Posted on 11/09/2023 in Fire Safety 2023
Reactive phosphorus PIN FR for poly(lactic acid)

Marie-Odile Augé, Centrale Lille, France
Daniele Roncucci, Empa / ETHZ, Switzerland

The bio-sourced polymer poly(lactic acid) (PLA) is highly flammable and requires flame retardants to reduce fire risks. A new phosphorus PIN flame retardant DDPO (a phosphorus-containing PIN compound, produced by reacting diethyl phosphite with neopentylene glycol) was incorporated into PLA by copolymerisation, in a one-pot reaction with (L)-lactide (the cyclic dimer of lactic acid) and a tin salt catalyst. The objective was to overcome the challenge that phosphorus monomers tend to inhibit polymerisation, including of PLA. Over 90% of lactide was polymerised, but only around 50% of the DDPO monomer was consumed. The resulting copolymer with c. 1% P content, is amorphous compared to neat PLA but showed lower molecular weight and was somewhat gel-like. Peak heat release rate was reduced and delayed. This initial work has so far been carried out at the 1g synthesis scale and UL94 fire performance not yet tested, as this is the initial stage of the research. These polymers could be used as adhesives where fire protection is needed and could be post-functionalized by reactions with the P-H moiety.

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