Flame Retardant Mechanism of Silica - Effects of Molecular Weight of Resin
Takashi Kashiwagi, John R. Shields, Richard H. Harris Jr., Rick D. Davis
The effects of resin molecular weight, Mw, on the flame retardant mechanism of silica were studied using two different molecular weights of PMMA, 122,000 g/mol and 996,000 g/mol and two silicas, fused silica with a low surface area and silica gel with a large surface area. A total of six different combined samples were studied having a mass fraction of 10 % silica. The mass loss rate of the six samples in nitrogen and the heat release rate from burning in air were measured at an external radiant flux of 40 kW/m2. The addition of silica gel to the low molecular weight PMMA significantly reduced the mass loss rate and heat release rate; addition to the high molecular weight PMMA provided the largest reductions of these quantities in this study. For fused silica, some reduction in mass loss rate and heat release rate was observed when it was added to the high molecular weight PMMA; addition to the low molecular weight PMMA did not reduce either loss rate. Chemical analysis of the collected residues and observation of the sample surface during gasification reveal the accumulation of silica near the surface; the larger its coverage over the sample surface the more the mass loss rate and heat release rate are. Both the level of accumulation and its surface covereage depend strongly not only on the silica characteristics, but also on the melt viscosity of the PMMA.
, Shields, J.
, Harris, R.
and Davis, R.
Flame Retardant Mechanism of Silica - Effects of Molecular Weight of Resin, Journal of Applied Polymer Science, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=861130
(Accessed December 4, 2023)