Resistance to oxygen

The iodides of the alkaU metals and those of the heavier alkaline earths are resistant to oxygen on heating, but most others can be roasted to oxide in air and oxygen. The vapors of the most volatile iodides, such as those of aluminum and titanium(II) actually bum in air. The iodides resemble the sulfides in this respect, with the important difference that the iodine is volatilized, not as an oxide, but as the free element, which can be recovered as such. Chlorine and bromine readily displace iodine from the iodides, converting them to the corresponding chlorides and bromides. 

SiHcone elastomers possess outstanding resistance to heat aging. The Si—O—Si backbone imparts resistance to oxygen, o2one, uv, and to some polar fluids. However, the strength of these elastomers is usually just adequate. They have low abrasion resistance and tear strength (see Silicon compounds, silicones). 

Rubber and Synthetic Elastomers. For many years nondecorative coated fabrics consisted of natural mbber on cotton cloth. Natural mbber is possibly the best all-purpose mbber but some characteristics, such as poor resistance to oxygen and ozone attack, reversion and poor weathering, and low oil and heat resistance, limit its use to special appHcation areas (see Elastomers, synthetic Rubber, natural). 

Ethylene—propylene elastomers exhibit a high resistance to oxygen, ozone, and heat, and are used in motor parts because of thek excellent low... 

Stainless steels contain 11% or more chromium. Table 5.1 lists common commercial grades and compositions of stainless steels. It is chromium that imparts the stainless character to steel. Oxygen combines with chromium and iron to form a highly adherent and protective oxide film. If the film is ruptured in certain oxidizing environments, it rapidly heals with no substantial corrosion. This film does not readily form until at least 11% chromium is dissolved in the alloy. Below 11% chromium, corrosion resistance to oxygenated water is almost the same as in unalloyed iron. 

Condensate returns lines are often copper. Copper has good corrosion resistance to oxygen and carbon dioxide individually. When both gases are present in the condensate, copper is susceptible to corrosion. Copper picked up in the condensate system and returned to the boiler causes serious corrosion problems in the boiler and any steel feedwater and steam pipework. Boiler tubes should last for 25 years but can fail within one year in a mismanaged or ill-designed boiler system suffering from these faults. 

Nylon barrier layers are used in packaging films and blow molded bottles. In these applications, their excellent resistance to oxygen permeation are valued when packaging greasy foods, such as potato crisps (chips), that rapidly turn stale when exposed to oxygen. 

As with chlorinated polyethylene rubber, chlorosulphonated polyethylene exhibits good resistance to oxygen, ozone and light. The polar nature of the polymer chain also confers oil resistance. 

The saturated main chain of the copolymer confers excellent resistance to oxygen, ozone and light, but means that these materials cannot be crosslinked by sulphur. Peroxides and radiation are the only methods by which crosslinking can be accomplished, and coagents are often required to achieve the required state of cure. 

The absence of any polar grouping gives this material superior low temperature performance when compared to the epichlorohydrin terpolymers, but this is at the expense of oil resistance. The unsaturated nature of the main chain confers excellent resistance to oxygen, ozone and UV light. 

The fluorocarbons have the best heat stability of all rubbers, being capable of giving extended service life at over 250 °C. As a group, fluorocarbons resist aliphatic, aromatic and chlorinated hydrocarbons, and most oils and mineral acids. They are also highly resistant to oxygen, ozone and UV light. 

Low maximum service temperature Not resistant to oxygen, ozone and light Not oil or solvent resistant... 

As expected, the materials exhibit the same morphology as the SBS types but the saturated midblock confers resistance to oxygen, ozone and UV light. Although it is said that improved phase separation gives improved stability to above ambient temperatures, the Tg of the polystyrene domains still restricts their use at high temperatures. 

The resistance to oxygen transfer across the air-water interface mainly exists in the water film. Therefore, Equation (4.22) should only be applied to compounds that are comparable to oxygen, i.e., according to Liss and Slater (1974), those that have an HA value greater than -250 atm (mole fraction)-1. 

Fe] hydrogenases are thus far only found in organisms growing under strictly anaerobic conditions. This makes it understandable that these enzymes are not tailored by Nature to be particularly resistant to oxygen and indeed this gas rapidly and irreversibly... 

Polyvinylidene chloride (PVDC), polyethylene (LDPE and HDPE), polypropylene (PP), PVC, and polystyrene all have excellent resistance to oxygen permeation. Polyethylene also has relatively good resistance to the permeation of water, which makes it an excellent choice for bread bags. 

Resistance to oxygen plasmas making bilevel schemes practical. 

As a result of its saturated polymer backbone, EPDM is more resistant to oxygen, ozone, UV and heat than the low-cost commodity polydiene rubbers, such as natural rubber (NR), polybutadiene rubber (BR) and styrene-butadiene rubber (SBR). Therefore, the main use of EPD(M) is in outdoor applications, such as automotive sealing systems, window seals and roof sheeting, and in under-the-hood applications, such as coolant hoses. The main drawback of EPDM is its poor resistance to swelling in apolar fluids such as oil, making it inferior to high-performance elastomers, such as fluoro, acrylate and silicone elastomers in that respect. Over the last decade thermoplastic vulcanisates, produced via dynamic vulcanisation of blends of polypropylene (PP) and EPDM, have been commercialised, combining thermoplastic processability with rubber elasticity [8, 9]. 

The nonpolar phases tend to have better characteristics in terms of resistance to oxygen, higher efficiencies, and greater maximum temperatures. Laboratories should have in their use at least two columns of different polarity. SE-54 phase can be regarded a better choice than OV-1 for the nonpolar phase because it provides better peak shapes for fairly polar chemicals such as thiodiglycol and... 

Tosatto SCE, Toppo S, Carbonera D, Giacometti G, Costantini P. Comparative analysis of [FeFe] hydrogenase from Thermotogales indicates the molecular basis of resistance to oxygen inactivation. Int J Hydrogen Energy. 2008 33(2) 570-8. 

---