Preparation of a chitosan‐based flame‐retardant synergist and its application in flame‐retardant polypropylene

Abstract

A novel flame-retardant synergist, chitosan/urea compound based phosphonic acid melamine salt (HUMCS), was synthesized and characterized by Fourier transform infrared spectroscopy and 31 P-NMR. Subsequently, HUMCS was added to a fireretardant polypropylene (PP) compound containing an intumescent flame-retardant (IFR) system to improve its flame-retardant properties. The PP/IFR/HUMCS composites were characterized by limiting oxygen index (LOI) tests, vertical burning tests (UL-94 tests), microscale combustion calorimetry tests, and thermogravimetric analysis to study the combustion behavior and thermal stability. The addition of 3 wt % HUMCS increased the LOI from 31.4 to 33.0. The addition of HUMCS at a low additive amount reduced the peak heat-release rate, total heat release, and heat-release capacity obviously. Furthermore, scanning electron micrographs of char residues revealed that HUMCS could prevent the IFR-PP composites from forming a dense and compact multicell char, which could effectively protect the substrate material from combusting.

An Overview on the Use of Lignin and Its Derivatives in Fire Retardant Polymer Systems

“…Few studies proposed to replace the acid source by bio-based component: more specifically, fumaric acid and phytic acid were proposed as suitable candidates to develop intumescent system with PLA [70]. Bio-based carbonizing agents such as starch [71], cyclodextrin [72] and chitosan [73] have been proposed and showed high efficiency. Among those entirely bio-based carbonizing agents, lignin has also been considered by some researchers due to its abundance in nature and high charring capacity.…”

“…In this context efforts have been extended, especially from the last 10 years, to use different eco-friendly bio-based extracted plant resources and other natural resources due to the desire to promote a "green concept". Thus, the formulation of intumescent flame retardant (IFR) systems may be based on bio-based acidic source such as phytic acid [87], metallic phytates [64], different bio-based carbonization agents like chitosan [73], cyclodextrin [72] and starch [71] exploiting melt blending processes. Among bio-based carbonizing agents, lignin has also been considered as an effective char former due to its highly aromatic structure.…”

Advances in Halogen-Free Flame Retardants

“…They provide very robust fire safety and flame resistance performance. The carbon agent forms multicellular charred layers, the char may be soft or hard [5]. Soft char IFRs: composed of a carbon source pentaerythritol (PER), acid source (ammonium polyphosphate) and a gas-blowing additive (melamine) harder char IFRs: composed of sodium silicates and graphite.…”

Microstructure, Thermal Conductivity, and Flame Retardancy of Konjac Glucomannan Based Aerogels

“…It has been reported that starch [ 24 ], cellulose [ 25 ], and cyclodextrin (CD) [ 26 ] are natural carbon sources, which can be used to replace conventional materials and form new environmentally friendly intumescent flame retardant systems due to the good charring ability. Furthermore, polysaccharides such as alginate and chitosan have been proved to have good retardant properties, which can significantly improve the limiting oxygen index (LOI) of thermal insulation materials [ 27 , 28 ].…”