KEVOS® MAKEOS · Materials
Solvent Attack and Swelling Screen for Plastics and Elastomers (Hansen Distance Ra and RED)
Will this solvent, cleaner or blend of two liquids dissolve or swell my plastic or rubber part, or will it dissolve the polymer I want to dissolve?
Hansen solubility parameter screen: the dispersion, polar and hydrogen-bonding parameters of a liquid or of a blend of two liquids mixed by volume, the Hansen distance Ra to the polymer with the dispersion difference weighted four times, the relative energy difference RED = Ra ÷ R₀ against the polymer’s interaction radius, the blend share that brings the liquid closest to the polymer, and a verdict for a part that must resist the liquid or for a liquid meant to dissolve the polymer, with a band of uncertainty around the sphere boundary.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| What the liquid must do | choice | Choose whether the part must resist the liquid or the liquid is meant to dissolve or swell the polymer. |
| Polymer | ||
| Polymer dispersion parameter δD | MPa½ | Dispersion parameter of the polymer from Hansen’s handbook, the material supplier or a solubility test with known solvents. |
| Polymer polar parameter δP | MPa½ | Polar parameter of the polymer from the same source as δD. |
| Polymer hydrogen-bonding parameter δH | MPa½ | Hydrogen-bonding parameter of the polymer from the same source as δD. |
| Polymer interaction radius R₀ | MPa½ | Interaction radius of the polymer’s solubility sphere, from the same source; it belongs with the three parameters above. |
| Liquid A | ||
| Liquid A dispersion parameter δD | MPa½ | Dispersion parameter of the first liquid from a table of Hansen parameters or the supplier. |
| Liquid A polar parameter δP | MPa½ | Polar parameter of the first liquid. |
| Liquid A hydrogen-bonding parameter δH | MPa½ | Hydrogen-bonding parameter of the first liquid. |
| Liquid B (second liquid of a blend) | ||
| Liquid B dispersion parameter δD | MPa½ | Dispersion parameter of the second liquid of a blend; leave the share at 0 % for a single liquid. |
| Liquid B polar parameter δP | MPa½ | Polar parameter of the second liquid. |
| Liquid B hydrogen-bonding parameter δH | MPa½ | Hydrogen-bonding parameter of the second liquid. |
| Share of liquid B in the blend by volume | % | Volume share of liquid B in the blend, from the recipe; 0 % for liquid A alone, 100 % for liquid B alone. |
| Decision | ||
| Uncertainty band either side of RED = 1 | How far either side of RED = 1 you treat as uncertain, from your own test experience with the polymer. | |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: What the liquid must do
- What it is
- Whether a good result means the polymer withstands the liquid, as for a part, seal or container, or that the liquid dissolves or swells the polymer, as for cleaning, solvent bonding or coating.
- Units and format
- Choose one of 2 options from the list: The part must resist the liquid; The liquid should dissolve or swell the polymer.
- Example
- The form opens with “The part must resist the liquid” selected as a worked example. Choose the option that matches your case.
- Effect on the result
- Reverses which side of the sphere passes; the distance and RED do not change.
- Get it right
- For a part that must resist, a borderline result is a reason to test, not to approve.
Polymer
What this means: Polymer dispersion parameter δD
- What it is
- The dispersion part of the polymer’s Hansen solubility parameter, from non-polar van der Waals attraction; with δP and δH it fixes the centre of the polymer’s solubility sphere.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 10 MPa½ to 30 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 18.5 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Differences in δD count twice as much as the others in Ra (weighted by 4 in Ra²).
- Get it right
- Keep all four polymer values from one source: the centre and radius are fitted together.
What this means: Polymer polar parameter δP
- What it is
- The polar part of the polymer’s Hansen solubility parameter, from permanent dipole attraction between molecules.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 0 MPa½ to 40 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4.5 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Different grades and copolymers of one polymer can have noticeably different polar parameters.
