On the Suitability of Phosphonate-Containing Polyamidoamines as Cotton Flame Retardants

A novel polyamidoamine (M-PCASS) bearing a disulfide group and two phosphonate groups per repeat unit was obtained by reacting N,N’-methylenebisacrylamide with a purposely designed bis-sec-amine monomer, namely tetrae-thyl(((disulfanediylbis(ethane-2,1-diyl))bis(azanediyl))bis(ethane-2,1-diyl))bis(phosphonate) (PCASS). The aim was to ascertain whether the introduction of phosphonate groups, well-known for inducing cotton charring, in the repeat unit of a disulfide-containing PAA increased its al-ready remarkable flame retardant efficacy for cotton. The performance of M-PCASS was evalu-ated by different combustion tests, choosing M-CYSS, a polyamidoamine containing a disulfide group but no phosphonate groups, as a benchmark. In horizontal flame spread tests (HFSTs), M-PCASS was a more effective flame retardant than M-CYSS at lower add-ons with no after-glow. In vertical flame spread tests, the only effect was afterglow suppression with no self-extinguishment even at add-ons higher than in HFSTs. In oxygen-consumption cone calorim-etry tests, M-PCASS decreased the heat release rate peak of cotton by 16%, the CO2 emission by 50% and the smoke release by 83%, leaving a 10% residue to be compared with a negligible resi-due for untreated cotton. Overall, the set of results obtained let envisage that the newly synthe-sized phosphonate-containing PAA M-PCASS may be suitable for specific applications as flame retardant where smoke suppression or reduction of total gas released is a key requirement.