Ozone initiation

Since the mid-1950s several materials have been found effective in combating ozone-initiated degradation, in particular certain p-phenylenediamine derivatives. The actual choice of such antiozonants depends on the type of polymer and on whether or not the polymer is to be subject to dynamic stressing in service. Since antiozonants are not known to have any use in plastics materials, even those which may have certain rubber particles for toughening, they will not be dealt with further here. Anyone interested further should consult references 3-5. 

The most prevalent approach to achieve long-lasting and nonstaining ozone protection of rubber compounds is to use an inherently ozone-resistant, saturated backbone polymer in blends with a diene rubber. The ozone-resistant polymer must be used in sufficient concentration (minimum 25 phr) and must also be sufficiently dispersed to form domains that effectively block the continuous propagation of an ozone-initiated crack through the diene rubber phase within the compound. Elastomers such as ethylene-propylene-diene terpolymers, halogenated butyl mbbers, or brominated isobutylene-co-para-methylstyrene elastomers have been proposed in combination with NR and/or butadiene rubber. 

Ozone initiates the chain oxidation of hydrocarbons in the gas [117] and the liquid phases [118]. 

It is not difficult to see that ozone initially forms from the oxygen present in the air. Chapman [115] introduced the photochemical model of stratospheric ozone and suggested that the ozone mechanism depended on two photochemical and two chemical reactions ... 

Sleiman M, Destaillats H, Smith JD, Liu C-L, Ahmed M, Wilson KR et al (2010) Secondary organic aerosol formation from ozone-initiated reactions with nicotine and second hand tobacco smoke. Atmos Environ 44 4191 198... 

Both the time of analysis and experimental design may affect the results. An explanation for the increase in adenylates under the conditions of our experiment is still needed. Since both ATP alone and total adenylate concentrations have increased, it does not appear that a shift in phosphorylation can account for the increases. The decrease in photosynthesis and increase in adenylates occur during the same time period and both factors return to normal after 21 hr. From previous research we know that the photosynthetic levels of ozonated pinto bean foliage decrease immediately after ozone exposure even when symptoms do not develop ( ). This does not hold true for the adenylate or respiration responses. Therefore, it appears that the ozone-initiated increase in adenylates is not correlated directly to the photosynthetic response. The increase in respiration persists when adenylate content and photosynthetic rates have returned to normal. Impaired mitochondrial function appears to be a secondary response more closely related to symptom development. 

Products of Ozone-Initiated Chemistry in a Simulated Aircraft Environment... 

H. and Nazaroff, W.W. (2008) Secondary organic aerosol from ozone-initiated reactions with terpene-rich household products. Atmospheric Environment, 42, 8234 15. 

Fan, Z., Iioy, P., Weschler, C., Fiedler, N., Kipen, H. and Zhang, J. (2003) Ozone-initiated reactions with mixtures of volatile organic compounds under simulated indoor conditions. Environmental Science ej Technology, 37 (9), 1811-21. 

Wang, H. and Morrison, G.C. (2006) Ozone initiated secondary emission rates of aldehydes from indoor surfaces in four... 

Weschler, C.J., Wisthaler, A., Cowlin, S., Tamas, G., Strnm-Tejsen, P., Hodgson, A.T., Destaillats, H., Herrington, J., Zhang, J. and Nazaroff, W.W. (2007) Ozone initiated chemistry in an occupied simulated aircraft cabin. Environmental Science g Technology,... 

Ozone initiates chain oxidation of hydrocarbons both in the liquid and gaseous phases. 

In the ozonation of tri-n-butylamine at —40°C. with an ozone-nitrogen stream, 1.2 to 1.6 mole equivalents of ozone were absorbed, and the yields of tri-n-butylamine oxide were 53% from chloroform and 6% from pentane solvents. The other products were the side chain oxidation products described by Henbest and Stratford (II). These results eliminate the possibility that the side chain oxidation is an ozone-initiated autoxidation. The mechanism outlined by Reaction 3 explains nicely both the requirement of ozone itself as the oxidizing agent and the solvent effect observed. Solvents such as chloroform would be expected to solvate the ozone-amine adduct (lb) and make the abstraction of the proton in Reaction 3 difficult. Thus, loss of molecular oxygen to give the amine oxide becomes the major reaction (Reaction 2). In pentane solu-... 

SCHEME 10.3 The three steps of the chain reaction by which CFCs, such as CF2CI2, destroy ozone. Initially, the CFC molecule absorbs UV radiation and generates two radicals. In step (b), the CT radical destroys an ozone molecule, and this reaction forms a new radical, CIO, which combines with O in step (c) and regenerates the Cl radical. The newly generated CT radical repeats step (b). And the chain process continues, in principle indefinitely. 

Wisthaler, A., Tamas, G, Wyon, D.P., Strom-Tejsen, P, Space, D., Beauchamp, I, Hansel, A., Mark,T.D.,Weschler, C.J. (2005) Products of ozone-initiated chemistry in a simulated aircraft environment. Environmental Science Technology, 39,4823 832. 

Caronaldehyde is formed in the OH-initiatiated oxidation of A -carene in yields of 31-34% (Arey et al., 1990a Hakola et al., 1994). It is also formed in lower yields (8%) in the ozone-initiated oxidation of A -carene. 

---