Demonstration of Military Composites with Low Hazardous Air Pollutant Content Dr. John J. LaScalla U.S. Army Research Laboratory Presented at a meeting of the Thermoset Resin Formulators Association at the Hyatt Regency Savannah in Savannah, Georgia, September 10 – 11, 2007 This paper is presented by invitation of TRFA. It is publicly distributed upon request by the TRFA to assist in the communication of information and viewpoints relevant to the thermoset industry. The paper and its contents have not been reviewed or evaluated by the TRFA and should not be construed as having been adopted or endorsed by the TRFA.
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Demonstration of Military Composites with Low Hazardous Air Pollutant Content
Dr. John J. LaScallaU.S. Army Research Laboratory
Presented at a meeting of the Thermoset Resin Formulators Association at the Hyatt Regency Savannah in Savannah,
Georgia, September 10 – 11, 2007
This paper is presented by invitation of TRFA. It is publicly distributed upon request by the TRFA to assist in the communication of information and
viewpoints relevant to the thermoset industry. The paper and its contents have not been reviewed or evaluated by the TRFA and should not be construed as
having been adopted or endorsed by the TRFA.
Demonstration of Military Composites with Low Hazardous
Air Pollutant Contents
John J. La Scala, Ph.D.U.S. Army Research Laboratory
Materials Application BranchAPG, MD 21005-5069
HMMWV ballistic hardtopHMMWV transmission
container
HMMWV hood
M35A3 hood
T-38 dorsal cover MCM composite rudder
Demonstrations
Outline
• Reducing Hazardous Air Pollutant (HAP) emissions from composite resins
• Demonstration Platforms
• Validation of Resin Production and Neat Resin Properties
• Validation of Composite Properties
UPE and VE Resins
+
Styrene
OHOH O R O O R O O R O
O O O O O O O O
n
Unsaturated Polyester
Vinyl Ester
Thermosetting Polymer
Initiator + Heat
O
O
O
OH
CH3
CH3
O O
OH
CH3
CH3
O O
O
OH
n
HAP Emissions
VOC/HAP Emissions
• Liquid resins used in molding large-scale composites are a significant source of Hazardous Air Pollutants (HAP)
Curing and Post-curing
HAP evolution
HAP evolution HAP
evolution
HAP evolution
Mixing Molding In Service
Composites industry consumes 9% of the styrene, but accounts for 79% of styrene emissions
• EPA - Reinforced Plastic Composites National Emissions Standards for Hazardous Air Pollutants (NESHAP)– Executed and legally enforceable as of April 28, 2003 – new sources– Executed and legally enforceable as of April 28, 2008 – existing sources
Fatty Acid Based Monomers
(MFA)Methacrylated
Fatty Acid
Route 4
O
O
Structure 4
O
OO
O
O OStructure 0
Route 3
O
O
OH
O
O
O
O
OH
Structure 3b
O
O
OH
O
OH
Structure 3a
Route 6
O
OO
O CH3
OH
Structure 6b
O
O CH3
Structure 6a
Route 2
O
O
O
OCH3
OH
Structure 2b
O
OCH3
Structure 2a
Route 1OH
OStructure 1a
Structure 1bR
O
O
O
O R
Route 5
Structure 5Route 7
O
O
OH
O
O
Structure 7b
O
OH
Structure 7aRoute 8
O
OO
OHOH
Structure 8a
O
OO
OOH
O
O
OH
Structure 8b
* Source: ARL/Drexel patent application, April 2005.
Plant oils e.g. soybean oil
Fatty Acid Vinyl Ester Resins (FAVE)
• VE– Bisphenol A– Novolac
• MFA – Non-volatile and inexpensive– Copolymerizes with styrene and vinyl ester– Soluble in VE and UPE– Increases renewable content in polymers– Reduces VOC/HAP emissions by 55-78%
+
O
O
O
OH
CH3
CH3
O O
OH
CH3
CH3
O O
O
OH
n
Vinyl Ester
Styrene MFA – methacrylated fatty acid
O
O
OH
O
OCommercial Resins
Low VOC ~ 33 wt% Sty
Standard ~ 40-50 wt% Sty
10-25 wt%
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60Time (hrs)
Nor
mal
ized
Mas
s Lo
ss (g
/g)
FAVE (20% styrene)
standard VE (45% styrene)
Low Volatile Contents
• MFA monomers themselves produce no emissions
Low VOC
Commercial resin Macro TGA
• Low VOC resin systems reduce emissions by 33-78%
Outline
• Reducing HAP emissions from composite resins
• Demonstration Platforms
• Validation of Resin Production and Neat Resin Properties
• Validation of Composite Properties
HMMWV ballistic hardtopHMMWV transmission
container
HMMWV hood
M35A3 hood
T-38 dorsal cover MCM composite rudder
Demonstrations
Marines Demo: Amtech Ballistic Helmet Hardtop®
• Need for added ballistic protection and closed molding process
• New Ballistic Hardtop– 3-Tex materials (54
oz) used– Toughened
Derakane 8084 vinyl ester resin (~40% styrene)
Demonstrate/Validate low VOC/HAP formulations for
HMMWV hardtop
• Testing of demo– Meets demanding structural
requirements– Exceeds all ballistic
requirements– 3000 mile off-road durability
Army Demo: Tactical Vehicle Replacement Parts
• Corrosion issues with M35A3• Sheet molding compound
(SMC) HMMWV hood has poor performance
• Transmissions damaged in shipment without good packaging
• Test demo parts– Flexural, impact, cyclic load,
High T, etc.
