Layered double hydroxides (LDH) are clays which are frequently used in a variety of polymer applications as functional additives. These include uses such as PVC heat stabiliser, reinforcing filler, flame retardant and many more. It is well known that the structure, morphology and composition of materials used as additives in polymers are important. The method of synthesis of the synthetic LDH clays affects the structure and final morphology of the material strongly. Several different techniques are being used for the commercial synthesis of LDH as polymer additive. These include the co-precipitation method, the urea hydrolysis method, the mixed oxide/hydroxide method and dissolution-precipitation methods. It is also possible to produce LDH materials with different metal compositions and interlayer ion; using several different synthesis and/or modification techniques. Each of these with different surface and bulk morphologies, physical properties and additive performance. LDH materials containing different metal ions were prepared via different synthesis techniques. These were modified via different intercalation methods and with a selection of anions. All the samples were analysed and characterised. Finally, compounds of the different LDH samples were prepared and tested for flame retardancy in a cone calorimeter. The aim was to identify the contribution of metal composition, anion composition and physical properties on the flame retardant properties of the final composites. Preliminary results indicate that the metal composition of the LHD plays a much larger role in the flame retardant properties of the final composite than the synthesis method. The anion in the interlayer also plays a large role in the performance of the additive as flame retardant.