U.S. Army Research, Development and Engineering Command

ASETSDefense 2012: Sustainable Surface Engineering for Aerospace and Defense

August 28th, 2012

John A. Escarsega, Dawn M. Crawford & Fred Lafferman

The Validation and

Approval of Chemical Agent Resistant

Coatings

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4. TITLE AND SUBTITLE The Validation and Approval of Chemical Agent Resistant Coatings

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13. SUPPLEMENTARY NOTES ASETSDefense 2012: Sustainable Surface Engineering for Aerospace and Defense Workshop, August27-30, 2012, San Diego, CA. Sponsored by SERDP/ESTCP.

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Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18

•Who We Are & What we Do

•Standardization & Specifications

•Technical Challenges

•Selected CARC Efforts and discussions

•Final Thoughts

Outline

• ARL is the Lead DOD R&D Activity for CARC Innovative formulations approaches New raw materials selections Advanced characterization

• Maintains Ownership for all key specifications regarding pretreatments, primers and topcoats for all tactical and related support equipment and munition coatings. Elements above assist to implement and transition products to the field.

Who We Are …

What we do…

• Develop materials for military unique coatings including pretreatments, primers, and topcoats – Chemical Agent Resistant Coatings – Munitions coatings – Industrial coatings for vehicle interiors

• Implement and transition new products – Specifications and Standards – Troubleshooting, consulting, and problem solving

• Analyze and solve technical problems related to coatings systems used on Army Materiel

Guiding Principles for Coating Systems

Survivability Environmental

Durability

Implementation

Standardization

• Every item that the Army fields starts with a document, namely a specification. Multiple specifications may be required to define a specific item along with a standard on how to process the item. Cleaning Methods Pretreatment Methods Anticorrosive Primers Chemical Agent Resistant Coating (CARC) Topcoat Governed by application and inspection specification, MIL-DTL-53072.

Standardization Document Development Process

• Step 1 – Planning • Step 2 – Research & Development • Step 3 – Approval and Publication

• Reasons for development or revision of specifications:

Environmental regulations (Hexavalent Chromate and HAPs) Performance requirements Advances in new technology Major gaps in technology

• Uniqueness of Coating and Corrosion Team Specifications:

Notarized Statements of Composition

• Transition document for military to use in contracts

CARC epoxy primer (0.8 - 1.2 mils)

Substrate (ferrous or nonferrous)

CARC Camouflage

Polyurethane Topcoat (1.8 mil)

Chemical Conversion Coating (0.2-0.3 mil)

Today

Tailored CARC Coating

Advanced Corrosion Protection Layer

Tomorrow

•Ferrous •Nonferrous •Polymer Composite

Substrate

•Corrosion Protection •Texture

Functional Primer

•Functional pigmentation •Controlled Roughness

CARC is a System

•Visible and NIR •Silica extender •Semitransparent binders

Hierarchical Architecture of Multifunctional Coatings

Raw Material Selection and Design

Resin

Pigment(s)

