Synergistic effect between ammonium polyphosphate-functionalized poly(lactic acid) and phosphated avocado seed on the flame-retardant properties of poly(lactic acid)/ethylene–vinyl acetate copolymer composites

Composites of modified avocado seed with ammonium polyphosphate (APP)-functionalized poly(lactic acid) (PLA), in a PLA/ethylene–vinyl acetate copolymer (EVA) matrix, were prepared in an internal mixer and characterized. The results of flame retardancy tests show that the joint use of APP and modified avocado seeds in the polymer mixture can provide flame-retardant characteristics. We observed a decrease in the heat release peak and in the total energy released, in addition to the generation of a residual intumescent layer after cone calorimeter tests. On the other hand, APP-functionalized PLA and avocado seed in concentrations of 10% and 30% (by weight), respectively, have a synergistic effect when incorporated into the polymer mixture; reducing the peak of the heat release rate (pHRR) by 58% and the total energy released by 34%, resulting in an amount of waste of about 18%. In the same way, this synergistic effect allowed the material to be classified as V-0 in the UL-94 tests as well as achieving LOI values of 30%. The results show that this combination can be classified as a self-extinguishing material. Therefore, this research aims to promote the use of more sustainable and renewable feedstocks to produce flame retardants in polymeric materials.

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