Influence of ammonium polyphosphate-/poly(acrylic acid)-based layer by layer architectures on the char formation in cotton, polyester and their blends

Ammonium polyphosphate and poly(acrylic acid) have been chosen to build a complex, four-layered (or quadlayered) hybrid organic-inorganic architecture exploiting the Layer by Layer assembly, in order to promote the formation of an aromatic and stable carbonaceous structure (char), able to thermally protect cotton, polyester and their blends. To this aim, a different number of quadlayers (namely, 1, 5 and 10) consisting of poly(diallydimethylammonium chloride)/poly(acrylic acid)/poly(diallydimethylammonium chloride)/ammonium polyphosphate have been deposited on the chosen fabrics and investigated. Thermogravimetric analysis coupled to isothermal tests performed in a gravity convection oven at fixed temperatures has shown that the presence of such architectures is able to enhance the char formation in a remarkable way. Furthermore, infrared spectroscopy has pointed out the aromatic nature of the residues left by the treated fabrics upon heating at high temperatures, regardless of the quadlayer number and the fabric type.