Enhanced Thermal Stability and Flame-Retardant Properties of Cross-Linked Polymer Nanocomposites

Polymeric materials have wide applications in the home and industry, providing inexpensive, lightweight, and high performance materials. However, due to the fuel-rich chemical composition of polymers, many flame-retardant additives have been developed to mitigate damages in the event of a fire. Unfortunately, some of these flame-retardants are either toxic or pose significant environmental impacts, highlighting the need for new, nontoxic and environmentally benign polymeric flame-retardants. One promising flame-retardant technology to fill this role is the polymeric nanocomposite. Firstly, the work in this dissertation aims to use thermogravimetric analysis to uncover understudied nanofillers and provide insight into new flame-retardant polymer additives. Secondly, this work aims to investigate methods to enhance the char yield and thermal stability of existing polymer nanocomposites. Nanocomposites containing -zirconium phosphate and poly(methyl methacrylate) were produced by solution casting. These high loading materials (0-30wt% nanofiller) retained their optical transparency, while scattering and absorbing significant amounts of UV light. The nanocomposites were largely noncombustible, with significant residuals even at very high temperatures. Lastly, α-zirconium phosphate nanocomposites had enhanced thermal stability, shown as reduced peak mass loss rates and higher activation energy for thermal decomposition. These studies provide insight into the unique properties of α-zirconium phosphate as a polymeric additive. Aside from studying new nanofillers, the work in this dissertation aims to improve the performance of existing flame-retardant polymer nanocomposites. Poly(methyl methacrylate) nanocomposites containing montmorillonite, aluminum oxide, or silica nanofiller were cross-linked with trimethylolpropane triacrylate to study the interaction between polymer cross-linkages and nanofiller content. In all cross-linked nanocomposites observed, there were synergistic enhancements to the thermal stability of poly(methyl methacrylate), observed as an increase to the onset of degradation by nearly 100⁰C and an increase to the activation energy of degradation. In addition, cross-linked nanocomposites showed synergistic enhancements to char yields. Silica specially surface treated with KH570 was also used to directly cross-link poly(methyl methacrylate), but the degree of cross-linking was low and the effects were less pronounced compared to other cross-linked nanocomposites. This work shows that the combination of nanofiller additives and polymer cross-linking agents provides viable improvement to existing nanocomposites