Abstract
One of the effective ways to enhance flame retardance of polyacrylonitrile (PAN) is through a reactive route, primarily developed in our laboratories, which involved chemical modification reactions utilising phosphorus-containing comonomers. In the present study, diethyl(acryloyloxymethyl)phosphonate (DEAMP) and diethyl(1-acryloyloxyethyl)phosphonate (DE1AEP) were synthesised and copolymerised with acrylonitrile (AN), under radical initiation in an inert atmosphere, in aqueous slurries. The thermal degradation and combustion characteristics as well as the extent of flame retardation were mainly assessed with the aid of various thermo-analytical and calorimetric techniques. It was found that the incorporation of phosphonate groups in polymeric chains of PAN resulted in improved flame-retardant characteristics. Furthermore, it was observed that the actual chemical environment of the phosphorus atom in the acrylic phosphonate modifying groups has little effect on the overall thermal degradation and combustion behaviours of the modified PAN systems. It was also observed that the predominant mode of flame retardance occurred in the condensed phase.
Highlights
Synthetic fibres encompass a wide variety of polymeric materials including polyolefins, acrylics, polyamides and polyesters
We have previously reported on the improved flame retardance of AN-based polymers chemically modified with phosphorylamino and acrylic phosphate groups [8,10]
The choice of DEAMP and DE1AEP as free-radically polymerisable comonomers was governed by the following factors: (a) synthetic procedures are fairly straightforward, providing relatively high yields of the final products: around 80 wt %; (b) ease of availability and modest costs of the reactants; (c) reasonably high hydrolytic stability of phosphonates; (d) relatively high reactivity in copolymerisation reactions
Summary
Synthetic fibres encompass a wide variety of polymeric materials including polyolefins, acrylics, polyamides and polyesters. Staple fibres based on PAN, being soft and resilient, are often used as substitutes or diluents for wool, and fabrics made from them often demonstrate good crease resistance and retention. Owing to their relatively high melting point (which often is accompanied by degradation) and significant carbon yields, PAN fibres are considered to be the most suitable precursors of high-performance carbon fibres [1]. Similar to other organic polymeric materials, once heated the synthetic polymers will undergo various thermal and thermo-oxidative degradation processes that depend on the chemical nature of the fibre and on the intensity of the heat flux [2]. The burning behaviour of fabrics derived from fibrous materials is
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