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Disulfides - effective radical generators for flame retardancy of polypropylene

 
: Pawelec, W.; Holappa, A.; Tirri, T.; Aubert, M.; Hoppe, H.; Pfaendner, R.; Wilén, C.-E.

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Polymer degradation and stability 110 (2014), S.447-456
ISSN: 0141-3910
Englisch
Zeitschriftenaufsatz
Fraunhofer LBF ()

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.

: http://publica.fraunhofer.de/dokumente/N-351819.html