Interaction of a phosphorus‐based FR, a nanoclay and PA6—Part 1: Interaction of FR and nanoclay

Abstract

SUMMARYThe thermal decomposition of organophosphorus fire-retardant (OP1311) and/ or organonanoclay (Cloisite 30B) is hereby investigated employing thermogravimetric analysis (TGA), to give an insight into their intrinsic behaviour and interaction in polymer nanocomposites for fire safety applications, because the addition of OP1311 and Cloisite 30B in Polyamide 6 (PA6) seems to have a synergistic effect on the thermal decomposition of PA6 (part 2 of the paper). An important objective of this research was to determine to what extent phosphorus components escape in the gaseous phase, which will affect the heat of combustion of the fire-retarded polymer. The decomposition products arising from pyrolysis and combustion are investigated by means of Fourier transform infrared spectroscopy. Under pyrolytic conditions, the inclusion of Cloisite 30B into OP1311 (FR) shows a synergistic effect on the initial mass loss at low temperature of ∼ 280-420 • C and leads to the acceleration of the thermal degradation process. While the DTG curve of Cloisite 30B shows two distinct degradation peaks (steps) that of OP1311 and OP1311 plus Cloisite 30B show four degradation steps. TGA measurements of OP1311 in nitrogen show more mass loss than in air, whereas Cloisite 30B gives similar amounts of mass loss in air and nitrogen. In nitrogen, the major evolved gaseous species from Cloisite 30B alone are hydrocarbons, 2-(diethylamino)ethanol and water, whereas the evolved gases from that of OP1311 at ∼ 320 • C are mainly water, at ∼ 420 • C, carbon dioxide, water and ammonia and at 480-570 • C diethylphosphinic acid. Under thermo-oxidative conditions, the gases evolved are mainly carbon dioxide and water from both Cloisite 30B and OP1311.

Interaction of a phosphorus‐based FR, a nanoclay and PA6. Part 2 interaction of the complete PA6 polymer nanocomposites

“…While, the difference between the TGA curves of PA6+FR and PA6+FR+NC is, however, not significant. It shows that a lot of FR goes to the gas phase as has been detailed in part 1 [11].…”

“…On the other hand, the NC is known to increase char formation and form 'thermal barrier layer' without necessarily increasing the thermal degradation rate (lowering degradation onset temperature). It seems that most of the FR escapes to the gaseous phase (see Part I, [11]). …”

Nanoclay and carbon nanotubes as potential synergists of an organophosphorus flame-retardant in poly(methyl methacrylate)

“…[23,33,34], whereas flame-retarded PMMAs with or without the filler nanoparticles possess additional shoulders around 430e450 C resolved by differential thermogravimetry. These mass loss rate shoulders might be attributed to the evolution of gaseous decomposition products of the organophosphorus flame-retardant [25,26]. Table 4 lists some of the important thermogravimetric data.…”

“…In the former mechanism, transport of oxygen and flammable volatiles are impeded, and polymer is shielded from the external radiant heat and the heat feedback of the flame by the act of the protective intumescent layer. The latter mechanism involves the evolution of flame inhibiting phosphorus species together with less-combustible products like melamine contributing to the gasphase action [25,26].…”

Pyrolysis and flammability behavior of long (Glass fiber)‐Reinforced polyamide 6 by aluminum alkylphosphinate‐based flame retardants in combination with organic montmorillonite

“…According to the acting mechanism of alkylphosphinate‐based flame‐retardant systems, one can imagine that the potential flame‐retardant synergism might exist between aluminum phosphinates and organic montmorillonite (OMMT), because OMMT has been widely used as a flame retardant by the formation of multilayered carbonaceous‐silicate barrier on the polymer surface that will insulate the underlying material from the heat flux of the flame and act as a mass transport barrier . Several studies confirmed this speculation that the alkylphosphinate‐based flame retardant and OMMT did have a synergistic effect on polyamide 6 (PA6) . Ramani et al systematically investigated the interaction of a phosphorus‐based flame retardant, a nanoclay, and PA6 and found that the addition of the phosphorus‐based flame retardant and the nanoclay in PA6 seemed to have a synergistic effect on the thermal decomposition of PA6.…”