Phosphorylation of Kapok Fiber with Phytic Acid for Enhanced Flame Retardancy

Abstract

Kapok fiber (KF), with the characteristics of a natural hollow structure, light weight, and low density, can be used as acoustic and thermal insulation, buoyancy, adsorption, filling, and composite material. The flame-retardant treatment can expand the functionality and application of KF. In this work, the phosphorylation of KF using phytic acid (PA) in the presence of urea at a high temperature was used to enhance its flame retardancy. The phosphorylation reaction conditions were discussed, and the surface topography, thermal degradation, heat release, and combustion properties of phosphorylated KF were studied. The Fourier transform infrared spectroscopy and 31P solid-state nuclear magnetic resonance spectroscopy analyses confirmed the grafting of PA on cellulose by the formation of phosphate ester bonds. Due to the covalent binding of PA, phosphorylated KF exhibited good washing durability. The surface topography, Raman spectroscopy, thermogravimetric (TG), and microcalorimetry analyses revealed the excellent charring ability of phosphorylated KF. In the TG test in nitrogen, the char residue increased to 42.6% of phosphorylated KF from 8.3% of raw KF at 700 °C. In the vertical combustion, raw KF sheet was almost completely burned out within 30 s, while phosphorylated KF was very difficult to catch fire. In the microcalorimetry analysis, the heat release capacity and total heat release of phosphorylated KF decreased to 67 J/g∙K and 3.9 kJ/g, respectively from 237 J/g∙K and 18.1 kJ/g of raw KF. This work suggests that phosphorylated KF is an excellent flame-retardant material.

Development of bacterial cellulose with enhanced flame retardancy and flexibility by phosphorylation with phytic acid and xylitol

“…Figure 1(a) presents a schematic illustration of the production of phosphorylated BC, which was performed according to the method described by Jiang and Tang 28 with certain modifications. In summary, a reaction solution was prepared by dissolving a phytic acid solution with a concentration of 10-40% (o.w.f.)…”

Functional fibers from regenerated wood pulp cellulose and a natural‐based phytate with enhanced flame retardancy properties

“…According to literature, the lower decomposition temperature of the first weight-loss step is associated with the decomposition of PAA into phytic acid prior to the decomposition of cellulose, which favors the occurence of dehydration reactions on the cellulosic substrate, leading to the formation of a protective and stable char layer that prevents the diffusion of combustible gaseous species and heat. 27,54,55 The higher decomposition temperature of the second weight-loss stage, where the rest of the material slowly combusts, is linked to the higher stability of the char formed in the first weight-loss step. 23 Furthermore, the char residue at 800 C increased gradually with the increasing content of PAA, which corroborates the formation of a carbonaceous char that can prevent the depolymerization of cellulose.…”