What this means: Polymer hydrogen-bonding parameter δH
- What it is
- The hydrogen-bonding part of the polymer’s Hansen solubility parameter, from hydrogen bonds and similar electron exchange between molecules.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 0 MPa½ to 50 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2.9 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Alcohols and water have large δH; a polymer with small δH usually resists them.
What this means: Polymer interaction radius R₀
- What it is
- The radius of the polymer’s solubility sphere in Hansen space: liquids closer than this distance to its centre dissolve or swell it, those farther away do not.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 0.5 MPa½ to 40 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 8.6 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- RED is Ra divided by R₀, so a larger radius makes every liquid look more aggressive.
- Get it right
- R₀ belongs to the same fit as the polymer’s parameters; never mix a radius from one source with a centre from another.
Liquid A
What this means: Liquid A dispersion parameter δD
- What it is
- The dispersion part of the first liquid’s Hansen solubility parameter; for a single liquid this is the liquid compared with the polymer.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 10 MPa½ to 30 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 15.5 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use values for the pure liquid; commercial cleaners are mixtures, so build them from their main components.
What this means: Liquid A polar parameter δP
- What it is
- The polar part of the first liquid’s Hansen solubility parameter.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 0 MPa½ to 40 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 9 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take all three liquid values from one table so they are consistent.
What this means: Liquid A hydrogen-bonding parameter δH
- What it is
- The hydrogen-bonding part of the first liquid’s Hansen solubility parameter.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 0 MPa½ to 50 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 19 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Water’s δH is very large, so small water contents can shift a blend noticeably.
Liquid B (second liquid of a blend)
What this means: Liquid B dispersion parameter δD
- What it is
- The dispersion part of the second liquid’s Hansen solubility parameter, used only when its share in the blend is above zero.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 10 MPa½ to 30 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 18 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Leave the share at 0 % to judge liquid A alone; the closest-blend result still uses liquid B.
What this means: Liquid B polar parameter δP
- What it is
- The polar part of the second liquid’s Hansen solubility parameter, used only when its share is above zero.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 0 MPa½ to 40 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.5 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Choose a second liquid on the far side of the polymer from liquid A to bring a blend inside the sphere.
What this means: Liquid B hydrogen-bonding parameter δH
- What it is
- The hydrogen-bonding part of the second liquid’s Hansen solubility parameter, used only when its share is above zero.
- Units and format
- Enter a number in MPa½: MPa½. The form accepts 0 MPa½ to 50 MPa½. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 MPa½ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Check that the two liquids are themselves miscible at the blend share chosen.
What this means: Share of liquid B in the blend by volume
- What it is
- The share of the blend’s volume that is liquid B; each blend parameter is the volume-weighted average of the two liquids’ values.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Moves the liquid’s point in a straight line from liquid A (0 %) to liquid B (100 %).
- Get it right
- Convert a mass recipe to volume shares with the liquids’ densities; evaporation of one liquid changes the share in use.
Decision
What this means: Uncertainty band either side of RED = 1
- What it is
- The width of the uncertain zone either side of the sphere boundary RED = 1, inside which the result is reported as borderline rather than a clear yes or no.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 0.9. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.1 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Only moves the lines between the clear and borderline verdicts.
- Get it right
- Base it on your own tests with the polymer; the boundary of a fitted sphere is not sharp.
Method and formulas
- Blend parameters are volume-weighted: δ = (1 − x)δA + x δB for each of δD, δP and δH.
- Ra² = 4(δD,liquid − δD,polymer)² + (δP,liquid − δP,polymer)² + (δH,liquid − δH,polymer)²; RED = Ra ÷ R₀, below 1 inside the polymer’s solubility sphere (Hansen).
- The blend share closest to the polymer minimises Ra², a quadratic in x, limited to 0 to 100 %.
