regulatory compliant ptfe powders for grease applications
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COMPANY SENSITIVE & CONFIDENTIAL
Regulatory Compliant PTFE Powders for Grease Applications
NLGI 2021 Annual Meeting
Presented by: Shichiu Kwan
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COMPANY SENSITIVE & CONFIDENTIAL
Properties of PTFE Micropowders
Specific Gravity 2.20-2.30
Melting Point (˚C) 320-330
SolubilityInsoluble in all
solvents
Heat StabilityDecomposition starts
around 400˚C
Surface Area (m2/gram) 1-20
Surface Energy (mJ/m2) 18-22
Coefficient of Friction 0.04-0.10*
* Ebnesajjad S., Morgan R. 2012. Fluoropolymer Additives. 1st. Oxford, UK: Elsevier, Inc.
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COMPANY SENSITIVE & CONFIDENTIAL
PTFE Properties That Affect Performance
Type of PTFE
– Emulsion Polymerized
– Suspension Polymerized
– Recycled
Particle Size or Primary Particle Size (PPS)
Surface Area
Surface Properties
– Affected by irradiation dosage
Molecular Weight (MW)
– Controlled by irradiation dosage
Nature of PTFE
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COMPANY SENSITIVE & CONFIDENTIAL
Benefits of using PTFE Micropowders in Greases
Wide range of Operating Temperature
Chemically Inert/Resistant
Hydrophobic/Water Repellent
White or grey
Friction Modifier and Extreme pressure/Anti-wear Additive
More effective at high loads than liquid lubricant alone
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COMPANY SENSITIVE & CONFIDENTIAL
PTFE – where is it used
Thickener & Anti-Wear• PTFE is used as a thickener for PFPE oils, Silicone oils. Esters or other applications
where hydrocarbon based fluids will not work. • Food grade applications • Oxygen valve systems • Extreme temperature applications either high or low temperatures.
• Anywhere a standard / Conventional thickener will not hold up o Note: If used as a thickener it is the only thickener in the system.o Conventional thickeners , Bentone- Clay, Calcium , Aluminum complex,
Lithium, Lithium Complex Polyurea
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COMPANY SENSITIVE & CONFIDENTIAL
PTFE POLYMERIZATION
Particle Size
Mo
lec
ula
r W
eig
ht
Emulsion Grade/Paste PTFE
PS: 0.1-0.3 µm
MW: 1-5 million
Used to produce tape, fine tubing, wire coating
Suspension Grade/Granular PTFE
PS: 50-500 µm
MW: 5-50 million
Used to make parts or billets by sintering
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COMPANY SENSITIVE & CONFIDENTIAL
Nature of PTFE
Emulsion Grade
Small PPS
– ~0.2 µm
– 5-10 µm agglomerates
High BET Specific Surface Area (SSA)
– > 6 m2/g
SEM Picture of High MW
PTFE
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COMPANY SENSITIVE & CONFIDENTIAL
Nature of PTFE
Suspension Grade
Particle Size (MV)
– Originally 25-250 µm
– After micronization can be as small as 3-4 µm
Low Specific Surface Area (SSA)
– ≤ 3 m2/g
SEM Picture of High MW
PTFE
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COMPANY SENSITIVE & CONFIDENTIAL
Micronized PTFEMOLECULAR WEIGHT REDUCTION BY IRRADIATION
e*
e*e*
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COMPANY SENSITIVE & CONFIDENTIAL
Nature of Micronized PTFE
MW is controlled by irradiation/Higher dose gives lower MW
Irradiation improves friability or ease of de-agglomeration
MW affects PTFE performance in greases and lubricants
– Thickening efficiency directly proportional to MW
– Anti-wear performance inversely proportional to MW
Molecular Weight
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COMPANY SENSITIVE & CONFIDENTIAL
Formation of Small Molecules
Irradiation induced degradation of PTFE generates smaller radicals
Radicals react with oxygen and moisture to form carboxylic acid groups
A small fraction of these molecules are 8-carbons long
– Perfluorooctanoic Acid (PFOA)
– Concentration of PFOA is in the range of 0.1-10 parts per million (ppm)
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COMPANY SENSITIVE & CONFIDENTIAL
European Union Environmental Regulation (REACH)
REACH limits the concentration of PFOA
– 1 ppm (= 1000 ppb) until July 4, 2022
– 25 ppb after July 4, 2022
Other per- and polyfluorinated small molecules (PFAS)
– 1000 ppb total after July 4, 2022
Regulatory Compliance
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COMPANY SENSITIVE & CONFIDENTIAL
Process to Remove PFOA
Degraded PTFE heat treated to remove PFOA and other small molecules
Liquid Chromatography-Mass Spectrometry (LC-MS) is used to determine the concentration of PFOA
There is no globally accepted test method
Test method was developed using methanol extraction
Sensitivity of test is < 1 ppb
Products testing below 25 ppb are marked Regulatory Compliant (RC)
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COMPANY SENSITIVE & CONFIDENTIAL
Does PFOA Removal Process Affect PTFE Properties?
