Abstract
Expandable graphite (EG) and ammonium polyphosphate (APP) were used to improve flame retardancy of rigid polyurethane foams (RPUF). The combustion behaviour of RPUF/EG/APP was investigated by limiting oxygen index (LOI) and cone calorimeter test. The thermal degradation behaviour, the composition and micro-morphology of char were surveyed by TG, X ray photoelectron spectroscopy and scanning electron microscope, respectively.The results show that the optimum ratio of EG and APP is 7:3 and synergistic effect of EG and APP for RPUF is excellent when the addition level of EG/APP is 20%, the LOI reached to 36.0% and the heat release is minimum. In the combustion process of flame retardant RPUF, the smoke and CO suppressant effect of RPUF/EG is outstanding at prophase in spite of loose char layer, the char layer of RPUF/APP is continuous and dense but its thermal stability is insufficient and produced more smoke, and the char layer of RPUF/EG/APP has obviously effect on the insulation heat and has better effect on the inhibition of smoke and CO production. The mechanism of RPUF/EG/APP is related to the increase of thermal oxidation resistance and ratios of N/C and P/C on char surface when polyphosphoric acid permeated EG char layer.
Original language | English |
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Pages (from-to) | 644-649 |
Number of pages | 6 |
Journal | Beijing Ligong Daxue Xuebao/Transaction of Beijing Institute of Technology |
Volume | 34 |
Issue number | 6 |
Publication status | Published - Jun 2014 |
Keywords
- Ammonium polyphosphate
- Expandable graphite
- Flame retardancy
- Rigid polyurethane foam
- Thermal degradation