Depolymerization oxygen

Diol-functionalized telechelic polymers have been desired for the synthesis of polyurethanes however, utilizing alcohol-functionalized a-olefins degrades both 14 and 23. Consequently, in order for alcohols to be useful in metathesis depolymerization, the functionality must be protected and the oxygen atom must not be /3 to the olefin or only cyclic species will be formed. Protection is accomplished using a/-butyldimcthylsiloxy group, and once protected, successful depolymerization to telechelics occurs readily. 

When the films were treated in either an oxygen plasma environment or under UV/ozone irradiation, the rates of oxidation were faster for the plasma process. Irradiation of chitosan solution showed that UV/ozone induces depolymerization. In both plasma and UV/ozone reactions, the main active component for surface modification was UV irradiation at a wavelength below 360 nm [231]. 

The macrocyclic esters hold a special position among the industrially produced lactone fragrance materials. Like the well-known macrocyclic ketones, they have outstanding odor properties as musks. However, the lactones can be prepared more easily than the ketones, for example, by depolymerization of the corresponding linear polyesters. Since replacement of a methylene unit by oxygen affects the odor of these compounds very little, oxalactones with 15-17-membered rings... 

Figure 8. Effect of treatment severity on glycol lignin depolymerization in 2% NaOH. C/0 = carbon/oxygen ratio in residual lignins.

If, as a criterion of value to the study of lignin depolymerization by alkaline hydrolysis, the maximum yield of oxygen-bearing, phenylpropanoid derivatives is chosen, then the conditions of such a study have been optimized here at a treatment severity corresponding to a reaction temperature of 300°C for 1 hour. Under these conditions, 20% of the lignin is recovered as ether-solubles of which 55% is identifiable as monomeric derivatives. The rest of this material probably consists of dimeric-type compounds not identified by capillary gas chromatography. 

Barix process Barium is fust added to the resin in the form of a liquid hydroxide. Subsequently, the resin is heated in the absence of oxygen and broken into its original components. Barium plays the role of catalyst in this depolymerization process and reacts with the sulfur in the cationic functional groups to form barium sulfate, which in turn acts as a binder for the metallic species in the waste. Moreover, the barium hydroxide adjusts the pH so that the metals contained in the resins stay in the residue after the steps of drying and destruction (IAEA, 2002). 

It is essential that the oxidation of the glycol groupings in the polysaccharide be complete, and that no overoxidation occurs. The latter is excluded by performing the reaction with the exclusion of light, at low temperature, and at a pH of 3-3.5, as described by Bobbitt.73 The use of oxygen-free water and the addition of propyl alcohol, as a radical scavenger, also lessen radical-induced depolymerization during oxidation.75... 

Although reinforcements can improve the structural behavior of the composite at elevated temperature, the polymer, irrespective of its composition, begins to disassociate chemically in the presence of oxygen. Phthalic resins having the weaker ester bonds depolymerize readily at temperatures over... 

Kon. S. and S. Schwimmer , Active Oxygen Species Derived from Xanthine Oxidase Systems, Food Biochem., 1, 141 (1977). 

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