Properties that May be Affected
– Particle Morphology
– Surface Area
– Surface Polarity/Surface Energy
Could Result in Changes in Powder Behavior and Performance
– Thickening Capability
– Wear performance
– Dispersibility
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COMPANY SENSITIVE & CONFIDENTIAL
REM Pictures of Heat Treated Submicron PTFEs
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COMPANY SENSITIVE & CONFIDENTIAL
REM Pictures of Heat Treated Submicron PTFEs
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COMPANY SENSITIVE & CONFIDENTIAL
PTFE Thickening Efficiency
Thickening efficiency also depends on the base oil!
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COMPANY SENSITIVE & CONFIDENTIAL
PTFE Thickening Efficiency
Increases as Primary Particle Size decreases/Surface Area increases
Increases as Bulk Density decreases
– The lower the bulk density the more oil the PTFE will adsorb
– “Added by weight but volume fraction dictates rheology”
Increases with Molecular Weight
– Using an emulsion grade PTFE with same PPS and BD but much larger MW may lead to gummy consistency (at same loading in a given oil)
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COMPANY SENSITIVE & CONFIDENTIAL
Thickening Capability – Cone Penetration
The numbers are averages of all production lots made since January 2020
Emulsion Grade (Submicron) PTFEsSuspension Grade Virgin PTFE (5
Micron)
High MW
252 dmm
High MW-RC
253 dmm
High MW
340 dmm
High MW-RC
340 dmm
Medium MW
261 dmm
Medium MW-RC
260 dmmRecycle Grade PTFE (5 micron)
Low MW
271 dmm
Low MW-RC
271 dmm
Low MW
407 dmm
Low MW-RC
442 dmm
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COMPANY SENSITIVE & CONFIDENTIAL
4 Ball Wear Performance
High MW PTFE
Low MW PTFE
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COMPANY SENSITIVE & CONFIDENTIAL
4-Ball Wear Test Results(50% PTFE in PAO6)
Emulsion Grade (Submicron) PTFEsSuspension Grade Virgin PTFE (5
Micron)
High MW
0.53 mm
High MW-RC
0.55 mm
High MW
0.65 mm
High MW-RC
0.57 mm
Medium MW
0.51 mm
Medium MW-RC
0.52 mmRecycle Grade PTFE (5 micron)
Low MW
0.50 mm
Low MW-RC
0.50 mm
Low MW
0.60 mm
Low MW-RC
0.59 mm
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COMPANY SENSITIVE & CONFIDENTIAL
Zeta Potential -using Zetasizer Nano zs
The numbers are averages of all production lots made since January 2020
Emulsion Grade (Submicron) PTFEsSuspension Grade Virgin PTFE (5
Micron)
High MW
-39.4 mV
High MW-RC
-37.2 mV
High MW
-47.9 mV
High MW-RC
-39.4 mv
Medium MW
-39.6 mV
Medium MW-RC
-37.2 mVRecycle Grade PTFE (5 micron)
Low MW
-48.0 mV
Low MW-RC
-37.5 mV
Low MW
-61.9 mV
Low MW-RC
-29.7 mV
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COMPANY SENSITIVE & CONFIDENTIAL
Summary
Does PFOA Removal Process Affect PTFE Properties?
Properties that May be Affected
– Particle Morphology – Some change
– Surface Area - No
– Surface Polarity/Surface Energy – Yes, as indicated by Zeta Potential
Could Result in Changes in Powder Behavior and Performance
– Thickening Capability – Typically No
– Wear performance – Typically No
– Dispersibility – Typically No for PAO, Silicon, and PFPE oil. May change in Polar systems
COMPANY SENSITIVE & CONFIDENTIAL
Thank you for your attention!
Q&A
Contact: Shichiu Kwan
Email: Skwan@shamrocktechnologies.com
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