The identiPol OIT

The lifetime of a plastic component is mainly governed by its ability to withstand oxidation and degradation. When exposed to the oxygen in the air that we breathe, plastics age and degrade over time, losing mechanical strength and leading eventually to component failure.

The lifetime of a plastic can be increased by appropriate polymer chemistry or by adding additives (antioxidants) to the plastic during processing. Generally, the lifetime is greater for materials having a higher molecular weight, although performance of lower specification plastics can be enhanced with anti-oxidants. However, as these additives are more expensive than the plastic granules, a balance is sought between cost and performance. The OIT test is frequently used as an indication of sufficient molecular weight, but in such cases it must be clear whether materials are tested with or without anti-oxidants.

The identiPol OIT is designed to provide unskilled staff with a simple tool to measure the oxidative stability of a plastic using the internationally recognised Oxidative Induction Time/Oxidative Induction Temperature (OIT) method. The system has been specifically designed to conform to approved standards (ASTM D3350, D3895-07, DIN EN 728, ISO 11357-6) and be operated alongside the production line by semi-skilled staff.

There are two modes of operation for the identiPol OIT:

When a plastic material undergoes oxidative degradation, heat is evolved. By measuring the temperature of the plastic and comparing it to the temperature of its nearby surroundings, a temperature difference can be measured when the plastic starts to oxidise.

Test samples are first moulded within the identiPol OIT to produce a consistent sample for measurement. The test sample is then heated up while the temperature difference of the sample is compared to an inert reference temperature. The temperature difference is then measured as the plastic is heated or held at a constant temperature.

Either the heating stops at a given temperature to measure Oxidative Induction Time, or continues to measure the Oxidative Induction Temperature. A rapid increase in the temperature difference between the plastic sample and the reference is used to indicate the onset of oxidation and decomposition.

At the end of the measurement the plastic sample is discarded and the built-in software calculates and stores all relevant information. A certificate of OIT conformance can be printed and used as part of your, or your customer's, quality control process.