Sulfur-Based Copolymeric Polyamidoamines as Efficient Flame-Retardants for Cotton

Abstract

The polyamidoamine derived from N,N′-methylenebisacrylamide (M) and glycine (G), M-G, has been shown to be an effective flame-retardant (FR) for cotton in horizontal flame spread tests (HFST), extinguishing the flame at 5% add-on. Its activity was attributed to its intrinsic intumescence. In vertical flame spread tests (VFST), M-G failed to extinguish the flame even at 30% add-on. Conversely, in VFST, the polyamidoamine derived from M and cystine (C), M-C, inhibited cotton combustion at 16% add-on, but in HFST failed to extinguish the flame below 12% add-on. Its activity was ascribed to the release of sulfur-containing volatiles acting as radical scavengers. In this work, the FR effectiveness of M–Gm–Cn copolymers with different G/C ratio was compared with that of the M–G and M–C homopolymers and of M–G/M–C blends of the same compositions. In HFST, both copolymers and blends extinguished the flame. In particular, M–G50–C50 and (M–G/M–C)50/50 extinguished the flame, even at 7% add-on. In VFST, the copolymers with ≥50% M–C units, similar to M–C, inhibited cotton combustion at 16% add-on. At the same add-on, the M–G/M–C blends failed to extinguish the flame. It may be concluded that, in contrast to blends, copolymers combined the merits of both homopolymers in all tests.

Polyamidoamines Derived from Natural α-Amino Acids as Effective Flame Retardants for Cotton

“…The chemical structure of PAAs was assessed by 1 H Nuclear Magnetic Resonance (NMR), collecting spectra in D 2 O at pH 4.0 and 25 • C using a Bruker Advance DPX-400 NMR spectrometer (Milano, Italy) operating at 400. 13 MHz. PAAs and PAA-treated cotton fabrics were analyzed by Attenuated Total Reflectance (ATR) Fourier Transform Infrared Spectroscopy (FT-IR).…”

“…It has long been recognized that intumescence plays a key role in providing FR properties [10]. Subsequently, it was found that the introduction in the polymer chain of disulphide groups, for instance by using L-cystine as monomer [11,12] or comonomer [13], dramatically increased the FR properties. In particular, cotton fabrics treated with disulphide-containing PAAs did extinguish the flame both in horizontal flame spread tests (HFSTs) and more severe, vertical flame spread tests (VFSTs) in the add-on range from 8-12%.…”

The Thermo-Oxidative Behavior of Cotton Coated with an Intumescent Flame Retardant Glycine-Derived Polyamidoamine: A Multi-Technique Study

“…Among α-amino acid-derived PAAs, the glycine-deriving one, M-GLY, was one of the most efficient in imparting self-extinguishment to cotton in HFSTs and, in oxygen-consumption cone calorimetry tests, significantly increased the resistance to an irradiative heat flux of 35 kWm −2 [7]. Moreover, the glycine/L-cystine copolymers, coded M-G-C, also effectively extinguished the flame both in HFSTs and VFSTs [10].…”

“…Under these conditions, the reaction is highly selective since, in addition to the primor sec-amines, only the thiol and phosphine groups can give 1,4-conjugate addition with acrylamides. Many PAAs, besides showing remarkable potential as IFRs for cotton fabrics [7][8][9][10][11], are biocompatible and, therefore, have been extensively studied for biotechnological applications [6,12,13]. In particular, several PAAs derived from natural α-amino acids were found to be non-flammable by applying a butane flame: intumescence occurred on their surface, which swelled and blackened, while the interior remained apparently unaltered.…”

Highlight on the Mechanism of Linear Polyamidoamine Degradation in Water

“…Both PAAs and PAACs are endowed with remarkable potential for biomedical and biotechnological applications [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. More recently, several PAAs and PAACs have proven to be excellent flame-retardants for cotton [ 19 , 20 , 21 , 22 ]. Other applications include, among others, coatings for sensors [ 23 , 24 , 25 ] and heavy metal ion sorbents [ 26 , 27 , 28 , 29 ].…”