Impact of Isocyanate Index on Flame Retardancy, Thermal Stability andCombustion Behaviors of Rigid Polyurethane Foam
LIU Hongyin1,2, YANG Hongyu1,2, CHEN Mingfeng2
1 State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044 2 College of Materials Science and Engineering, Chongqing University, Chongqing 400044
Abstract: Aiming at comparatively investigating the impact of isocyanate index (NCO) on flame retardancy, thermal stability and combustion behaviors of rigid polyurethane foam (RPUF) with and without the addition of common flame retardants, a serious of RPUF, rigid polyurethane foam/expandable graphite (RPUF/EG) and rigid polyurethane foam/ammonium polyphosphate (RPUF/APP) samples with different NCO (1.5 and 3) were prepared. The flame retardancy, thermal degradation and combustion behaviors of each sample were investigated. The limit oxygen index (LOI) results indicated that increasing isocyanate index was beneficial to the flame retardancy of all foam systems, specially the LOI data of RPUF/EG presented a substantial growth from 29.5% to 33.5% with the increasing NCO. The results of thermogravimetric analysis (TGA) showed that the increase of NCO can improve the initial decomposition temperature and carbon residue in all samples effectively. The data obtained from cone calorimeter (Cone) revealed that the increase of NCO can significantly reduce the heat release rate (HRR) of RPUF and RPUF/EG. And the rate of mass loss was slowed down, carbon residue increased with the rise of NCO. The findings in this study demonstrated that isocyanate index played an important role in flame retardancy, thermal degradation and combustion behaviors of RPUF, which must be paid more attention to the studies of flame-retardant RPUF.
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2019, Vol. 33 
