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The fire performance of polyamide 6 (PA6) blended with phenyl phosphonic acid functionalized halloysite nanotubes (PPA-HNTs) is evaluated in order to determine if there is any fire performance gains over the unmodified composite. In the continuing search for safe halogen-free fire retardants for polymers, and the desire to more fully capture the advantages of nano-materials, this research seeks to utilize any synergy which might result in improved fire performance of PA6, via the known advantages offered by nano particles and phosphorus-based compounds. HNTs offer the ability for functionalization by exchange at their hydroxyl sites, while PPA can readily attach at these sites because of its acidity. In this context, the nanotubes act as a carrier for the acid within the polyamide polymeric matrix because it is readily intercalated and functionalized with the acid. The intercalated nano particles are added to the polyamide via melt extrusion and then analyzed using thermal analysis and cone calorimetry. The key finding from this work is that functionalization of HNTs with PPA, followed by blending into PA6 results in a significant improvement in fire performance by altering the combustion dynamics of the polymer. This work proposes a new synergistic fire retardant system for polyamides utilising relatively safe and inexpensive components. More broadly, the concept of using a carrier such as HNTs, which is so easily functionalized, can be applied to other thermoplastic materials, and other additives, for improvements in material properties other than fire.

A collaborative Australian national project funded jointly by the Commonwealth Scientific and Industrial Research Organisation and the Forest & Wood Products Research and Development Corporation has been undertaken to develop a Ôproof of conceptÕ for a combined fire retardant/wood preservative treatment technology for P. radiata to satisfy the requirements of both the Australian Bushfire and Wood Preservation Standards. The focus of the work was on products that found use in exposed outdoor, above-ground applications. This paper reviews the literature currently available regarding the impregnation of wood with chemical systems that offer resistance to both fire and biodegradation and are also suitable for exterior applications. We have found that in general, researchers have chosen to utilise the dual functionality of boron compounds to achieve both fire retardancy and wood preservation. Often, such systems are applied in multi-step processes, which involve an impregnation step followed by a curing step. Because of the leaching problems associated with boron, a great deal of effort has gone into the development of systems which fix the boron into wood so that its preservation properties can be maintained throughout the useful life of the material.

SUMMARYIn this work, we co-formulated an oil-borne copper naphthenate/permethrin wood preservative system with synthetic polymer-based fire-retardant additives prior to the impregnation of Pinus radiata sapwood. We evaluated what effect, if any, the preservative had upon the fire performance properties of the fire retardants and whether the fire retardants impacted on the fungicidal and termiticidal efficacy of the preservative. The fire retardants included halogenated and phosphorus-based systems. A mass loss calorimeter, in conjunction with a thermopile, was used to measure the time to ignition and the peak heat release rate (PHRR) from which the fire performance index (FPI) was determined. The preservative properties were evaluated using termite and soil-block decay bioassays. In summary, we found that the rate of fire growth was reduced when the fire retardants were used in combination with the wood preservative. We also found that the PHRR was a better determinant of fire performance than the FPI. The performance of the wood preservative was enhanced against fungal decay and termite attack when used in combination with the fire retardants. The fire retardants also demonstrated some wood preservative properties of their own.