Biodegradable Flame Retardant Nanocomposites

The use of polymers around the world has grown exponentially and is continuing to grow, which makes the production of new and improved polymers a significant priority. Polymers often burn quickly and release a large amount of smoke and heat, and they also drip excessively resulting in further fire propagation. The smoke produced from burning these polymers can contain toxic substances that potentially lead to serious health issues and environmental damage. For these reasons, reducing the propagation of fire is a necessity in polymer development. Along with good flame retardant properties, polymers must also retain decent mechanical properties in order to effectively be applied and utilized. Another important aspect of the development of polymers is sustainability. A substantial number of conventional flame retardant polymers are not biodegradable, and the accumulation of polymer waste can result in detrimental effects on the environment and local ecosystems. Therefore, it is important to discover environmentally-friendly, low-cost, and effective flame retardant additives that can be added to biodegradable polymers to produce an ideal mass-producible polymer.
Polyhydroxyalkanoate (PHA) and Polyhydroxybutyrate (PHB) are biodegradable polymers that have a low cost of production since they are made via microbial synthesis, which is a process that can be manipulated easily. However, these polymers have minimal flame-retardant properties which limit their use in industrial applications. Melamine polyphosphate (MPP), Ammonium polyphosphate (APP), and resorcinol bis (diphenyl phosphate) (RDP) were flame retardant additives that were used in this study, along with graphene to offset the decrease in mechanical properties caused by the addition of the flame retardants. In this study, UL-94 flammability tests, tensile strength tests, and TGA analysis were used to investigate the improvement of PHB by incorporating PHA to promote charring, MPP, and APP to add flame retardancy, and graphene, cellulose, sodium clay, and RDP/RDP clay to improve mechanical strength. A majority of compositions failed the UL-94 flammability test and the few that passed had very weak mechanical properties, however, many insights were made on the effects of the materials used in this study.