Measurement of Oxidation Induction Period Time of Silicone Rubber by Differential Scanning Calorimeter

Silicone rubber is widely used in aerospace, electronic and electrical, automotive manufacturing and other fields due to its excellent properties such as high temperature resistance, aging resistance, and weather resistance. In long-term high-temperature service environments, silicone rubber is prone to oxidative degradation, leading to a decrease in mechanical properties and a shortened service life. The oxidation induction period (OIT) is a key indicator for evaluating the material's antioxidant stability, directly reflecting the thermal aging resistance of silicone rubber under high-temperature aerobic conditions.

   1、 Operation steps of the experiment

1. Samples and Sampling

Sample: Silicone rubber sealing strip formula rubber (or vulcanized finished sheet)

Sampling principle: Avoid surface pollution and oil stains; Try to take internal materials as much as possible (finished products can be scraped/sliced)

2. Measuring instruments

   DZ-DSC400 Differential Scanning Calorimeter(Nanjing DaZhan Testing Instrument)

3. Experimental parameter settings

Crucible: Open aluminum crucible (allowing oxygen to fully contact the sample; OIT generally does not recommend sealing)

Sample size: 10-15 mg

Gas: Nitrogen and Oxygen

Flow rate: commonly used 50mL/min

Heating rate: 20 ℃/min

Isothermal temperature: 200 ℃

Isothermal stability: N ₂ isothermal for 5 minutes after reaching 200 ℃ (stable baseline, residual oxygen removal)

Switching: Switching from nitrogen to oxygen at an isothermal temperature of 200 ℃

Record: Until significant oxidation heat release occurs, or set the maximum time (such as 200 minutes)

The recommended program segment is as follows:

4. OIT judgment and calculation

Under an oxygen atmosphere, silicone rubber begins to oxidize and releases heat deviating from the baseline; Using the "extrapolation starting point" to define the oxidation starting point: take the tangent of the rising segment of the oxidation heat release curve.

The oxidation induction period of the silicone rubber at 200 ℃ is 40.25 minutes, indicating that the material has good thermal oxidation stability at this temperature and can resist oxidative degradation for a long time.