Oxidation stability oxygen uptake

Figure 10. Comparison of Chain Scission Rates in Stabilized and Unstabilized HDPE, Oxidation by Oxygen Uptake at 100°C and 1 Atmosphere...

The observation of an unusual effect occurring as a consequence of preannealing on the induction time of oxidation of PP stabilized with Irganox 1010 (Figures 19 and 20) needs to be taken into account when searching for correlations between induction periods from chemiluminescence and oxygen uptake for oxidation of PP stabilized with different types of antioxidants. 

D 4739 D 4742 Base Number Determination by Potentiometric Titration. Oxidation Stability of Gasoline Automotive Engine Oils by Thin Film Oxygen Uptake (TFOUT)... 

The exposed compounds also show a slow decrease In resistance to thermal oxidation at elevated temperatures, when measured by conventional techniques of oxygen uptake or thermal analysis. Table II shows typical thermal analysis data on samples weathered In New Jersey for 10 years. Similar measurements on compounds exposed for 30 years show that some thermal oxidative stability still remains In the bulk material. 

Recently we have been studying both the molecular weight changes and the physical property changes in HDPE as a function of oxidation. Unstabilized and stabilized HDPE were evaluated by oxygen uptake at... 

The polymer used was Alathon 5496, DuPont HDPE. The stabilizer used was tetrakis[methylene-(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane, referred to as A01. Powdered samples of HDPE, stabilized and unstabilized, were prepared and subjected to oxidation in a closed system with oxygen. Oxygen uptake was monitored periodically at given temperatures. The induction period was picked from the curve where the onset of autocatalytic oxidation took place. 

Figure 4. Arrhenius Plot of Stabilized and Unstabilized HDPE During Oxidation, Oxygen Uptake at 1 Atmosphere and Three Temperatures...

At 40°C the oxidation rate was slow but measurable for unstabilized HDPE. The stabilization provided by AOl for more than four years was evident from the oxygen uptake, elongation and molecular weight data. 

Table III. The evaluation of ABS thermal oxidative stability by the chemiluminescence, DSC and oxygen uptake methods...

It is known that ABS exhibits dramatic loss of impact resistance when aged in an air oven even at 130 C. The DSC and oxygen uptake methods are probably useful in estimating the high temperature performance but not necessarily directly applicable to predict life times at service temperatures (18). Thus the ability of chemiluminescence to be applied for evaluation of ABS thermal oxidative stability at 150°C and even lower temperatures seem to be important. 

Finally, candidate lubricants containing the antioxidants are tested in fleets of automobiles for thousands of miles. The engines are dismanded and examined for wear and coatings of varnish and other deposits. The lubricant is evaluated for sludge, viscosity, acidity, etc. Since evaluation in automobiles is expensive and time-consuming it is reserved for only the most promising candidates. Oxygen uptake tests are also used to measure oxidative stability (28). 

Stabilization of PP, HDPE, LDPE and LDPE/L-LDPE blends is the main application field of HAS [12]. The polymer matrix influences, to some extent, the efficiency. For example, the light stabilizing effect in LDPE/L-LDPE increased with the relative content of L-LDPE [140]. Differences in the rate of the oxygen uptake were found between 28, R = H doped PP and PE oxidized at 90 °C or irradiated with light having A >290 nm [141]. 

Lenoardi22 (Socony Mobil) worked with saturate and aromatic fractions from both raw distillate and the corresponding solvent extracted lube cut and measured oxygen uptake at 149°C. They found in both cases that saturates alone oxidized rapidly and were stabilized by addition of the aromatics fraction. An optimum aromatics level of about 5% to 10% was found for the raw distillate. Working with oxidized samples, they concluded that when oxidation took place, paradoxically... 

Numerous oxidation tests are available to screen vegetable oil oxidative stability including thin film oxygen uptake test (TFOUT, ASTM D 4/42), rotating bomb oxidation test (RBOT, ASTM D 2272), panel coker test, and pressurized differential scanning calorimetry (Biswas et al., 2007 Erhan et al., 2006 Sharma et al., 2005,... 

---