Flax fibre reinforced PLA/TPS biocomposites flame retarded with multifunctional additive system

Fully biodegradable composites were developed, possessing prominent mechanical performance and reduced flammability at the same time. The manufactured composites consisted of PLA/TPS biopolymer matrices reinforced with chopped flax fibres. The flammability of the prepared biocomposites was reduced by a newly synthesized multifunctional additive system. Glycerol phosphate (GP), a plasticizer of starch with flame retardant potential, and a novel phosphorous-silane (PSil), applied as a surface treating agent of the reinforcing biofibres, were successfully combined in order to reduce the flammability of the prepared biocomposites. Owing to the beneficial effect of the applied multifunctional additive system, a loading of as low as 10 wt% of ammonium polyphosphate (APP) proved to be sufficient to provide prominent levels of flame retardancy to the composites, i.e. V−0 rating according to UL94, 33 vol% LOI and a 40% reduction of heat emission were achieved. Furthermore, the combined application of the surface treated reinforcing flax fibres and plasticizer in the biodegradable, flame retarded biocomposites resulted in well-balanced strength and stiffness.