| 1. |
- Azhdar, Bruska, et al.
(författare)
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A new method for assessing the efficiency of stabilizers in polyolefins exposed to chlorinated water media
- 2009
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Ingår i: Polymer testing. - : Elsevier BV. - 0142-9418 .- 1873-2348. ; 28:6, s. 661-667
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Tidskriftsartikel (refereegranskat)abstract
- The chlorine used as disinfectant in tap water degrades most materials, including polyethylene. The most adequate (functional) test method, the pressure test, is complicated and expensive because the chlorinated aqueous media (Cl-2 or ClO2 in water) are unstable and they undergo reactions that are dependent on the pH. A new method which assesses the protection efficiency of phenolic antioxidants in polyolefins was developed. The method uses a liquid hydrocarbon analogue, squalane, in which antioxidants are dissolved. The organic phase was dispersed in the aqueous chlorinated phase (containing 10 ppm of either Cl-2 or ClO2; pH=6.8) at 70 degrees C by intense stirring. The depletion of antioxidant (Irganox 1010) was monitored by standard DSC determination of the oxidation induction time. It was shown that 300 min of exposure was sufficient to obtain useful data.
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| 2. |
- Carlsson, Magnus, et al.
(författare)
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A comparative study on the degradation of cotton linters induced by carbonate and hydroxyl radicals generated from peroxynitrite
- 2005
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 59:2, s. 132-142
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Tidskriftsartikel (refereegranskat)abstract
- Carbonate (CO3.(-)) and hydroxyl (HO.) radicals were chemically produced in cotton linter suspensions using peroxynitrite as a radical precursor. Both radicals could degrade cotton linters, as shown by viscosity and GPC-SEC measurements. As evidenced by the viscosity measurements, the presence of oxygen during the cotton linter treatments slightly increased cellulose degradation by both radicals. For the carbonate radical, more than 90% of the viscosity losses could be recovered by reductive NaBH4 treatment before measuring the viscosity, whereas only approximately 40% of the viscosity was recovered after hydroxyl radical degradation and subsequent NaBH4 treatment. This indicates that carbonate radicals mainly abstract H-atoms adjacent to hydroxyl groups, i.e., at C-2, C-3 and C-6. This intramolecular selectivity may reflect a polar effect, whereby hydrogen atom abstractions from these positions are favoured. In addition, abstraction at C-6 would be sterically and statistically favoured.
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| 3. |
- Carlsson, Magnus, et al.
(författare)
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The Carbonate Radical as One-Electron Oxidant of Carbohydrates in Alkaline media
- 2005
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 59:2, s. 143-146
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism by which the carbonate radical anion reacts with D-glucose in alkaline aqueous solutions has been studied by means of gamma-radiolysis. From the product analysis it is concluded that the reaction sequence is initiated by a one-electron transfer between the carbonate radical anion and deprotonated D-glucose. In the presence of molecular oxygen, the major, if not only products of this reaction sequence are formic acid, arabinose and gluconic acid and reaction schemes are proposed to account for the observed formation of these products.
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