Preparation, flame retardancy, and thermal and mechanical properties of polyurethane containing phosphonated bisphenol-A units

A novel phosphonated bisphenol-A glycol (3001-OH) was synthesized by the ring opening reaction between alpha,omega-phenol-terminated aromatic polyphosphonate and propylene oxide. 3001-OH was then incorporated into polyurethanes (PUs) as soft segments, and the effects of 3001-OH on the flame retardancy and thermal and mechanical properties of PUs were investigated. The tensile strength and Young modulus of PUs are improved with the incorporation of 3001-OH into the PUs. With the increase of 3001-OH content in the PUs, the glass transition temperature of the soft segments increases, and the phase separation degree between the hard and soft segments decreases. The limiting oxygen index values of PUs increase from 23.1% to 29.6%, while total heat release values from micro-scale combustion calorimeter decrease from 24.3 to 21.5 kJ g(-1). And the PUs containing phosphorus element successfully met UL-94 V-0 rating requirements. The thermal degradation behaviors and flame retardant mechanism of 3001-OH were studied by thermal gravimetric analysis and pyrolysis gas chromatography/mass spectrometry coupled with the morphology and chemical analysis of the char residues. The results confirm that 3001-OH exerts gaseous-phase and condensed-phase flame retardant effects on the PUs.