Oxidative Induction Time and Temperature OIT

A plot of oven resistance times compared to oxidative induction time (OIT) in an Arrhenius diagram for PE-HD [86] 

It is general knowledge that there is no correlation between oxidative induction time and long-term properties, because the OIT procedure is performed far above melt temperature. These high temperatures cause chemical reactions that are not activated at lower temperatures in addition, some additives may dissipate at these temperatures [177]. Stabilizers accumulate in the amorphous zones of semicrystalline thermoplastics. Subsequent to crystallite melting, their mobility and solubility increase abruptly. They spread out over the entire mass, while local concentration decreases [178]. 

Defining a specific oxidative induction temperature as a quality criterion for the stability of plastics against thermal oxidative degradation - as demanded by GRl-GM13 [176] for PE-HD geo-membranes — is arbitrary and not very informative. However, it has been used in industry for several years. The fact that a material has an oxidative Induction time of 100 minutes says nothing about the quality of the material In service and its service life [177]. 

Even so, oxidative induction times and/or -temperatures are important as quality criteria if the stabilizer package is known or at least unchanged, s. Section 2.1.3.4.2. 

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