive, or a reflectivity additive comprises fibers of carbon, aramid, glass, metal, quartz, ceramic, or combinations thereof.

### Claim 8 (depends on 1)

The precursor composition of claim 1, wherein the one or more of a strengthening additive, a thermal ablation additive, or a reflectivity additive comprises nanotubes, platelets, rods, disks, or combinations thereof of carbon, glass, metal, ceramic, or combinations thereof.

### Claim 9 (depends on 8)

The precursor composition of claim 8, wherein the nanotubes, platelets, rods, disks, or combinations thereof of carbon, glass, metal, ceramic, or combinations thereof comprise carbon nanotubes, graphene, carbon black, fumed silica, precipitated silica, or combinations thereof.

### Claim 10 (depends on 1)

The precursor composition of claim 1, wherein the one or more of a strengthening additive, a thermal ablation additive, or a reflectivity additive comprises boron nitride, titanium oxide, or combinations thereof.

### Claim 11 (depends on 1)

The precursor composition of claim 1, wherein the one or more of a strengthening additive, a thermal ablation additive, or a reflectivity additive comprises from about 0.5 wt % to about 50.0 wt % of a total weight of the precursor composition.

### Claim 12 (depends on 1)

The precursor composition of claim 1, wherein the precursor composition comprises the AEM, expandable microspheres, 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 13

A protective article, comprising:
a foamed protective material comprising a reaction product of an acrylic ethylene monomer (AEM), expanded microspheres, and one or more of a strengthening additive, a thermal ablation additive, or an absorption additive, 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

A method of forming a protective article, comprising:
forming a precursor composition comprising an acrylic ethylene monomer (AEM), a foaming agent comprising expandable microspheres, and one or more additives; and
exposing the precursor composition to heat to form a foamed protective article.

### Claim 20 (depends on 19)

The method of claim 19, wherein exposing the precursor composition to heat comprises substantially simultaneously crosslinking the AEM and foaming the precursor composition.

### Claim 21 (depends on 19)

The method of claim 19, wherein exposing the precursor composition to heat comprises foaming the precursor composition and subsequently crosslinking the precursor composition.

### Claim 22 (depends on 19)

The method of claim 19, wherein exposing the precursor composition to heat comprises exposing the precursor composition to a temperature between about 121° C. and about 232° C.

### Claim 23 (depends on 19)

The method of claim 19, 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.

### Claim 24

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 an acrylic ethylene monomer (AEM), expanded microspheres, and one or more additives.

### Claim 25 (depends on 24)

The aerospace structure of claim 24, wherein the protective article comprises a single layer of the foamed protective material.

### Claim 26 (depends on 24)

The aerospace structure of claim 24, wherein the protective article comprises a multilayer protective article.