Oxidation stability testing

Oxidative damage, role of ascorbic acid in preventing, 25 769 Oxidative degradation, 70 682 of gasoline, 72 399-400 Oxidative dehydrogenation, 23 342-343 Oxidative pyrolysis, 27 466 Oxidative stability, of olefin fibers, 77 229 Oxidative stability test, 72 400 Oxide crystal glass-ceramics, 72 641 Oxide-dispersion-strengthened alloys, 77 103-104... 

A further modification of the PMR-12F-71 resin comprises changing from the nadic endgroups to vinylphenyl endgroups, simply by using p-aminostyrene in the synthesis. This resin was called V-cap-12F-71 (see Fig. 37). The V-cap versions of PMR-II-50 (V-cap 11-50) and PMR-12F-71 (V-cap-12F-71) underwent a comparative long term thermal oxidative stability testing (112). Neat resin weight loss was measured at 343 °C in air over a period of 750 hours (Fig. 38). The data clearly indicate that the 12F-PMR resins exhibit excellent thermal oxidative stability and it also shows that the NE endcap is thermally less stable than the V-cap in the PMR-II series. 

Another ASTM test method, Potential Gum (D873), combines the existent gum and the oxidation stability tests to measure potential gum. A sample of gasoline is subjected to the oxidation stability test for 960 min, filtered to remove particulates, and then subjected to an existent gum test. The potential gum is expressed as the total (unwashed) gum in this test. 

For jet fuels, a visual rating of No. 1 or No. 2 is required at 260°C in the jet fuel thermal oxidation stability test (JFTOT-ASTM D 3241). Also, a pressure drop of less than 25 mm Hg is required in this test, As shown in Table XI, the 250°F+ product from hydrotreated Illinois H-Coal syncrude passes both parts of the JFTOT test, even when the jet fuel is not refined enough to pass three other specifications aromatic content, smoke point, and gum content. When jet fuels are prepared from coal-derived syncrudes, the smoke point appears to be the limiting specification. The gum content and end point specifications are met when the jet fuels are distilled at 600°F. 

Sharma, B. K., and Stipanovic, A. J. 2003. Development of a New Oxidation Stability Test Method for Lubricating Oils Using High-Pressure Differential Scanning Calorimetry. Thermochim. Acta, 402,1-18. 

The expected life of a diesel fuel is indicated by the oxidation stability test (ASTM D-2276). The test measures how much gum and sediment will be deposited after conditioning the fuel at 120°C in the presence of oxygen for 16 h. It roughly corresponds to a years storage at 25°C. A result of less than 20 mg/L of sediment and gum after the test is considered acceptable for normal diesel. 

Kinematic viscosities of the fluids were measured according to ASTM D-445, 1991b (63). For Oxidative Stability testing, micro-oxidation experiments were carried out using the Pennsylvania State University Micro-Oxidation Kit (64). ASTM D-97 was used for pour points and cold storage tests (65). 

A particularly useful application is the oxidation stability test in which the thermal activity of a specimen is followed in oxygen until a sudden large exotherm occurs. If the sample contains an oxidation inhibitor the onset of the exotherm will be delayed, compared to that of an uninhibited sample. The amount of this delay is a measure of the amount of oxidation inhibitor remaining. 

It is important to note that the alkenes produced in reaction (11.1) can eventually form particulates in the lubricant, a critical criterion used in oxidative stability tests to determine the capabilities of turbine lubricants. This is demonstrated by the oxidative stability test [7] used in the Defence Standards for UK MoD gas turbine lubricant grades OX-7 [8] and OX-26 [9]. 

Chevron attaches considerable practical importance to the results of their in-house Oxidator BN oxidation stability test performed on base stocks to which both oxidation catalysts and inhibitors have been added. Chevron s... 

Woo and co-workers [5] carried out polyolefin durability estimates by oxidative stability testing using DSC. 

Depending on the intended end use of the oil, oxidation stability will be measured or expressed in different ways. All of the oxidation stability tests are based on placing a sample of oil under conditions that will greatly increase the rate of oxidation. Buildups of reaction products are then measured. The American Society for Testing and Materials (ASTM) D-943 test is the most widely used. Conducted under prescribed conditions, it measures the time (in hours) for the acidity of a sample of oil to increase a specified amount. The more stable the oil, the longer it will take for the change in acidity to occur. 

Polymer applications of DSC are numerous and concern the determination of Tm (ASTM E 794), Tg (ASTM E 1326-03, ISO/FDIS 11357-2), specific heat capacity of a material (ASTM E 1269, ASTM D 4816), crystallisation temperature upon cooling (ASTM E 794), transition temperatures (ASTM D 3418, ASTM D 4419, ASTM D 4591), purity of a material [79,80], contamination outgassing (ASTM E 1559), reaction rates, sample composition, reaction kinetic constants (ASTM E 698), reaction mechanisms, thermal stability (ASTM E 537), minimum processing temperatures, heat of fusion and crystallisation (ASTM D 3417), heat of crystallisation (ASTM E 793), additive effects on a material, quality control of raw materials [25], discrimination between materials, detection of polymorphism [81], characterisation of thermally and UV cured materials (cure state, degree of cure) (ASTM D 2471, ASTM D 5028), oxidative stability testing, QIT (ASTM D 3895, ASTM D 3012, ASTM E 1858-03), etc. 

Given the need for faster speed and reliability in the analysis of oxidative stability or susceptibility to oxidation, oils and fats can be evaluated by accelerated oxidative stability tests. These tests may include increased temperature, addition of metals, increased oxygen pressure, storage under light, and agitation. The temperature increase is the most efficient way to perform this evaluation [18]. 

The induction time values obtained using the accelerated oxidative stability tests at different temperature ranges showed that there was a progressive decrease in the thermal stability of the oils due to a parallel increase in the temperature to 120 °C and 140 °C. 

Foods without natural or synthetic antioxidants become spoiled when oxidation takes place. An antioxidant can be defined as a substance that prevents the reaction of various food constituents with oxygen and prevents oxidative damage (Pszczola, 2001). Common oxidative stability tests monitor the formation of hydroperoxides (indicating primary oxidation products) using different standardized tests. 

Evaluation of Antioxidative Activity Using a Thermal Oxidative Stability Test... 

The work herein has shown the suitability of P-DSC as an accelerated oxidation stability test method for biodiesel. Different biodiesel blends (B7) were compared in terms of their oxidative stability by P-DSC using dynamic (linear heating up to oxidation) and isothermal modes (maintaining constant temperature at a fixed value up to oxidation). The OOT and OIT parameters were determined for each studied blend and the positive influence of chain-breaking type additives (such as amine and/or phenolic compounds) has been shown. BHT showed better results (high OOT and OIT values) than TBHQ, but EAP, which is a mixture of 1 amine and 2 phenolic compounds, was by far the best AO. Synergetic effects could explain these very good results. 

Precautions—Very small amounts (as low as 0.001 %) of some materials, such as inhibitors, have a considerable effect upon oxidation stability tests. Avoid contamination and exposure to light while taking and handling samples. To prevent undue agitation with air, which promotes oxidation, do not pour, shake, or stir samples to any greater extent than necessary. Never expose... 

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