Composite anti-oxidants

The number of studies on the health effects of fullerenes and carbon nanotubes is rapidly increasing. However, the data on their toxicity are often mutually contradictory. For example, the researchers from universities of Rice and Georgia (USA) found that in aqueous fullerene solutions colloidal nano-C particles were formed, which even at low concentration (approximately 2 molecules of fullerene per 108 molecules of water) negatively influence the liver and skin cells [17-19]. The toxicity of this nano-C aqueous dispersion was comparable to that of dioxins. In another smdy, however, it was shown that fullerene had no adverse effects and, on the contrary, had anti-oxidant activity [20]. Solutions of prepared by a variety of methods up to 200 mg/mL were not cytotoxic to a number of cell types [21]. The contradiction between the data of different authors could be explained by different nano-C particles composition and dispersion used in research. 

The Armed Forces demand a long shelf-life (min 10-12 years) for propellants for use in different rockets and missiles. However, the shelf-life of propellants is limited. There are some chemicals which on their addition to these propellants during their manufacture retard the processes responsible for their deterioration and consequently, increase their shelf-life. The main purpose of addition of these chemicals in propellant formulations is to enhance their shelf-life without adversely affecting their manufacturing processes and properties. Such chemicals or additives are known as stabilizers in case of DB and composite modified double-base (CMDB) propellants whereas anti-oxidants in the case of composite propellants. The additives for this purpose are therefore selected depending on the type of propellant. 

Table 4.9 Some commercially available anti-oxidants for composite propellants.

Static evaluation of HTPB based composite propellants with potential anti-oxidants, unpublished work. 

One common feature of the mediterranean dietary habit is the use of olive oil as fat source in place of animal fat typical of Northern European and USA diets. As compared to other vegetable oils, olive oil is charaeterized by the peculiar composition of the tryglieeride fraction and by the phenolic and volatile constituents which affect the organolectic properties. Olive oil is rich in monounsaturated fat (56-84% of oleic acid), contains 3-21% of the essential linoleic aeid [3], is low in tocopherols [4,5] and therefore the presence of phenols is important to mantain the anti-oxidative stability. Several articles [1,2,6] reviewed the reasons why olive oil should be preferable to other dietary fat, paying particular attention to the fatty acid composition. Oleic acid is antithrombotic compared to saturated fatty acids [7]. Monounsaturated and polyunsaturated fats reduced low density lipoproteins (LDL) levels. 

Pellati F, Benvenuti S, Melegari M, Lasseigne T. Variability in the composition of anti-oxidant compounds in Echinacea species by HPLC. PhytochemAnal 2005 16 77-85. 

Specific fuel compositions and components measured include iso-octane, xylene, methylcyclohexane, naptha and California reformulated gasoline. Additives examined include anti-oxidant No. 29 (2,6-Di-Tert-Butyl-4-methylphenol), anti-oxidant No. 22 (N, N -Di-Sec-Butyl-P-Phenylenediamine) and DMA-548. 

In this paper, carbon fiber cloth reinforced SiC-ZrB2 composites (2D C/SiC-ZrBa) were prepared by slutiy infiltration of ZrB2 powders and precursor infiltration and pyrolysis (PIP) process to infiltrate SiC matrix, and accordingly mechanical property, anti-oxidation property, and torch ablation property were investigated. 

Lastly, the majority of the authors utilized products "chemically pure, "spectroscopically pure", "for analysis" purified or not in the laboratory. It is not certain whether this degree of purity is always sufficient. Certain values of G will probably have to be revised in the future. In particular, we must call attention to the fact that the polymers used in the radiolysis experiments are very often commercial polymers, that is they contain stabilizers, plastifiants, anti-oxidants, etc. and their exact composition is not indicated, he G s given in these cases have merely an indicative value. 

Even if several studies demonstrate that PBT is less stable than PET, less attention has been paid to the improvement of the stability of poly(bntylene terephthalate). [7,8] The nsnal strategy to increase PBT stability is the addition, dnring the synthesis or the mannfactnring, of anti-oxidizers, like Ultranox and Irganox the typical phenol-type radical scavengers. [20] However, dnring the last years, a good nnmber of new catalytic systems are claimed to catalyse efficiently PBT synthesis, but in these studies very few information are available about possible relationships between catalyst composition and polymer stability. [21-23]... 

While not useful in the polymerization stage, inhibitors have the important function of allowing safe storage of monomer when present in amounts of about 0.05%. They are important also in controlling the stability of unsaturated polyester compositions (Chapter 16), and most inhibitors function as anti-oxidants (Chapter 12) since oxidation processes are largely free radical processes. 

ENR prepared from chemical modification of NR latex has recently been commercialized. ENR was claimed to have oil resistance property, low gas permeability and more anti-oxidizing and damping than NR. Up to now, many research works have studied its applications and their blends with other polymers such as in this case, the blend between ENR and neoprene (CR) of which the effect of blending ratio on processability of ENR/CR blend was studied by Chiu et al Mastication of ENR (ENR-50, Malaysian Rubber Producers Research Association), CR (ES-2-16K, Du Pont), vulcanizing agent, accelerator, and other related ingredients was carried out in a pressurized kneader (SYD-5, Star-King Enterprise Co., Taiwan) for 17 min under a rotation rate of 77 rpm. Each sample s composition was listed in Table 18.7. 

The conq)osition of milk reflects to a certain extent he composition of he feed given to he cow. Consequently, inherent hctors in milk of relevance to he anti-oxidative balance will change depending on he feed composition and hereby influence he oxidative stability of he milk. 

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