NMR evaluation of montmorillonite's d-spacings on the formation of phosphocarbonaceous species in intumescent systems

摘要

To further investigate the influence of the d-spacing of montmorillonite types derived from Cloisite Na on the process of the intumescent layer formation, composites of poly(ethylene-co-butylacrylate), EBA-30, with an intumescent formulation consisting of ammonium polyphosphate and pentaerythritol were processed and heated at different temperatures. The residues were analyzed by C-13, P-31, and Al-27 solid-state nuclear magnetic resonance (NMR). C-13 NMR peaks in the aromatic range of 100-150 ppm for samples heated at 350 degrees C suggest that the montmorillonites with smaller d-spacing (13.5 and 21.8 angstrom) accounted for the greater amounts of condensed aromatic structures, leading to the char. For d-spacing of 35 angstrom, the condensation of the polyaromatic structures occurs more slowly, retarding the char formation. The Al-27 NMR peak around -15 ppm for samples heated at 280 degrees C indicates the destruction of montmorillonite structure, producing aluminophosphate species, meaning that the d-spacing influences the reactions under this temperature. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48053.