Air-oven test

In polypropylene in an air oven test at 140°C (PP ), on the other hand, the lower members of the series are completely ineffective, as is BHT. The highest member of the series, the commercial antioxidant IRGANOX 1076 (III, R = ClgH37) is highly effective under these conditions. 

Volatility and Migration Rate. A study of the half-lives (T ) of the antioxidants in the polymer (see Table 1) at the same temperature suggests a reason for the lack of correlation between the two sets of results. In an oxygen absorption test, volatilization cannot occur, and the result is a true measure of the intrinsic activity of the antioxidant molecule. In an air oven test, on the other hand, physical loss of the antioxidant by migration and volatilization from the surface must dominantly influence the test results. Billingham and his coworkers ( 2) have shown that these two physical parameters determine the rate of loss of antioxidants from polymers. Increase in molecular mass generally decreases molecular mobility as well as volatility, and which factor dominates depends on the thickness of the sample ( 2). 

Figure 1. Comparison of bound antioxidant (BHBM) with a conventional bisphenol in NR (air oven test at 100 °C).

Table 10. Changes in Mechanical Properties of NBR Vulcanisates Containing Bound Antioxidants in a Cyclical Oil/Air Oven Test at 150 CC.

The unsaturation and hydroperoxides formed initially in the polymer during the early stages of processing both disappear as a result of the peroxide catalyzed thiol addition to the double bond (41, 42). The resulting BHBM-B is a very powerful thermal antioxidant in an air oven test at 140°C (41), see Figure 9. EBHPT can be similarly bound to PVC to give an effective UV stabilizer (42). 

In a wide-mouthed test-tube ( boiling tube ) place 5 g. of phenol, 15 ml. of 40 per cent, formaldehyde solution and 3 ml. of concentrated ammonia solution (sp. gr. 0-88). Warm the mixtme with a small flame until it becomes opaque. Cool, discard the aqueous layer, but retain the viscous material in the tube. Heat the latter in a water bath at 60° for 30 minutes and then heat the pasty mass in an air oven at 75° for 4-6 hours. A hard sohd resin is produced. 

Thin-Film Oven Test (ASTMD1754). This test has the purpose of determining the hardening effect of heat and air on a static film of asphalt when exposed in a thin film. An analogous procedure is the Rolling Tbin-Film Test (ASTM D2872) which has the same purpose but utilizes a moving film exposed for 75 min at 163 °C. 

There is second shear adhesion test that is now being reported with increasing frequency, the so-called SAFT, or shear adhesion failure temperature test. It is particularly popular among block copolymer PSA developers. In this test [15], a shear specimen with an overlap area of 2.54 cm x 2.54 cm is prepared and suspended in a circulating air oven. A 1-kg weight is attached to the tape and the oven temperature is raised continuously 5.5°C per 15 min until failure. An industry wide standard has not yet been written for this test. 

These packets, usually six to twelve for a given film, were placed in the 100 °F circulating air oven on edge in an open top box. In this manner both liquid and vapor space tests are made simultaneously in case there are unexpected differences. 

In addition to normal compression set test conditions, usually 22 hours at 70 °C in a hot air oven, pharmaceutical elastomeric closures may be subjected to compression set conditions simulating steam sterilization cycles in an autoclave for 30 minutes at 121 °C. Also, sterilizing cycles employing ETO, radiation, or dry heat are used. Comparison data between formulations are used to develop compression set values that will identify potentially acceptable compounds under these conditions. 

The filled oven test pallets are loaded into a hot air oven and the munitions are heated to 210 F and then maintained at that temperature for 15 minutes. The munitions are then returned to the UP plant for leak inspection, palletization and storage or transfer to an ammunition loading plant. 

Other test methods are the powder bulk, aerated, and layer tests [137,138]. Several systems in-house built are available. All of these tests operate on the principle that a layer of the substance under investigation is heated in a circulating air oven as the temperature is increased. Air is transported through the sample (in the aerated test, the air flow is downward through the sample), and the temperature of the powder at several places is recorded. 

A 100-mL aliquot of filtered fuel is placed in a borosilicate glass container. The container is placed in a pressure vessel which has been preheated to 194°F (90°C). The pressure vessel is pressurized with oxygen to 800 kPa (absolute) (100 psig)for the duration of the test. The pressure vessel is placed in a forced air oven at 194°F (90°C) for 16 hours. After aging and cooling, the total amount of fuel insoluble products is determined gravimetrically and corrected according to blank determinations. 

A 1-L H2S-inert test container (glass test bottle) is filled to 50 vol % with fuel oil from a filled H2S inert container (glass sample bottle) just prior to testing. In the test container, the vapor space above the fuel oil sample is purged with nitrogen to displace air. The test container with sample is heated in an oven to 140°F (60°C) and agitated on an orbital shaker at 220 rpmfor three minutes. 

A yellow coloration of the fused mass indicates chromium. The mass is taken up in the platinum dish with water and acetic acid then added a little at a time until the reaction is acid. In a small portion of the acetic acid solution the presence of chromium may be confirmed by means of lead acetate. The acetic add solution and any undissolved part of the mass are concentrated to a small volume in a porcelain dish over a naked flume and then taken to dryness on a water-bath. The residue is heated for some time in an air-oven at iio° and then treated with water and hydrochloric acid and filtered. The filtrate is tested for tin and copper by means of hydrogen sulphide. 

The similar rate of decomposition of Tetralin hydroperoxide by distearyl and dilauryl thiodipropionate at 80 °C. is of interest when compared with the formers better antioxidant properties in polypropylene at 140 °C. Tests showed that the stearyl compound was superior to the lauryl compound as a synergist, in the presence of a phenolic antioxidant, in delaying the embrittlement of polypropylene sheet in an air oven at 140°C. (Table IV). 

Some applications require materials which are continuously or intermittently in contact with aqueous systems. Therefore, it is desirable to evaluate resins in a simulated test to determine water-extraction resistance (3). A commonly used test is the so-called seven-day boiling water test. Samples of 25-mil thickness were treated with boiling water for four and seven days (water changed daily) and then exposed in a circulating air oven at 125 °C. The relative stabilities are shown in Figure 1. The data... 

Figure 2. U-tuhe vs. oven test in oxygen and air with 25-mil samples at 140° and 150°C.

For each paper, both Foldur Kraft and newsprint, there were ten sample sets and one unwashed set, which was used as a control. The air dried samples were subjected to accelerated aging in humid (90°C/50% relative humidity) and dry (100°C) circulating air ovens for one, two, three, and five weeks. At regular seven-day intervals one sheet from each sample set was removed and tested. 

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