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.