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Lab Methods

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Oxidation Stability

  • Method ASTM D525
  • Repeatability 0.05
  • Reproducibility 0.1
  • Blending non-linear
  • Additive Correction No

The purpose of this test is to determine the stability of gasoline in finished form only, under accelerated oxidation conditions.

The method is performed by adding sample at room temperature to a glass beaker inside of a metal bomb and sealing it. This metal bomb is then pressurized with 100psi of oxygen and placed into a bath heated to 212°F. If a leak is detected the test has to be reset. The pressure is then monitored until a “break point” is reached or the time specification has passed. The break point is reached when the sample begins to oxidize and the pressure inside the bomb drops before relieving the pressure.

When a sample fails on oxidation stability it can be a good indicator that it has a high tendency to form gums and insolubles in storage. Some of the leading contributors are a high presence of olefins. They have room to absorb oxygen and form new compounds. Aromatics and Saturates resist this and take a lot more energy to change form. There are additives that are designed to improve stability in products. Since no two products are alike these additives need to be evaluated in a lab environment.