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Bio-based polyurethane-polyisocyanurate composites with an intumescent flame retardant

Kurańska, Maria, Cabulis, Ugis, Auguścik, Monika, Prociak, Aleksander, Ryszkowska, Joanna, Kirpluks, Mikelis
Polymer degradation and stability 2016 v.127 pp. 11-19
burning, calorimeters, cameras, combustion, differential thermal analysis, flame retardants, flammability, foams, graphene, graphs, heat, industry, insulating materials, oxygen, polyols, polyurethanes, rapeseed oil, risk, smoke, temperature, thermal stability, thermography, thermogravimetry, vegetables
Rigid polyurethane and polyisocyanurate (PUR-PIR) foams are one of the most effective thermal insulation materials applied in a wide range of industries. A sustainable solution for the production of these materials is to substitute one of their petrochemical components with a component produced from bio-based resources, like vegetable oils.The biggest disadvantage of this type of thermal insulation is its high flammability which usually is reduced by an addition of halogen-based flame retardants. Halogenated flame retardants are getting out of use due to potential health risks. Two different bio-based polyols obtained from rapeseed oil were applied to develop rigid PUR-PIR foams with isocyanate indices of 150 and 250. Flammability of these materials was decreased using an intumescent expandable graphite (EG) filler; 0%; 3%; 6% and 9% contents of EG were used. Flammability (Cone calorimeter), combustion (limited oxygen index, thermal imaging), thermal stability (TGA/DTG) were studied for the developed PUR-PIR foams. The addition of EG did not change the ignition behaviour of the developed materials but it had a significant influence on other flammability properties. Due to the development of a stable char layer, the peak value of the heat release in the Cone Calorimeter test was reduced from 240 to 136 kW/m², the released smoke was also reduced from 560 to 288 m²/m². TGA graphs showed a significant char formation (sample with 9% of EG) that was stable at high temperatures, over 400 °C. The addition of EG to the PUR-PIR system had a positive effect on the burning process which was confirmed by thermal imaging camera results. The formation of the char layer moderated the combustion of the PUR-PIR foams and increased the burning time.