Afton Chemical tailors metalworking solutions to meet user application needs by combining our state-of-the-art R&D facilities around the world with our unique collaborative development process. Afton experts are actively involved with industry organizations to keep in close contact with our customers and understand their evolving needs. Our participation in these organizations also enables us to share Afton insight and stay updated on the latest industry trends. Karen Harrington, a Metalworking formulating specialist at Afton, recently presented on how to test and fix common issues in metalworking fluid formulations at a meeting of the Chicago Section of the STLE.

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Semi-Synthetic MWF’s

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Concentrate & Emulsion Stability Issues for a Semi-Synthetic
Separation in Concentrate
HLB is off
Look at emulsifiers in product
• Find out the HLB and adjust accordingly
Gelling
Might occur in high oil semi(40%) where there is 10-20% water
– Adjust glycol or fatty acid or amine
Emulsion instability
Dilution is not as translucent as you would like
HLB is too low – adjust with higher HLB material
Adjust with fatty acid or try different glycols
Hard water instability
Try ether carboxylates
Chelating agents
Play with fatty acid and amine
Surfactant type

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Problem formula – Initial formula had stability issues and over time separation
would occur
Chemical Initial Formula Final Formula
Naphthenic Oil 38.0 36.0
PIBSA 10.0 10.0
Amine 10.0 10.0
Ester additive 12.0 12.0
C10 Carboxylic acid 2.0 2.0
Coupler, alcohol 1.0 1.0
Ethoxylated Fatty amines; HLB 11.5 4.0 4.0
Ethoxylated Fatty amines; HLB 4.2 0.0 2.0
RP Package 14.0 14.0
Water 8.8 8.8
Defoamer 0.2 0.2
Key takeaway:
The HLB was too high in the initial formula. After adjusting the HLB by increasing
Ethoxylated Fatty amines, an added benefit was that final formula had better
emulsion stability.

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Synthetic MWF’s

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Concentrate & Dilution Stability Issues for Synthetic Products
Separation in oven stability testing
Using additives with inverse solubility
Lower oven stability testing temperature i.e. try 40°C rather the 50°C to see if
this makes a difference
• What is the cloud point
Decide if that is acceptable
Artificially raise the cloud point with addition of higher cloud point surfactant to
meet concentrate stability requirements
Freeze/Thaw or Fridge Issues
Since the product is mostly water you would expect it to freeze but it should
remain clear and stable once it reaches room temperature
Could add a glycol or glycerin to help with this
True Synthetic will generally form clear solutions
Issues would arise when trying to emulsify esters into concentrate

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Example of True Synthetic
Chemical %
Water 64.0
Amine 19.0
Boric Acid 3.5
Glycol 4.0
C10/C12 acids 9.2

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Synthetic with Inverse solubility additives
Chemical %
Water 64.0
Amine 13.0
C10/C12 Acids 2.0
Boric acid 1.0
C8-12 Carboxylic acids 8.0
Block Co polymer 9.0
Copper passivator 0.3
Bactericide 1.0

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Best Practices in Quantifying Concentrate & Solution Stability

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Methods to Quantify Concentrate Stability
Appearance – visual
Is your product crystal clear w/o dyes and defoamers?
Very important – generally clear products do not fall apart
Concentrate (Neat) Product Stability Testing
Most MW manufactures give their products a 1 year shelf life
Need a method to quickly determine concentrate stability
4 samples (10-15 mL) in small scintillation vials
Initially testing should be done w/o defoamers and dyes, once a final formula is chosen
run stability testing with and w/o defoamers & dyes
Place one sample in the Oven @ 50°C, one in the Fridge (0°C), one in the freezer
(-15°C), and keep one at room temperature
Cycle samples in and out of the Oven, Fridge and Freezer over a 5 day period.
Each day samples are removed from the Fridge, Freezer and Oven and examined for
clarity, separation, gelling or floc; samples are allowed to equilibrate to room temperature,
samples should be clear and stable
After the 5 day period of cycling each sample should be clear and stable

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Methods to Quantify Concentrate Stability
Long term concentrate stability testing
Monitor the sample
Prepare 2 samples one w/o defoamers& dyes and one sample with
Place samples on your shelf, every week examine the appearance, note
any changes
Check emulsion stability monthly to make sure the emulsion stability has
not changed

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2017 © Afton Chemical Corporation, All Rights Reserved. Not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation
Methods to Quantify Dilution Stability
Dilution Stability Testing – 100 mL graduated cylinders
Test dilution stability in several different laboratory prepared water hardness;
• DI, 200 ppm, 500 ppm and 1000 ppm
Also keep some water in the fridge and check emulsion stability and strike in the cold water
(Hardness could vary depending on region)
Leave overnight at room temperature and evaluate emulsion stability the next day
For a soluble oil note mL of floating oil or cream
For semi-synthetics and synthetics note how appearance of solution changes
For a soluble oils evaluate the ease with which the product emulsifies into
water, sometimes referred to as Flash, Spontaneity or Strike
5 mL of concentrate is added to 95 mL of water (200 ppm) in a 100 mL cylinder
An initial assessment is made of the spontaneity/strike
Cylinder is then stoppered and inverted slowly, one inversion 180° turn
Count how many inversions are required to completely disperse the concentrate into the
water

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Methods to Determine Dilution Stability
DIN method 51367 % Percent emulsion stability
1L of emulsion (with approx. 350 ppm water) is prepared and poured into a separatory funnel
Run an acid split on freshly prepared sample of the lower portion
After 24 hours draw off another sample and run another Acid split
Compare the two values
Recirculating tests in a bath, either aquarium or 4 L Beakers equipped with small
pump
Prepare enough dilution to fill recirculating bath
Test runs for 30 days
On day 1 of the test measure physical properties such as pH,
concentration by refractometer, conductivity, appearance, etc.
Each week re-test properties
Particle Size analysis
Emulsion stability is directly related particle size
Various instruments to measure Coulter Counter, Zetasizer,
Turbiscanner

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Summary

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Wrap Up
Many tools available to formulate metalworking fluids and help fix issues with
metalworking fluid formulations
Emulsifiers
Couplers
Common formulating issues include
Gelling of concentrate
Instability of concentrate
Poor emulsion formation
Formulating issues can be fixed
Rigorous stability testing during development will help prevent future field
related issues
Detailed documentation of development and manufacturing process can
facilitate root cause analysis should you encounter future field related issues