ASTM oxidation index

Hydroperoxides determination is the key factor to measure the level and the behavior of the oxidation (Carlsson et al. 1987b, Lacoste and Carlsson 1991, Shen, Yu, and McKellop 1999). Scientific studies and the American Society for Testing and Materials (ASTM) oxidation index standard (ASTM F2102) usually give the quantity of ketones and other carboxyl species present as an index of the oxidation degree. It must be pointed out that ketones, though a product of the oxidative process, do not produce polymeric chain scissions and so they do not result in substantial reduction of tiie UHMWPE mechanical properties. Quantification of ketones is reliable only if the ratio between ketones and carboxylic acids remains constant through the entire oxidative process. 

The oxidation levels in the sterilized components were quantified using the ASTM oxidation index and found to vary considerably among radiation-sterilized polyethylene inserts, but not the gas sterilized inserts. None of the gas-sterilized components were found to contain detectable macroradicals, hydroperoxide content, or oxidation, regardless of whether or not they were highly crosslinked. 

FIGURE 16.6 ASTM oxidation index for (A) 30kGy irradiated in nitrogen and (B) 75kGy irradiated in air GUR 1020 specimens with 0-500ppm vitamin E and aged 0 weeks (ASTM F2003). Similar results were observed for GUR 1050. Adapted from [39]. 

Low oxidation (OI < 1) For ASTM oxidation index values of less than 1, it is very difficult to demonstrate a negative correlation with mechanical properties from retrievals, regardless of whether they are measured using miniature tension tests or small punch tests [16, 22, 34]. For this reason, oxidation indices of less than 1 may be considered relatively low, and despite evidence of early oxidative changes, it is unlikely that these changes have yet had a substantial negative impact on mechanical behavior. 

FIGURE 22.10 Average maximum ASTM oxidation indexes for the three categories of historical and conventional acetabular liners, summarized in Table 22.1 [42]. Substantial regional variation was observed in the maximum oxidation of retrieved liners ( significant differences in paired t-tests). 

FIGURE 14.4 The results of aging for 14 days at 70°C in 5 atmospheres of oxygen (ASTM F2003). The oxidation index is shown as a function of depth for X3 , N2A ac , 90TS and virgin UHMWPE after accelerated aging. 

Oxidation can also sometimes occur, which leads to carbonyl formation. Carbonyls, which include ketones, esters, and ethers, have a principal absorption peak around 1700cm ASTM F2102 desaibes the technique to measure the oxidation index, or the area of the carbonyl absorption peak ratioed against the methylene stretch at 1396cm [6-8]. 

Oxidative induction time (OIT) provides an index useful in comparing the relative resistance to oxidation of a variety of hydrocarbon materials. The OIT procedure was first developed in 1975 by Gilroy and coworkers at Bell Laboratory as a test procedure to screen polyethylene insulation used in telephone wire and cable for its oxidation resistance. The method first became available as a Western Electric Specification and later as ASTM Test Method for Copper-Induced Oxidative Induction Time of Polyolefins. Polyolefin manufacturers quickly embraced the procedure and began to apply it to other applications including raw resins, finished pipes, wire and cable insulation, and, most recently, geosynthetic waste pit liners (ASTM D3895 2009). 

NR, as a specific example is often selected according to its oxidation resistance. This may be assessed by measurement of its plasticity retention index (where Wallace rapid plasticity is measured before and after heat ageing at 140 °C, e.g., ASTM D3194-99 [21]). The drop in plasticity found after ageing is an indicator of this polymer s oxidation resistance. 

Nelson [136] has reported studies of zinc, zinc oxide, and zinc borate in coatings on or as a filler in modified polyphenylene oxide (m-PPO). Zinc arc spray, or zinc, zinc borate, and zinc/zinc borate in epoxy coatings showed a substantial reduction of flame spread index (ASTM E-162) (I,) for m-PPO. Zinc oxide in epoxy, however, showed a dramatic increase in I, on m-PPO. Zinc arc spray on m-PPO led to enhanced stability in the 500-600°C range in both isothermal and GC/MS experiments. It was speculated that since zinc melts at 420OC, just at the early stage of decomposition of m-PPO, this could allow intimate contact with the charring substrate. As in pure polystyrene, char formation is enhanced in air in m-PPO, and this was thought to be enhanced further by the presence of zinc. Indeed it was observed that volatilization of small molecules is reduced for m-PPO with zinc present at temperatures under 700°C, with preference for volatilization of the triaryl phosphate flame retardant, styrene trimer, and PPO dimers. 

We have found an extreme combustion behavior for a system polypropylene-polypropylene-co-polyethylene [238], It can be explained in terms of oxidative degradation of polymer materials. We studied the features of autooxidation and combustibility of blends of isotactic polypropylene (PP) and ethylene-propylene copolymers (PP-co-PE) as thin films (50-80 ). ASTM D2863 (ISO 4589 Part 2) was used to determine the oxygen index (LOI) for polymer films 140 by 52 mm. 

SCO derived from various yeast and fiingi should be thoroughly compared with vegetable oils in order to justify the possibihty to substitute for the current raw materials used for biodiesel production. SCO-derived biodiesel should conform with the requirements of quality biodiesel standards ASTM D6751 (USA), DIN 51606 (Germany), and EN 14214 (EU). The properties of biodiesel produced from SCO such as density, viscosity, heat of combustion, cold flow properties, flash point, cetane number, iodine index, and oxidative stability are dependent on its chemical... 

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