The Effect of Cellulose Fibre Length on the Efficiency of an Intumescent Flame Retardant System in Poly(lactic acid)

Abstract

In the flame retardancy of the biopolymer matrix and natural fibre reinforcement containing green composites, researchers face multiple challenges, such as low thermal stability, the candlewick effect of fibres and compatibility issues. Cellulosic fibres have been shown to have char-promoting properties and to advantageously interact with intumescent systems. In this work, melamine-polyphosphate was combined with neat or flame-retardant-treated cellulosic fibres differing in fibre length to obtain intumescent flame retarded poly(lactic acid) composites. The effect of the cellulose fibre length was evaluated in both forms. The structure-property relationships were evaluated by thermal and flammability test methods. It was found that the formation and the structure of the fire-protecting char are influenced by the length of the cellulose fibres, and thus it noticeably affects the effectiveness of the flame-retardant system. Cellulose fibres with an average length of 30–60 µm were found to contribute the best to the formation of an integrated fibrous-intumescent char structure with enhanced barrier characteristics.