Plasticizer Migration Testing Mechanisms and ISO 177

# Plasticizer Migration Testing Mechanisms and ISO 177 > **What does a migration test actually measure?** Migration describes the movement of plasticizer out of a plasticized compound into a contacting material, a liquid or the surrounding air. A migration test quantifies that movement under defined conditions of time and temperature. ISO 177 is the standardised method that places a specimen in contact with a defined absorbent medium and determines the plasticizer that has transferred. ## Three mechanisms behind one number A migration result is the sum of several mechanisms acting at once, which is why the test conditions decide the result as much as the formulation does. | Mechanism | What drives it | Where it shows up | | :--- | :--- | :--- | | Diffusion in the polymer | Concentration gradient and mobility | Migration into a contacting solid | | Volatilisation | Vapour pressure and temperature | Loss from the surface into air | | Extraction | Solubility in the contacting medium | Food, liquid or solvent contact | | Exudation to the surface | Compatibility limit of the compound | Bloom and tackiness in service | Understanding which mechanism dominates in your application tells you which test is relevant. A cable compound in hot air is a volatilisation problem. A gasket in contact with oil is an extraction problem. A thin flexible film in contact with a solid surface is a diffusion problem, which is where the absorbent-medium approach is used. ## What ISO 177 does ISO 177, Plastics: Determination of migration of plasticizers, is a standardised method in which a specimen is brought into contact with a defined absorbent medium under specified conditions, and the amount of plasticizer that transfers is determined from the mass change and the analysis. The specimen geometry, contact medium, temperature and duration are specified in the version of the standard in force, and they should be reported alongside the result so that two laboratories can be compared. | Practical point | Why it matters | Action | | :--- | :--- | :--- | | Standard version | Conditions differ between editions | Cite the edition used | | Specimen preparation | Thickness and surface affect the rate | Cut specimens to the specified form | | Contact medium | Determines the driving force | Use the specified absorbent | | Temperature and time | Set the measured migration level | Keep conditions identical across samples | | Sample conditioning | Moisture and heat history influence results | Condition uniformly before testing | ## Building a migration test programme A single test rarely answers a service question. A practical programme combines a standardised method for comparability with a service-related test for relevance. | Purpose | Suitable approach | Note | | :--- | :--- | :--- | | Compare formulations | Standardised absorbent medium method | Same conditions for all candidates | | Predict volatile loss in hot service | Elevated-temperature volatile loss | Relates to cable and automotive use | | Check contact with a specific medium | Extraction in that medium | Mirrors the real contact scenario | | Assess appearance risk | Storage and humidity cycling with surface inspection | Detects exudation and bloom | | Verify compliance | Method required by the applicable regulation or customer standard | Report conditions with the result | ## Frequently asked questions **Is a lower migration result always better?** Not automatically. Very low migration can indicate a plasticizer that is very compatible but also less efficient, so the result is read together with hardness, flexibility and process behaviour. **Can migration be compared between different plasticizers with one test?** Yes, if the specimens, conditioning and conditions are identical. That is the value of a standardised method such as ISO 177. **How does migration relate to exudation in service?** Exudation is the visible result of migration to the surface. A formulation near its compatibility limit can pass a short test and still exude after long storage or temperature cycling. **Which plasticizers show the lowest migration direction?** Higher molecular weight and better compatibility generally reduce migration; ESBO, which also acts as a co-stabiliser, and the higher molecular weight grades are used where permanence is the priority. ## Request a sample and test guidance Our team can advise on a migration test plan for your application and supply the grades you want to compare as a 1kg complimentary testing sample dispatched worldwide via DHL or FedEx. Trial order MOQ is 1 MT, and bulk shipments are loaded as 23 MT flexitank containers from Ningbo or Shanghai.