What Is Chemical Resistance?
In the chemical resistance test, the sample is held in a defined chemical medium at a specific temperature and duration. Afterwards, the change in mass, dimensions, appearance and mechanical properties is measured. Its stressed variant (ISO 22088) reveals the risk of environmental stress cracking.
Purpose of Chemical Resistance
The purpose is to determine whether the product will withstand the chemicals in its service environment. One of the most insidious forms of damage in plastics is a chemical that seems harmless on its own initiating cracking under stress.
Which Products Is Chemical Resistance Applied To?
- Chemical storage tanks and pipes
- Automotive fuel and fluid systems
- Cleaning product packaging
- Laboratory and medical consumables
- Gaskets and sealing elements
In Which Sectors Is Chemical Resistance Used?
Standards Related to Chemical Resistance
- ISO 175 (determination of the effects of immersion in liquid chemicals on plastics)
- ISO 22088 series (determination of resistance to environmental stress cracking)
- ASTM D543 (resistance of plastics to chemical reagents)
- ASTM D1693 (environmental stress cracking of ethylene plastics)
Chemical Resistance Conditions
- Kimyasal ortam
- The item representing the service environment of the product; from specification
- Temperature and duration
- To reflect the service condition; from specification
- Gerilme durumu
- Free immersion or under constant strain/stress
- Quantities measured
- Mass and size change, appearance, hardness, tensile properties
Equipment for Chemical Resistance
- Chemical-resistant immersion vessels and temperature-controlled oven
- Analytical balance and dimensional measurement equipment
- Stress-holding fixtures (bent strip, C-ring)
- Tensile tester
- Fume hood and personal protective equipment
Sample Requirements for Chemical Resistance
- The sample must be taken so as to represent the batch or production run.
- Sample description, material type, and production direction if any, must be stated.
- The standard to be applied and any customer specification must be provided together with the sample.
- The test may be destructive; the required number of samples must be confirmed in advance.
- Surfaces that will be tested must be protected during transport.
Duration of Chemical Resistance
Immersion duration comes from the specification and can extend from days to months. Interim assessment points are planned to monitor the process.
Chemical Resistance Procedure
- 1The service environment is determined and the test chemical selected.
- 2Samples are prepared and initial measurements taken.
- 3Samples are fixed under the defined strain if required.
- 4Samples are immersed in the chemical and held at temperature.
- 5Samples are removed and examined at defined interim points.
- 6At the end, samples are cleaned and conditioned.
- 7Change in mass, dimensions, appearance and mechanical properties is measured.
Chemical Resistance Acceptance Criteria
The method standard defines how the test is performed, not what the result must be. The acceptance limit comes from the material or product standard, the customer specification, or the relevant regulation; this page therefore does not give a numerical limit.
Evaluation of Results
The result is given as percentage changes relative to the start and visual findings. The acceptance limit comes from the product specification. Cracking, blistering or noticeable swelling indicates the material-chemical pair is unsuitable.
Chemical Resistance Report
- Sample description, material/product information, and batch number if any
- Sample preparation method and conditioning conditions
- Standard and test conditions applied
- Instrument used and calibration status
- Measurement results and units
- Measurement uncertainty (if requested)
- A statement that the result applies only to the specimen submitted for testing
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Harmonised standards applied according to the product family
- EU 765/2008 (market surveillance and accreditation framework)
- Relevant product regulations and customer specifications
Plastics Testing — What Does This Testing Field Cover?
The section below describes the field that the Chemical Resistance test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Plastics testing determines the mechanical, thermal and burning behaviour of a polymer material. Unlike metals, plastics are VISCOELASTIC: their behaviour depends on loading rate, temperature and moisture. The same material therefore gives different results under different conditions, and the test conditions are an inseparable part of the result.
The practical consequence of viscoelasticity is this: a plastic part continues to deform over time under a constant load (creep) and the stress it carries at constant deformation falls over time (stress relaxation). A screwed joint loosens, a clamp loses its clamping force, a shelf sags over time. A short-term tensile test does not show this behaviour; a long-term test or an accelerated model is needed.
Thermal behaviour is the second main axis. Melt flow rate indicates the processability of the material and lot-to-lot consistency; heat deflection temperature and the Vicat softening point give a rough limit for service temperature. Thermal analysis (DSC, TGA, DMA) reveals the identity of the material: glass transition temperature, melting behaviour, crystallinity, filler content and decomposition temperature.
Burning behaviour is the third axis and ties directly into product standards. The UL 94 class and the limiting oxygen index are written into the material data sheet; a particular class is required for the housing of an electrical appliance, while a different classification system applies to a construction product.
Ageing is the most frequently skipped part of the field. Plastics degrade under UV, heat, moisture and oxygen: colour changes, the surface cracks, impact strength falls. For a part intended for outdoor use, what matters is not its values on day one but its values after ageing. Xenon arc and fluorescent UV equipment accelerate this degradation and allow comparison.
The output of this family is usually written into the material data sheet, and product standards refer to that sheet. But there can be a difference between the data sheet value and the behaviour of the actual part: orientation formed during moulding, weld lines and internal stresses make the part behave differently from the specimen.
The use of recycled content has added a new question to the field. Recycled resin varies from lot to lot; mechanical properties, colour and burning behaviour can shift between batches. For a manufacturer using recycled material, incoming material control is therefore not a choice but a necessity.
Method groups in this field
Mechanical
Tension, compression, bending, Charpy and Izod impact, hardness (Shore), creep and environmental stress cracking.
Thermal
Melt flow index (MFI), heat deflection temperature (HDT), Vicat softening temperature, linear thermal expansion.
Thermal analysis
Transition temperatures and crystallinity by DSC, composition and decomposition by TGA, dynamic mechanical behaviour by DMA.
Burning
UL 94 classification, limiting oxygen index (LOI), glow wire and needle flame tests.
Ageing
Accelerated ageing by xenon arc and fluorescent UV, hot air ageing, humidity and condensation.
Physical
Density, water absorption, ash content, gas and water vapour permeability of films and sheets.
Commonly confused in this field
- A plastics result without a stated test rate and temperature cannot be interpreted; viscoelastic behaviour depends on these parameters.
- A specimen result does not transfer directly to the actual part; moulding orientation and weld lines are decisive.
- HDT and Vicat values are NOT service temperatures; they are a rough indication of an upper limit and do not apply under load.
- The UL 94 class depends on thickness; a different wall thickness requires re-verification.
- For moisture-absorbing polymers (such as polyamide), results are misleading unless conditioning is carried out.
- ASTM D638 and ISO 527 results are not directly equivalent; the specimen geometries and rate definitions differ.
Which decisions these results support
- Material selection and supplier approval
- Meeting the flammability and thermal requirements of the product standard
- Verifying the use of recycled content and lot control
- Moulding process control and lot consistency
- Demonstrating ageing resistance for outdoor use
Related Tests
Frequently Asked Questions About Chemical Resistance
Why is it also tested under stress?
Many plastics cannot withstand under stress a chemical they resist when unstressed. Environmental stress cracking arises this way and explains a significant share of field fractures.
What should the test duration be?
The product's service condition determines the duration. The standard does not suggest a duration; the specification or risk assessment defines it.