Effect of cellulose whisker and ammonium polyphosphate on thermal properties and flammability performance of rigid polyurethane foam

Cellulose whisker (CW) is employed as a novel carbonization agent to build green and efficient intumescent flame retardant (CWAPP) with ammonium polyphosphate (APP). Due to the presence of CW, CWAPP exhibits more excellent flame retardancy compared with APP in rigid polyurethane foam (PU). PU-added CWAPP (PU/CWAPP) obtains higher LOI value than that with the same loading of APP. Results also indicate that CWAPP have better water resistance compared with APP in PU. Flame-retardant property of PU/APP is decreased remarkably after soaked in hot water. By comparison, that of PU/CWAPP is rarely changed after the same treatment. CWAPP also shows a positive effect on the mechanical property in PU, and compression strength of PU/CWAPP is higher than that of PU/APP with the same content of flame retardant.