Extenders

Additives

Individual Coating Components

Solvents

Pigments & Extenders: 50%

V-12650 Cobalt Free

Extenders High density Polyethylene

Resin: Part A 60% solids

Part B: 100% solids reduced with TBA 25%

48%

Solvents : Water & Tert Butyl Acetate

Additives

2%

Key Technical Challenges

• Hexavalent Chromium Free Pretreatments for various substrates.*

• Alternatives to Isocyanate Based Topcoats*

• Elimination of Silica Flattened topcoats

• New Chemical Agent Testing Methodologies

• Alternatives to conventional cure

Pigments/Extenders

• Polymeric beads – Reduce chalking

effect – Improve UV

resistance – Improve

performance

Polymeric beads

Army will Discontinue use of Silica based

topcoats

Diatomaceous silica Talc

•Integrated within Film

Silica vs. Polymeric Accelerated Outdoor Weathering Results

0MJ/m2

70MJ/m

2

140MJ/m2

210MJ/m2

280MJ/m2

350MJ/m2

420MJ/m2

490MJ/m2

560MJ/m2

630MJ/m2

700MJ/m2

770MJ/m2

840MJ/m2

910MJ/m2

980MJ/m2

1050MJ/m2

1120MJ/m2

1190MJ/m2

1260MJ/m2

1400MJ/m2

64159 Type I Silica 0.00 0.49 0.88 1.01 0.92 0.80 0.75 0.77 1.22 1.02 1.82 1.82 2.81 3.52 3.90 4.26 4.52 5.16 5.55 5.45

64159 Type II Polymeric 0.00 0.92 1.22 1.33 1.36 1.39 1.25 1.27 1.11 0.94 1.10 1.07 1.39 1.51 1.49 1.59 1.57 1.46 1.56 1.44

53039 Type I Silica 0.00 0.34 0.45 0.51 0.48 0.75 1.26 1.49 2.62 2.98 5.02 4.83 5.79 6.46 6.70 7.22 7.24 7.37 7.47 7.80

53039 Type IV Polymeric 0.00 0.28 0.53 0.61 0.65 0.78 0.86 0.85 0.82 0.65 0.54 0.60 0.53 0.71 1.01 1.65 2.28 3.04 3.45 3.59

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

Delta

E*

Q-Lab Arizona, Accelerated Outdoor Weathering Results

Benefits of Polymeric Formulations vs. Silica Formulations

• Superior weather resistance—Minimal chalking and color degradation.

• Survivability—Spectral and specular reflection not affected by weathering. Infrared not affected during weathering.

• Superior mar resistance. • Less paint weight- 20-25% • Less paint usage—Documented by Star4D and Sikorsky

Helicopter—10-15%. Confirmed by industry and depots. • Health and safety—No crystalline silica exposure during

repair, sanding and removal operations. • Longer service life—less cost for repainting.

ARL Approach and Considerations

Raw Material Selection

Surface Enhanced

In situ Cross-Linked

Two Fold Approach : Incorporating

chemistries to actively bind and crosslink to

create barrier properties and support

decontamination through additional

surface modifications

Providing Agent Resistance Resin

Tailored Coating

Polymeric Flattening Agents

Additives

Pigments

Solvents

Why UV Cure?

• OEM’s and Depot’s define production delays as a critical gap

• UV cure chemistry enables handling in 10 minutes vs. 6-8 hours (standard cure)

• Reduce VOC’s • Highly adaptable and

relevant for field repairs Reduce Dry to Fly Time

Polyurethane/Acrylate Interpentrating Polymer Network

UV Cure

10 min.

Time

24 hours

Acrylate network

Set to handle

IPN of urethane/urea/ allophonate and acrylate networks

Field Ready

Co-blend

UV initiated resin

Hydroxyl functional polyurethane resin

Rapid UV Cure WD CARC 2K Water Dispersible Paint with

UV active additives

3. 10 minute cure process using H & S Auto Shot 1200W UVA lamp

1. Mix and spray the same as MIL-DTL-64159

2. Allow 10 minute of flash off for evaporation

Rapid UV Cure WD CARC

UH-60 rotor blade section coated with black rapid cure CARC. Cured with two 1200W UVA lamps in tandem.

Accomplishments

• Patent Application Filed • Formulations completed for green and black

using low solar absorbing (LSA) pigmentation • Optimized UV irradiance requirements for rapid

cure (8 inch stand-off distance/ 10 minutes of UVA light exposure). Panel results show “set to handle” properties after 10 minutes following UV cure, dry hard property after 30 minutes following UV cure and MEK resistance in less than 24 hours.

• Demonstrated success of UV cure CARC on small section of UH-60 and CH-47 rotor blades.

Closing Thoughts

• Technology Gaps/Accomplishments are continually evolving.

• Our successes will be with the continued collaborations with our services, industry and academia.

• Our specification and technical manuals will define the requirements and processes.

• It is within this framework that the path will be most clear and straight forward.