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Modern PTFE membrane based HEPA/ULPA filters for improved energy savings and risk reduction
Marc Schmidt, Ph.D.AAF International
Heppenheim (Germany)[email protected]
+49 175 18 788 78
Belgian Cleanroom Workgroup (BCW) – Cleanroom College Day 2019Ghent (Belgium)
Mar 21, 2019
Who We Are
• AAF Founded 1921
• World’s Leading Air Conditioning and Air
Filtration Company
• 2016 sales ≈ $20B in over 150 countries
• > 67.000 employees
HVAC Systems Air Filtration Chemicals
• 245 Subsidiaries• 218 International• 27 in Japan
Glass Fiber Media
First developed in the 1940’s.
Glass fiber in use 75+ Years.
Slurry of glass fibers in water with binder.
Poured on a moving screen conveyor.
Water vacuumed from below.
Baked dry in an oven.
Pleated into packs.
Potted in urethane in filter frames.
Industry ‘standard’ for high efficiency filtration due to it’s fine fiber diameter.
Media is extremely fragile!
Media is delicate and vulnerable at every stage of manufacturing, filter installation and testing!
Discovery
• Dr. Roy Plunkett (1910-1994) accidently discovered PTFE on April 6, 1938 at company DuPont.
• He had been looking for better coolant agent.
• Leaving a batch of tetrafluoroethylene (TFE) gas in a pressure container overnight, he found the next day a layer of a white translucent waxy solid, polymerized TFE: Polytetrafluoroethylene (PTFE)!
• Polytetrafluoroethylene was abbreviated to Teflon as registered as trademark in 1945.
source: www.worldofchemicals.com
Structure
• Fluorine saturated carbon chain (C2F4)n.
• Long chains with high molecular weight.
• Strong fluoro-carbon bonding.
• Fluorine atoms surround central ethylene carbon chain completlyprotecting it.
• Hydrophobic.source: http://www.bobbyrahalacura.com/tst.htm
PTFE - Polytetrafluoroethylene
e-PTFE HEPA filter membrane 1988 Daikin discovered ultrafine fiber structure.
e-PTFE approx. 30 years.
Semicon application adoption late 1990’s.
Starts with ‘fine powder’, mixing, pre-forming, extruding paste.
Stretching, drying, calandering.
Stretching-Scoring, laminating, pleating.
Single layer of expanded PTFE supported by a layer of spun bonded synthetic media on the upstream and downstream side.
Available in H13 – U17.
Standard for Microelectronic and Tool Market.
Compatible with Discrete Particle Counters (DPC) testing.
Media is VERY robust!
Whole process controlled in a cleanroom environment.
Nonwoven
Support Layer
Human Hair(for comparision)
PTFE
Nodes(for structure)
PTFE
Fibrils(for filtration)
⦰ ≈ 60µm
ePTFE membrane media(≈100μm depth,
i.e. 1.000x diameter of
0,1µm particle
→
deep filtration!)
ePTFE HEPA filter membrane
e-PTFE membrane structure and cross-section SEM e-PTFE is a 3 layer composite with 2 layers of
PE/PET (Polyethylene/Polyethyleneterephthalate) Scrim on both air entering side and air leaving side. The composite media is uni-directional.
ePTFE
composite
PE/PET
Scrim
ePTFE membrane
PE/PET Scrim
ePTFE
membrane
≈ 0,03 - 0,3 mg/m3
≈ 5 - 40 mg/m3
0,01
0,1
1
10
100
DPC Photometer
ae
ros
ol c
on
ce
ntr
ati
on
mg
/m3
µg/l = mg/m3
Aerosol challenge concentration
e-FRM Membrane Media
Optimized design of membrane layer supported by a layer of spun bonded synthetic media on the upstream and downstream side.
Available in H13 – H14.
High DHC on Oil Based aerosols.
Compatible with photometric test methods.
MPPS – microglass vs. eFRM media
- MPPS = Most Penetrating Particle Size
- Comparative MPPS graphs are based on efficiency tests
with flat media sheets @ airflow of 5.3 cm/s
ePTFE ULPA
eFRM HEPA
microglass
Proven Durability— 84x the pleated strength of microglass
VERY
FRAGILE
Chemical resistance results
*PTFE membrane intact but support layer affected
solvent (dipped in for 24h) efficiency pressure drop weight
water pure water ✔ ✔ ✔
acid
conc. hydrochloric acid (35%) ✔ ✔ ✔
conc. sulphuric acid (95%) ✔ ✔ reduced*
conc. nitric acid (60%) ✔ ✔ ✔
conc. hydrofluoric acid (47%) ✔ ✔ ✔
alkalisammonia solution (28%) ✔ ✔ ✔
sodium hydroxide (10%) ✔ ✔ ✔
organic
solvents
isopropyl alcohol ✔ ✔ ✔
toluene ✔ ✔ ✔
acetone ✔ increased* ✔
benzene ✔ ✔ ✔
xylene ✔ ✔ ✔
hexane ✔ ✔ ✔
*PTFE membrane intact but support layer affectedThanks to:
Nippon Muki, Tokyo, Japan,
for conducting these tests.
Pressure drop comparisionglass media vs. ePTFE HEPA
*this MEGAcel I to be tested by DPCnominal air flow
Oil loading behavior HEPA filtersmicroglass vs. ePTFE vs. eFRM media conventional ePTFE, PAO tolerant eFRM
592mm x 592mm x 69mm filters; PAO loading rate 45µg/l
Thanks to:Milholland & Associates, Holly Springs (NC), USA,
for conducting these tests.
eFRM
eFRMeFRMeFRMeFRM
Soot loading test HEPA filtersmicroglass vs eFRM media
15filter type I
Volume flow 3.400m3/h
ave. loading time 700min
ave. soot concentration 540µg/m3
ave. soot mass deposited on filters 21g
Nitrogen Gas
Diesel Tank
Soot Generator
Soot
Photometer
Test Duct
Particle Sizer
microglass eFRM
MPPS 100nm 79nm
ave. efficiency@MPPS (EN1822-5)
99,9835% 99,9985%
Soot loading test HEPA filtersmicroglass vs eFRM media
microglass
eFRM
Why AAF Membrane Technology?
High Collection Efficiency
H13 – H14 eFRM
H13-U17 ePTFE
Low Pressure Drop
Up to 50% lower
Reduces energy cost
Reduces construction depths
Low Off Gassing
Extreme low impurities
No Boron
Low Dopant Content
Improved yield
Reduced probability of contamination from filter
High Durability
Reduces transport and installation damage risk
Hydrophobic media
Media tensile strength is 84x that of standard micro-fiberglass media
High Chemical
Resistance
Hydrofluoricacid resistance
No media degradation from H2O2, alkaline, acid, and organic substances
Longer life expectancy
“The electric light did not come from the continuous improvement of candles.”
Prof. Oren HarariGlobal and Strategic Management University of San Francisco
Modern PTFE membrane based HEPA/ULPA filters for improved energy savings and risk reduction
Marc Schmidt, Ph.D.AAF International
Heppenheim (Germany)[email protected]
+49 175 18 788 78
Belgian Cleanroom Workgroup (BCW) – Cleanroom College Day 2019Ghent (Belgium)
Mar 21, 2019
