1 Synthesis and Thermal Analytical Screening of Metal Complexes as Potential Novel Fire Retardants in Polyamide 6.6 Alistair F. Holdsworth 1a , A. Richard Horrocks 1b and Baljinder K. Kandola 1 Affiliations: 1) – School of Engineering, University of Bolton, Deane Road, Bolton, BL3 5AB, UK, a) Now at School of Physical Sciences and Computing, University of Central Lancashire, Preston, UK b) Corresponding Author Abstract The development of new flame retardants is of ever increasing importance because of ecotoxicity concerns over existing systems and related regulatory pressures. From a range of low-toxicity, water-insoluble reagents, a total of 151 metal complexes were assessed for their potential to impart flame retardant behaviour in polymer matrices. These were successfully synthesised on a small scale and possible interactions were explored with a model engineering polymer, namely polyamide 6.6 (PA66). Powder mixtures of each complex with PA66 in a 1:3 mass ratio were analysed under air using TGA/DTA. Based on the stability of each at the typical processing temperature of 290 o C and its char forming potential (the final residue requirement at 580 o C being > 25%), selected mixtures were then analysed further using a differential mass loss technique. Metal complex/PA66 mixtures in which the differential residual mass at 470 o C was > 10% with respect to the theoretical value were considered to have a positive char forming interaction. Only eight of the metal complexes passed this last criterion including aluminium, tin (II) and zinc tungstates, three tin (II) phosphorus oxyanion complexes, iron (II) aluminate and iron (III) hypophosphite. These selected compounds were synthesised on a larger scale (c.a. 100 g), characterised and compounded into PA66 at 5 wt% for flammability assessment using LOI, UL94 and cone calorimetry. Of these, only aluminium tungstate and iron (II) aluminate showed some degree of FR behaviour with LOI values ≥ 23.0 vol% compared with PA66 (LOI = 22.9 vol%) and the former almost achieved a UL94 V-2 rating. However, while up to 32% reductions in total heat releases and up to 49% reduction in PHRR in cone calorimetric tests were observed for the metal complex/PA66 composites generally, those for Al2(WO4)3 were 6 and 29% respectively and for Fe(AlO2)2 were 18 and 45% respectively Keywords: metal complex, synthesis, polyamide 6.6, thermal analysis, char promotion, flammability 1.0 Introduction The fire hazard posed by many polymeric materials often necessitates the incorporation of flame retardant compounds in order to meet stringent regulatory factors which increase safety with respect to ignition resistance or burning intensity. 1, 2 Recently, the replacement of potentially toxic flame retardant compounds and synergists such as certain monomeric polybrominated flame retardant/antimony trioxide