Effect of trimethylolpropane triacrylate cross-linkages on the thermal stability and char yield of poly (methyl methacrylate) nanocomposites

Using an in-situ polymerization method, poly (methyl methacrylate) (PMMA) cross-linked by trimethylolpropane triacrylate (TMPTA) was embedded with nanosilica, aluminum oxide, or modified montmorillonite to produce various cross-linked nanocomposites. The same three nanofillers were also embedded into PMMA without TMPTA cross-linkages to quantify the effect of TMPTA cross-linkages on the thermal stability and char yield of nanocomposites. Data from Thermogravimetric Analysis (TGA) and Derivative ThermOgravimetric Analysis (DTG) were used to show that cross-linking and nanofiller content act synergistically to improve the thermal stability of PMMA, increasing the on-set of degradation by nearly 100 degrees C. The increase in thermal stability was attributed to the elimination of low temperature end initiated polymer unzipping by TMPTA cross linkages and simultaneous stabilization of remaining degradation reactions due to nanofiller content. Char formed during a fire accumulates on the surface of the nanocomposite, forming a barrier that protects any unburned material below the surface. The DTG data showed nanocomposites Containing 1 wt% silica in PMMA cross-linked by TMPTA produced 14.1% char residues, while nanocomposites without TMPTA cross-linkages required five times the mass of nanofiller to achieve similar yields.