Flame retardancy of polymers

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This paper was published in Polymer Chemistry  Journal, online 19 Jan 2016

Abstract

Inherent flame-retardant semi-aromatic polyesters, containing special aryl ether and/or ketone structure (“Ar-CO-Ar”, “Ar-O-Ar”, “Ar-O-Ar-O-Ar” or “Ar-O-Ar-CO-Ar-O-Ar”) were synthesized successfully. Interestingly, these polyesters show different flame retardance beyond our traditional knowledge that more benzene rings are beneficial to flame retardance. The polyester containing “Ar-O-Ar-O-Ar” shows excellent flame retardance, whose LOI value reaches 34.1 % and UL-94 rating is V-0. Meanwhile, the polyester with “Ar-O-Ar-CO-Ar-O-Ar” structure does not perform expectedly well (31.6 % and V-2 rating respectively). In order to make clear of the effect of aryl ether and/or ketone structure units on the flame retardance, the pyrolysis behaviours and the char residue are investigated by Py-GC/MS, TGA, and SEM. In TGA test, the char residues of polyesters containing “Ar-CO-Ar”, “Ar-O-Ar” “Ar-O-Ar-O-Ar” or “Ar-O-Ar-CO-Ar-O-Ar” are 31.6%, 22.5%, 30.6%, 38.7%, respectively. These values do not match with the calculated results, which indicate that some special reactions occur during the combustion. Furthermore, these polyesters show a common initial pyrolysis pathway and subsequent unique processes in Py-GC/MS test. Their pyrolysis intermediate products can bind small-molecule free radicals, and eventually form different conjugated aromatic structures. In this way, inherent flame-retardant polyesters are obtained even without any traditional flame-retardant elements. And their flame retardant performance has great relationship with the amount of char formation, the microstructure of char, and the chemical structure of pyrolysis products.

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An interesting article published in ERFA newsletter, page 6:

Fire protection is essential to our daily life. Industrialized countries often value this lightly until the consequences of a serious fire incident affect local populations. With the increasing amount of globally sourced synthetic products on the market (often consisting of or containing flammable substances), it is essential that public authorities ensure that relevant fire safety standards, codes and regulations are maintained, regularly reviewed and strengthened in order to alleviate distressing fire injuries, loss of life and property.

Every day, the general public will routinely use one or more utilities that pose a fire risk: buildings, transport, electrical goods and furnishings, many of which require the addition of flame retardants to meet stringent fire protection standards; they are well-recognized as an essential tool in safeguarding fire safety.

There are several major independent organizations that develop standards, and are classified by their role, position and extent of their influence on local, national, regional (EU) and international standardization arena (CENELEC, CEN, ASME, ASTM)….Read more: Click here

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