Three molecules of DOPO were reacted together, in a two-stage process, to give a star-shaped DOPO derivative (GL-3DOPO) containing just over 10% by weight phosphorus. This product showed resistance to thermal composition up to 360°C (considerably higher than DOPO, which begins to decompose at around 200°C), so enabling compatibility with processing temperatures of engineering polymers.
The GL-3DOPO showed good blending compatibility and to be a plasticiser in polar polymers. 25% GL-3DOPO loading enabled achievement of UL94-V0 in PET, PBT, polycarbonate, and polyamines 6 and 66. 8% only GL-3DOPO enabled UL94-V0 in PET, with formation of a compact char layer, suggesting that the molecule acts in both the solid and the gas phase.
“Synthesis of a heat-resistant DOPO derivative and its application as flame-retardant in engineering plastics”, M. Xie et al., J Applied Polymer Science 2017 http://dx.doi.org/10.1002/app.44892