Effect of microencapsulated ammonium polyphosphate on flame retardancy and mechanical properties of wood flour/polypropylene composites

Microencapsulated ammonium polyphosphate (MCAPP) was prepared by using melamine-formaldehyde (MF) resin via polymerization in situ. The product was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, water solubility tests, water contact angle, and thermogravimetric analysis. The tests indicate that ammonium phosphate (APP) was successfully coated by the MF resin, and MCAPP with lower water solubility and higher water resistance outperformed APP. After modification by MCAPP, the flammability of wood-plastic composites (WPCs) was investigated by limiting oxygen index (LOI) and cone calorimetry. The results showed that MCAPP/WPC had higher LOI value, lower heat release rate, and more char residual at the end of cone calorimetry than APP/WPC, indicating that the WPC used MCAPP as flame retardant performed better flame retardancy than the WPC mixed with unmodified APP. Moreover, all measured mechanical properties of MCAPP/WPC were distinctly better than APP/WPC. POLYM. COMPOS., 37:666-673, 2016. (c) 2014 Society of Plastics Engineers