Air Force Demo: T-38 Dorsal Cover
• 400 planes upgraded to ‘C’ model• Upgrade caused pre-mature failure• AFRL developed new VARTM
Demonstrate/Validate low VOC/HAP formulations for one of
these applications
DISBONDEDGEDELAMINATION
DISBONDEDGEDELAMINATION
Navy Demo: Rudders for MCM, DDG, and DDX
• Straight rudder (MCM)
• Composite twisted rudder (CTR) – DDG and DDX
• Easier to fabricate and less cavitation than steel twisted rudders
• Composite rudder on MCM-9 has good success after 6 year fielding trial
Demonstrate/Validate low VOC/HAP formulations for one of these applications
Benefit to the Soldier/DoD
• Lowers health risk to workers
• Enable composite resins to meet EPA regulations
• Allows continued use of VE/UPE resins for the fabrication of current and future composites for the military– Lighter, faster, and more maneuvarable– Less maintenance – less corrosion, higher durability– Improved design
Resin Replacements for Specific Military Applications
• To determine the amount of unreacted acid in the resin • Acid number is mass of NaOH required to neutralize 1g of a
substance– 1 gram of the resin was dissolved in 5 grams of acetone– Indicator: 2 drops of 0.5 wt% phenolphthalein in 50% ethanol– Titrated with 0.5 N sodium hydroxide – Endpoint: when the solution remained pink for 30 seconds
Material Acid Number Max ValueMLau 17.5 20MOct 16.0 20
Army Research Labs, AMSRD-ARL-WM-MC, Bldg. 4600,Aberdeen Proving Grounds, MD 21005
Backup Slides
Neat Resin Properties
• BM-VE resins have low VOC and good toughness• FA-VE resins have ultra low VOC and high toughness,
but have lower strength and modulus
Property FA-VE Resin
BM-VE Resin
Low VOC Commercial
Resins
Standard Commercial
Resins Styrene Content (wt%) 10-20 28-38 33 45 Tg (ºC) 120-130 130-140 140 125 Flexural Strength (MPa) 120 130 130 130 Flexural Modulus (GPa) 3.0 3.5 3.5 3.4 Toughness (J/m2) 200 200-300 110 240 Viscosity at 30ºC (cP) 100-400 150-400 312 270 Gel times 5 min-7 hrs Not tested Various Various Shrinkage Low Moderate Moderate High Renewable Partly No No No Biodegradable No No No No Cost ~$4/lb (low
size-scale) >$2.24/lb ~$2.24/lb ~$2.15/lb
Derakane 441-400
Derakane 411-350
NESHAPSmall Businesses (< 100 tpy HAP)
• Bimodal blends meet most NESHAPs• Fatty acid-based resins exceed all NESHAPs
Including gel coats
0
10
20
30
40
50
60
vacuum mechanical manual
Operation
Max
imum
HA
P C
onte
nt (w
t%)
High Strengthnon-HSgel - whitegel - pigmentedgel - HSgel - clear
FA-VE
BM-VEDerakane 441-400
- Poor performanceDerakane411-C50
- Does not meet standards for manual ops.
- Barely meets other standards
NESHAPLarge Businesses (> 100 tpy HAP)
• Fatty acid-based resins meets standards for clear and HS gel coats• Fatty acid-based resins are close to meeting other NESHAPs
– Combination of styrene suppressants and bimodal blends– Add-on control devices
0
2
4
6
8
10
12
14
vacuum mechanical manual
Operation
Max
imum
HA
P C
onte
nt (w
t%)
High Strengthnon-HSgel - whitegel - pigmentedgel - HSgel - clear
FA-VE
Derakane resins do not come close to meeting these
standards
Acknowledgements
• Army Research Labs– J.M. Sands, R.E. Jensen, L.J. Holmes, W. Ziegler, J. Beatty, J.
Escarsega, P. Smith, S. H. McKnight, M. Maher
• Drexel University– Palmese research group
• CCM, University of Delaware– N. Shevchenko, S. Anderson, M. Logan, Wool Research Group
Low VOC Resin TechnologyLow Cost and High-Impact Environmental Solutions for Composite Structures
VOC evolution
VOC evolution VOC
evolution
VOC evolution
Mixing Molding Curing and Post-curing In Service
VOC evolution
VOC evolution VOC
evolution
VOC evolution
Mixing Molding Curing and Post-curing In Service
Applications
Facilities
Liquid resins used in molding large-scale composites are a significant source of Volatile Organic Compound (VOC) emissions. In fact, the composites industry only consumes 9% of the styrene, but produces 79% of the emissions. For this reason, the EPA has enacted the Reinforced Plastic Composites NESHAP, which mandates the maximum HAP content in liquid molding resins.
Army Research Laboratory Rodman Materials Building APG, MD
Drexel University Philadelphia, PA
• Military vehicles and structure• Automobile parts• Boats• Gel coats
Need for Low VOC Resins Solutions• Fatty acid monomers as styrene
replacements• Tailor molecular structure of vinyl
ester monomers
Applicable to all uses of unsaturated polyesters and vinyl esters, including all methods of manufacture.
Soybeans
Resin Processing– Low viscosity– VARTM, SCRIMP,
SMC capabilities
Polymer Properties– High Tg, strength,
toughness– Comparable to
commercial resins
O
O
O
OH
CH3
CH3
O O
OH
CH3
CH3
O O
O
OH
n
VOC
Low VOC Resin
To discuss licensing this technology, contact: Professor Giuseppe R. Palmese, Drexel University, Department of Chemical Engineering, Philadelphia, PA 19104, 215-895-5814, [email protected]