Feedstock Recycling of Flame-Resisting Poly(lactic acid)/Aluminum Hydroxide Composite to l,l-lactide

To achieve the chemical recycling of flame-resisting materials consisting of poly(l-lactic acid) (PLLA), a safer flame-resisting material, PLLA/aluminum hydroxide {Al(OH)3} composite, was investigated the capability of the feedstock recyclability to optically active monomer l,l-lactide. The thermal stabilization of the composite was improved compared to those of as-polymerized PLLA and Al(OH)3 themselves, which makes the melt processing of the composite easier. Nevertheless, at temperatures lower than 300 °C the effective depolymerization of PLLA proceeded, without any racemization reaction, to selectively convert into l,l-lactide, with Al(OH)3 acting as a catalyst for the depolymerization. This means that the PLLA/Al(OH)3 composite is capable of reconciling flame resistance with feedstock recycling of PLLA to cyclic monomer.