Disulfides – Effective radical generators for flame retardancy of polypropylene

Weronika Pawelec, Anton Holappa, Teija Tirri, Melanie Aubert, Holger Hoppe, Rudolf Pfaendner, Carl-Eric Wilen

    Research output: Contribution to journalArticleScientificpeer-review

    22 Citations (Scopus)

    Abstract

    The potential of thirteen aliphatic, aromatic, thiuram and heterocyclic substituted organic disulfide derivatives of the general formula R–S–S–R′ as a new group of halogen-free flame retardants (FR) for polypropylene films have been investigated. According to DIN 4102-1 standard ignitibility test, for the first time it has been demonstrated that many of the disulfides alone can effectively provide flame retardancy and self-extinguishing properties to polypropylene (PP) films at already very low concentrations of 0.5 wt%. In an effort to elucidate the mechanism of the thermal decomposition of disulfide derivatives the fragmentation patterns of the evolved gases from a thermogravimetric analyzer (TGA) have been analyzed by simultaneous mass spectrometry (MS) and Fourier transform infrared spectrometry (FTIR). The main decomposition products initiated by homolytic scission of the S–S bond and/or scission of the C–S bond were identified as thiols, aliphatic and aromatic hydrocarbons, isothiocyanates (depending on the disulfide structures) with further evolution of elemental sulfur and sulfur dioxide at temperatures of above 300 °C and 450 °C, respectively. Based on this preliminary study, we have shown that disulfides represented by e.g. diphenyl disulfide (1), 5,5′-dithiobis(2-nitrobenzoic acid) (2), bis(1-phenyl-1H-tetrazol-5yl)-disulfide (4), 2-bisbenzothiazole-2,2′-disulfide (6) and N,N-dithiobis-(phtalimide) (10) constitute a new halogen-free family of additives for flame retarding of polypropylene.
    Original languageUndefined/Unknown
    Pages (from-to)447–456
    JournalPolymer Degradation and Stability
    Volume110
    DOIs
    Publication statusPublished - 2014
    MoE publication typeA1 Journal article-refereed

    Keywords

    • Disulfides
    • Radical generators
    • Flame retardants
    • Polymer additives
    • polypropylene

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