The effects of nano- and molecularly-dispersed additives on the flame retardance in some chain-growth polymers containing covalently bound phosphorus

Unwanted fires in the UK alone cost hundreds of lives (about 600 deaths and 16,000 non-fatal casualties) and about 5.0 billion per year, placing a huge drain on our industry and society. The inhalation of smoke and toxic gases accounted for 50% of the deaths, burns for a further 31%, and a combination of fire-related factors for the remainder. Many of these deaths occurred in fires in which burning polymer-based materials were implicated, either as the primary source of the fire or as a major contributor to the proliferation of the fire. Clearly, the synthesis of polymeric materials that are more flame-retardant has an important part to play in reducing the scale of such deaths in future.The invisible cost through fire safety measures and escalating insurance premiums (estimated as 1% of GDP) is a massive drain on the economy. In addition, in order to address specific threats, such as fire resulting from terrorist action and safety in public buildings, it is essential to develop our understanding of the behaviour of unwanted fires.The overall aim of the project is to prepare poly(methyl methacrylate)s, polystyrenes, polyacrylonitriles and other chain-reaction polymers of commercial significance, reactively modified with phosphorus-containing groups, having physical and mechanical properties not significantly inferior to those of the unmodified counterparts, but with tunable flame-retardance (condensed-phase vs. vapour-phase) to suit them for applications particularly in flame-retardant coatings, textiles, adhesives and thermoplastic moulding materials.We also propose to disperse nanoclays, such as montmorillonite, in polymers reactively modified with phosphorus-containing groups with the aim of retaining the flame retardant moieties longer in the condensed phase during combustion, thus altering the balance between vapour-phase and condensed-phase mechanisms of flame retardation in favour of the condensed phase. A further nanoscopic additive we propose to introduce into our flame-retarded polymers is melamine. Melamine acts as a spumific and can enhance the effectiveness of chars as barriers to combustion. We also intend to explore the effect of introducing cyclodextrins (CDs) into the modified polymers. CDs are cyclic oligomeric sugars and, like cellulose and other polysaccharides, are good char-forming agents. This, we believe, is a novel route which will be systematically explored during the latter part of the programme with a view to identifying the synergistic effects, if any, operating in these composite materials.Finally, detailed information on mechanisms will be obtained from analyses of the gas-phase products of pyrolysis. The results obtained from the study is expected to aid in formulating of novel fire-safe materials on a sound scientific base. This we beleive, in the broader sense, would lead to better ways of flame retarding polymers.