Ozone polyethylene oxide

The action of ozone-oxygen mixtures (2% ozone) on polyethylene in the temperature range from 25° to 109° C. and on polystyrene in the range from 55° to 154° C. has been studied. The products and the rates of the reaction were followed by the changes in the infrared spectra of the polymers during ozonization. The main products appear to be aldehydes and ketones in the case of polyethylene, while an ozonide or peroxidic complex, stable at intermediate temperatures, forms during polystyrene ozonization. The activation energy is of the order of 9 kcal. for polyethylene for polystyrene it is considerably less. Rates of ozonization and oxidation of deuterated polystyrenes indicate that tertiary carbons are the seat of oxidation reaction. 

The method was introduced by Landler and Lebel who determined the decomposition constants of ozonized polyethylene, pol5winylchloride, and polystyrene, without distinction between peroxides and hydroperoxides. Zeppenfeld demonstrated that only hydroperoxides in acidic medium can oxidize ferrous ions according to the following reactions ... 

Chlorosulfouated polyethylene (Hypalou) 250 Excellent resistance to oxidizing chemicals, ozone, weathering. Relatively good resistance to oils, grease. Poor resistance to aromatic or chlorinated hydrocarbons. Good mechanical properties. 

Ozone diffuses readily into amorphous region of the polyethylene (32) and oxidation probably occurs much deeper in the solid sample. Ozone also attacks the crystalline part of polyethylene but it has a slow initiation stage followed by more rapid oxidation (13). Because ozone does not diffuse into the crystalline regions (13.32). oxidation is restricted to the surface. The resulting oxidized functional groups on the crystalline regions will remain at the surface, whereas those formed in the amorphous region can diffuse into the bulk. 

A PP sample after ozonization in the presence of UV-irradiation becomes brittle after 8 hrs of exposure, whereas the same effect in ozone is noticeable after 50-60 hours.Degradation of polymer chain occurs as a result of decomposition of peroxy radicals. The oxidation rapidly reaches saturation, suggesting the surface nature of ozone and atomic oxygen against of PP as a consequence of limited diffusion of both oxygen species into the polymer. Ozone reacts with PP mainly on the surface since the reaction rate and the concentration of intermediate peroxy radicals are proportional to the surface area and not the weight of the polymer. It has been found that polyethylene is attacked only to a depth of 5-7 microns (45). 

Razumovskii and his colleagues appear not to have been aware of the work of Priest et al. and prefer to interpret their own results as supporting a mechanism that involves attack of ozone on the CH,—CH, unit in polyethylene. Rate constants for the reaction have not been measured, and no assessment of the role of other oxidizing species has been made. However, it is presumed that a high-pressure ozonizer was used and that ozone was the active species. 

Aldehydes tend to be more reactive toward carbonyl oxide than ketones in the recombination reaction (Scheme 9.14, step 3). As a result, tetrasubstituted alkenes generally fail to give normal ozonides604 but rather, 75 undergoes the side reactions indicated above. A new method of ozonation carried out with alkenes adsorbed on polyethylene, however, could yield ozonides of tetrasubsituted alkenes, and even diozonides of dienes could be isolated.605... 

Chlorosulphonated polyethylene was first introduced by DuPont as Hypalon, a trade name in the year 1952. Chlorosulphonated polyethylene compounds have good heat and oxygen and ozone resistance, moderate oil resistance and excellent electrical properties, but their main features for use in the chemical process industries is their resistance to strong oxidizing chemicals. 

Polyethylene in solution is treated with chlorine and sulfur dioxide to introduce approximately 1.39k sulfur and 29% chlorine into the polymer. Most of the chlorine is attached directly to the carbon atoms in the backbone of the polymer, The remainder is in the form of sulfuryl chloride groups, SO CI, through which crosslinking occurs In the curing step with metal oxides. The material has good oxidation and ozone resistance and thus overall excellent weather resistance. Calendered stocks are used for lining ditches and ponds, for example. 

Boutevin et al. [177-180] treated different types of wastes of polyolefins (more often low density polyethylene) with a mixture air/ozone. They focused their studies on the quantification of the formed oxygenated species based on colorimetric titration using stable radicals such as diphenylpicryl-hydrazyl. They investigated the influence of mineral compounds (iron oxide, for example) used as catalysts for oxidative reactions. The ozonized polymers have been used as binders for composites materials containing mineral materials (sand, stones, etc.). 

The modification of the chemical composition of polymer surfaces, and thus their wettability with chemical substances, can be realized in different ways electric discharges more commonly called Corona effect, oxidation by a flame, plasma treatment, UV irradiation and also UV irradiation under ozone atmosphere. Numerous studies have been devoted to the effects of these different treatments. More recently, Strobel et al. [204] compared the effects of these treatments on polypropylene and polyethylene terephthalate using analytical methods such as E.S.C.A., F.T.I.R., and contact angle measurements. They demonstrated that a flame oxidizes polymers only superficially (2-3 nm) whereas treatment realized by plasma effect or Corona effect permits one to work deeply in the polymer (10 nm). The combination of UV irradiation with ozone flux modifies the chemical composition of the polymers to a depth much greater than 10 nm, introducing oxygenated functions into the core of the polymer. 

The formation of oxygen anion radicals and molecules of ozone also should be counted with at the ionization initiation of oxidation [26]. Initiation reaction caused by oxygen anion radicals may play an important role within the polymer bulk while the effect of ozone forming in the surrounding air atmosphere will include only the formation of radicals on the polymer surface. The latent effect of ionization initiation on polymer oxidation which is very distinct may be documented on a relatively fast increase of concentration of carbonyl groups, observed over 1 year after irradiation crosslinking of polyethylene [27]. 

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