- Example: liquid A (15.5, 9.0, 19.0) against a polymer at (18.5, 4.5, 2.9) with R₀ = 8.6: Ra = 17.76 and RED = 2.07, likely to resist; liquid B alone gives RED 0.38, and the closest blend, 91.1 % B, gives RED 0.33.
Limitations
- The sphere is an empirical screen: its boundary is not sharp and its values come from tests with a set of solvents.
- Time, temperature, stress, crystallinity, crosslinking and the size of the liquid molecules all change real attack and swelling; the screen does not model them.
- Environmental stress cracking can occur in liquids outside the sphere.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Screen whether a cleaner, solvent, fuel or process liquid will attack a plastic part or swell a seal
- Choose a solvent or blend for solvent bonding, coating or dissolving a polymer
- Design a two-liquid blend that dissolves a polymer neither liquid dissolves alone
- Decide which liquids need an immersion test before approval
Who it is for
- Design and materials engineers
- Maintenance and cleaning planners
- Coating and adhesive formulators
- Quality engineers
What you get
- Hansen parameters of the liquid or blend
- Hansen distance Ra and RED
- Blend share closest to the polymer
- Resist, borderline or dissolve verdict
Interpreting the result
- RED well above 1: the liquid is unlikely to dissolve the polymer, but test before approval; RED near 1: borderline, partial swelling is likely; RED well below 1: likely to dissolve an amorphous polymer or strongly swell a crosslinked one.
- Two liquids that each sit outside the sphere can, blended, sit inside it; the blend result shows when that happens.
Before relying on the result
- Run an immersion test of the actual part material in the actual liquid at the service temperature.
References
- Hansen C. M., Hansen Solubility Parameters: A User’s Handbook, 2nd edition (CRC Press, 2007): the three-parameter solubility sphere, Ra with the factor 4 on dispersion, RED and volume-weighted blends.
- Klenin V. J., Thermodynamics of Systems Containing Flexible-Chain Polymers (Elsevier, 1999; ISBN 0-444-82373-5), §3.1.1: Hildebrand’s solubility parameter, its split into dispersion, polar and hydrogen-bonding parts, and best solubility for close parameters. Method reference; no tables are reproduced.
- ISO 175, Plastics: methods of test for the determination of the effects of immersion in liquid chemicals; ISO 1817, Rubber, vulcanized or thermoplastic: determination of the effect of liquids. Consult the current editions.
Learn the Concepts Behind This Tool
These KEVOS® Library readings explain the method this tool uses, with worked examples.
Method explained here · KEVOS® original book
Preparing surfaces for bonding
In Adhesive Bonding by the Numbers
What it covers: The order of degreasing, abrading and cleaning, choosing a solvent that will not attack a plastic part, primers and conversion coatings, and keeping prepared parts above the dew point.
Method explained here · KEVOS® original book
Choosing solvents and cleaners with Hansen parameters
In Polymer Chains by the Numbers
What it covers: Screen liquids against a plastic with Hansen solubility parameters, blend two liquids to reach or avoid a polymer, pick a cement solvent and a safe cleaner, and know what the sphere cannot predict.
Method explained here · KEVOS® original book
Substitution, reduction and proof
In Solvent Vapours by the Numbers
What it covers: Choosing a less volatile substitute that still cleans and spares plastic parts, measuring use per part, proving a reduction with a fair trial, and the solvent balance before and after.
Useful alongside · KEVOS® original book
Plate or shell-and-tube
In Heat Exchangers by the Numbers
What it covers: Choose between gasketed plate, brazed plate and shell-and-tube exchangers on coefficient, approach, size, pressure, fouling and cleaning, and catch a brazed plate unit fed unstrained tower water.
Useful alongside · KEVOS® original book
Define the part before you draw the mould
In Plastic Parts by the Numbers
What it covers: Write a moulded-part brief covering function, loads, environment, appearance, assembly, volume and tolerances, then choose the process and material against it.
KEVOS® tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.