Organic peroxide residues

Organic peroxides can occur in small amounts in some types of polymers such as polystyrenes as a result of the fact that a peroxide has been used as a polymerization catalyst in polymer manufacture. Also, stable organic peroxides such as dicumyl peroxide has been used as synergists, in conjunction with bromine and or phosphorus containing additives, to impart Are resistance to cellular expanded polystyrene and other types of plastics 

3a Polarographic Procedure. A polarographic procedure for the determination of p-tert-butyl perbenzoate in polystyrene is described in method 33. 

3b Thin Layer Chromatographic Procedure. Certain types of peroxides used in polymer formulations are extremely stable and unreactive. This applies to substances such as dicumyl peroxide used as an ingredient of some self-extinguishing grades of polymers. 

This substance cannot be determined by polarography and will not react with many of the reagent normally used for determining organic peroxides. 

Brammer et al have described a method for determining dicumyl peroxide in polystyrene, which is not subject to interference by other organic peroxides or additives that may be present in the polymer. The dicumyl peroxide is extracted from the polymer with acetone and then separated from any other additives present by thin-layer chromatography on silica gel. The gel in the area of the plate containing dicumyl 

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GC is extensively used to determine phenolic and amine antioxidants, UV light absorbers, stabilisers and organic peroxide residues, in particular in polyolefins, polystyrene and rubbers (cf. Table 61 of Crompton [158]). Ostromow [159] has described the quantitative determination of stabilisers and AOs in acetone or methanol extracts of rubbers and elastomers by means of GC. The method is restricted to analytes which volatilise between 160 °C and 300 °C without decomposition. A selection of 47 reports on GC analysis of AOs in elastomers (period 1959-1982) has been published... 

Thin layer chromatography has also been applied to reactive organic peroxide residues such as tertiary butyl perbenzoate and benzyl peroxide in polystyrene (Method 34). 

Applications As the basic process of electron transfer at an electrode is a fundamental electrochemical principle, polarography can widely be applied. Polarography can be used to determine electroreductible substances such as monomers, organic peroxides, accelerators and antioxidants in solvent extracts of polymers. Residual amounts of monomers remain in manufactured batches of (co)polymers. For food-packaging applications, it is necessary to ensure that the content of such monomers is below regulated level. Polarography has been used for a variety of monomers (styrene, a-methylstyrene, acrylic acid, acrylamide, acrylonitrile, methylmethacrylate) in... 

For peroxide cross-linking, organic peroxides, such as dicumyl, di-t-butyl, and benzoyl peroxides, are used in amounts 1 to 3 phr (parts per hundred parts of rubber). Typical cure cycles are 5 to 10 min at temperatures 115 to 170°C (239 to 338°F), depending on the type of peroxide used. Each peroxide has a specific use. A postcure is recommended to complete the cross-linking reaction and to remove the residues from the decomposition of peroxide. This improves the long-term heat aging properties.62... 

Organic peroxides and peroxodisulfates as well as some azo compounds and carbon-carbon compounds are mainly used as initiators in radical polymerization. The production volume of these initiators exceeds 250,000 metric tons. More than 50% of all polymers are made industrially by radical polymerization. Considering that the annual worldwide production of polymers is in the range of 200 Mio metric tons, it indicates that initiators have fundamental importance. The quantity of initiator used varies in a range from 0.01- 5% depending on the process and polymer applied (Fig. 1). Their decomposition products become incorporated or remain as a residue in this large volume of polymers (Fig. 2). 

Mitochondrial ADP-ribosylation as described by Kun et al. [2,4] involves the apparent transfer of ADPR residues from NAD to a 50 kD polypeptide. Yet another ADP-ribosylation reaction was reported by Richter et al. [13,14], They described the modification of a 30 kD polypeptide insubmitochondrial particles when incubated with labeled NAD. This reaction was brought into connection with Ca efflux from mitochondria as induced by treatment of mitochondria with organic peroxides. Such treatment was known to result in the concomitant degradation of NAD and NADP to ADPR and P-ADPR, respectively [15]. During our attempts to characterize these mitochondrial systems, evidence accumulated that nonenzymic ADP-ribosylation is involved. The following observations support this interpretation ... 

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