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  • 1.
    Kirchhain, Arno
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Yu, Wenbin
    Engman, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Organochalcogen stabilizers efficiently protect model polyolefins exposed to chlorinated media2015In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 118, p. 82-87Article in journal (Refereed)
    Abstract [en]

    The small amounts of chlorine dioxide that are routinely supplemented to drinking water as a disinfectant also cause a degradation of the polyolefin pipes that are used for distribution of the water. Commonly used phenolic antioxidants can extend the service life of the polymer but the expected lifetime is still much shorter than desired (50 years) due to depletion of the antioxidant in the surface zone exposed to the aqueous solution. In search for better stabilizers for the pipes, we have tested an organotellurium compound, 4-(N,N-dimethylamino)phenyl 3-phenoxypropyl telluride (1), as well as its corresponding selenium and sulphur analogues and a series of organotellurium compounds where the electron density at the heteroatom was varied. Stabilizers were dissolved in squalane, which is a liquid hydrocarbon that could serve as a model for a polyolefin. The oxidation induction time (OIT), determined after exposure of the squalane solution to an aqueous solution of 10 ppm of chlorine dioxide for various times was determined by DSC to indicate the loss of antioxidant protection. Whereas Irganox 1010 was only effective as a stabilizer for a few hours, many of the organochalcogen compounds were considerably more resistant (>91 h for compound 1) towards chlorine dioxide.

    Thermogravimetric analyses of antioxidants indicated insignificant decomposition below 200 °C and increasing stability for the lighter chalcogen compounds (telluride < selenide < sulfide). Among organotelluriums, stability increases with increasing electron density at the heteroatom. Oxidation potentials of stabilizers as determined by cyclic voltammetry correlated fairly well with their protective effect in squalane (OIT-values). We therefore hypothesize that these compounds act primarily as electron donors towards peroxyl radicals. As determined by 125Te NMR-spectroscopy, organotellurium compound 1 in the presence of an excess of chlorine dioxide failed to produce an oxidation product. This may be the clue to its long-lasting protective effect in the squalane-assay.

  • 2.
    Shanks, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Al-Maharik, Nawaf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Malmström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Engman, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Eriksson, Petter
    Stenberg, Bengt
    Reitberger, Torbjörn
    Improved Antioxidant Formulations for Polymeric Materials: Synergistic Protective Effects in Combinations of Organotellurium Compounds with Conventional Phenolic Antioxidants or Thiols2003In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 81, no 2, p. 261-271Article in journal (Refereed)
    Abstract [en]

    As judged by differential scanning calorimetry experiments at 190 °C and chemiluminescence measurements at 150 °C, addition of 0.10–0.30 wt.% of certain organotellurium compounds to polypropylene caused a notable protection against oxidation of the material. The best stabilizers (diaryl telluride 3 and alkyl aryl telluride 4), offered a similar degree of protection as commercial stabilizer formulations comprising a mixture of Irganox® 1010 and Irgafos® 168 (0.1 wt.% of each). The protective effect of the organotelluriums was substantially improved in combinations with sterically hindered phenols or thiols. The protection was often much better than the added effects of the individual components and, thus, can be considered as synergistic. Evaluation of a series of stabilizers where tellurium had been exchanged for selenium and sulfur (compounds 2) showed that the synergistic protective effect was unique for tellurium.

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