Solid state 13C and in situ 1H NMR study on the effect of melamine on the thermal degradation of a flexible polyurethane foam

Abstract

The aim of this investigation is to ascertain whether the mode of action of melamine in exible polyurethane (PU) involves condensed phase chemistry in terms of promoting char formation. A combination of in situ 1 H NMR analysis, solid state 13 C NMR characterization of chars prepared ex situ, and normal TGA and DSC has been employed. Solid state 13 C NMR indicates that there is no major discernible difference in the structure of the dichloromethane-insoluble chars prepared with and without melamine, the remaining polyol only accounting for 20±25 % of the total carbon at 350°C, but still being quite mobile. However, in situ 1 H NMR provides de®nitive evidence that melamine acts in the condensed phase in terms of promoting the formation of rigid char which forms in more signi®cant quantity by 450°C. No increase in the residue yields is observed by TGA upon melamine addition, probably due to a combination of the small sample size and open sample holder in relation to the in situ 1 H NMR analysis which also involves fairly slow heating.

The piloted transition to flaming in smoldering fire retarded and non‐fire retarded polyurethane foam

“…Bastin et al suggested that the synergistic effect is that the TDCPP generates phosphoric acid, which promotes the conversion of melamine into thermally stable network structures such as melam, melem, and melone [24]. Dick et al used 1 H NMR spectroscopy to find that the melamine additive acts in the condensed phase by promoting the formation of a rigid char at temperatures above 400ºC [25]. Melamine is also believed to act as a heat sink, and the nitrogen content of melamine may partly end up as nitrogen gas, providing a heat sink and diluent in the gas phase [26].…”

Synergistic effects of hydroxides and dimethyl methylphosphonate on rigid halogen‐free and flame‐retarding polyurethane foams

“…Owing to emission of toxic and dense smoke, the use of halogen flame retardants is limited. As a result, halogen‐free flame retardants such as ammonium polyphosphate,2–4 expandable graphite,5–10 and melamine11–15 are used in the flexible polyurethane foams. In fact, inorganic hydroxide fillers have replaced halogen flame retardants in many plastic applications due to benefits such as low cost as well as minimal corrosiveness relative to the antimony‐halogen systems and phosphorus‐containing fire retardants.…”

Synergistic Flame Retardant Effects of Expandable Graphite and Ammonium Polyphosphate in Water-Blow Polyurethane Foam

“…ermogravimetric analysis (TGA) is widely used to evaluate the thermal stability of polyurethane [33][34][35][36]. TG and DTG curves of SPUF composites with different flame retardants under nitrogen atmosphere are presented in Figure 1.…”