ASTM Tests for Oxidative Induction Time

ASTM RECOMMENDATIONS ASTM Tests for Oxidative Induction Time 

ASTM D 3895 Standard Test Methodfor Oxidative Induction Time of Polyolefins by Differential Scanning Calorimetry Note of the author This procedure cannot be used for filled composite materials regarding Sampling section, particularly for those employing rather large filler particles. Instead of compression-molded test samples into sheet format prior to analysis to yield consistent sample morphology and weight and cut specimen disks (6.4-mm diameter) from the sheet to have a 

OIT is a relative measure of a material s resistance to oxidative decomposition. It is determined by the thermoanalytical measurement of the time interval of exothermic oxidation of a material at a specified temperature (typically between 140 and 210°C) in an oxygen atmosphere. The procedure employs a differential scanning calorimeter (DSC). It is very practical to use an automatic sample, that is a carousel, which typically holds 50 specimens, and descriptions for 65 specimens can be programmed into the instrument before the runs. For low OIT numbers (less than 

1-2 min), the procedure takes about 30 min per specimen hence, 50 samples would run automatically for about 25 h, generating a wealth of data practically without an operator s involvement. For high OIT numbers, around 100 min, it wonld take almost 2 h per specimen. However, the instrnment allows to cnt the rnn after a specified time and automatically go to the next specimen. 

The sample to be tested is heated at a constant rate (nsnally 20°C/min) nnder a nitrogen atmosphere. When the specified temperatnre has been reached, the specimen is maintained at this temperature for several minutes (usually 5 min) to reach a thermal equilibrium, and the nitrogen atmosphere is changed to oxygen maintained at the same flow rate (usually 50 cc/min). The specimen is then held at the specified constant temperature until the oxidation reaction is displayed on the thermal cnrve. The time interval from when the oxygen flow is first initiated to the oxidative reaction is referred to as the induction period. The end of the induction period is signaled 

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