Fabrication and characterization of waterborne polyurethane (WPU) with aluminum trihydroxide (ATH) and mica as flame retardants

Flame-retardant polymer composites with specific, finely dispersed fillers were obtained using eco-friendly water-based polyurethane adhesives for coatings on wood panels and were composed of waterborne polyurethane (WPU), aluminum trihydroxide (ATH) and mica. WPU was synthesized from the polycondensation of isophorone diisocyanate (IPDI), polyethylene glycol (PEG), poly(propylene glycol) (PPG), ethylenediamine (EDA), 2,2′-bis(hydroxymethyl)-propionic acid (DMPA) and triethylamine (TEA). These composites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), flammability testing, environmental testing and impact resistance testing. It was shown that the WPU can serve as an effective dispersant that blends with ATH and mica not only improving the dispensability properties but also enhancing the flame retardant properties. For example, the thermal decomposition temperature for a 5 % weight loss (T_{d 5%}) reached 325 °C when the hybrid flame retardants were comprised of 10 g WPU and 100 g ATH/mica in a 15/85 ratio (10 WPU/15 ATH/85 mica). In comparison, with pure WPU, the thermal decomposition temperature for a 5 % weight loss (T_{d 5%}) was only 255 °C. In addition, the fire retardant grade for flame retardant composites comprised of 10 WPU/15 ATH/85 mica (10/15/85 weight ratio) and wood panel reached level 2 in accordance with CNS 14705 (Chinese National Standard 14705).