Halogen-Free Flame Retarded Rigid Polyurethane Foam: The Influence of Titanium Dioxide Modified Expandable Graphite and Ammonium Polyphosphate on Flame Retardancy and Thermal Stability

A titanium dioxide modified expendable graphite ([EG.sub.T]) was prepared and characterized. The synergistic effect between [EG.sub.T] and ammonium polyphosphate (APP) on the combustion characteristics and thermal stability of rigid Polyurethane foam (RPUF) were investigated through limiting oxygen index (LOI), vertical-combustion, microscale combustion calorimeter tests, and thermogravimetric/differential thermal gravimetric (TG/DTG) analysis. Results showed that [EG.sub.T] modified RPUF presented better thermal stability and flame retardancy than the normal expandable graphite (EG) modified RPUF. Addition of [EG.sub.T] improved the LOI value of 80RPUF/20[EG.sub.T] from 19.0% to 26.9%. Furthermore, the combination of [EG.sub.T] and APP caused the 80RPUF/10APP/10[EG.sub.T] to exhibit a LOI value of 27.8%, a vertical burning level of V-0 and a total heat release of 16.5 kJ [g.sup.-1]. The research gave a body of evidence for synergistic performance between [EG.sub.T] and APP, and the effect of condensed phase mechanism was believed to be the main reason for such synergistic effect. POLYM. ENG. SCI., 58:2008-2018, 2018.
INTRODUCTIONRigid polyurethane foam (RPUF) is extensively used as structural and insulating material and space filling material due to its excellent properties such as low thermal conductivity, high compressive strength, low [...]