The flammability of polyacrylonitrile and its copolymers IV. The flame retardant mechanism of ammonium polyphosphate

Zhang, Jun, Horrocks, Richard ORCID: 0000-0003-1431-058X and Hall, M. E. (1994) The flammability of polyacrylonitrile and its copolymers IV. The flame retardant mechanism of ammonium polyphosphate. Fire and Materials, 18 (5). pp. 307-312. ISSN 0308-0501

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Official URL: https://onlinelibrary.wiley.com/journal/10991018

Abstract

Ammonium polyphosphate is shown to be an effective flame retardant for homopolymeric and selected fibre‐forming copolymers of acrylonitrile. Compared with other phosphates and phosphorus‐containing species, it significantly increases both limiting oxygen index and char levels. The mechanism of retardancy is shown to be both physical and chemical in character. When heated to 300°C, the polyphosphate melts and converts to polyphosphoric acid which acts as a physical barrier to surface polymer oxidation and promotes nucleophilic oligomerization of pendant, adjacent nitrile groups. A reduction in the activation energy of this first stage of acrylic polymer degradation suggests that the favoured decomposition route gives rise via oligomerization to char‐promoting precursors. Char analyses indicate an empirical formula of C30H13N7P2, which compares favourably with that of a proposed phosphorylated, polynuclear, aromatic heterocyclic structure.

Item Type: Article
Divisions: University of Bolton Research Centres > Institute for Materials Research and Innovation
Depositing User: Tracey Gill
Date Deposited: 09 Aug 2018 14:16
Last Modified: 09 Aug 2018 14:16
Identification Number: 10.1002/fam.810180506
URI: http://ubir.bolton.ac.uk/id/eprint/1839

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