Abstract
In this work, a novel intumescent flame retardant (IFR) system was fabricated by the introduction of chitin as a green charring agent, ammonium polyphosphate (APP) as the acid source, and melamine (MEL) as the gas source. The obtained chitin-based IFR was then incorporated into a polylactic acid (PLA) matrix using melt compounding. The fire resistance of PLA/chitin composites was investigated via the limiting oxygen index (LOI), UL-94 vertical burning, and cone calorimeter (CONE) tests. The results demonstrated that the combination of 10%APP, 5%chitin and 5%MEL could result in a 26.0% LOI, a V-0 rating after UL and a 51.2% reduction in the peak heat release rate during the CONE test. Based on the mechanism analysis from both the morphology and the chemical structure of the char, it was suggested that chitin was a promising candidate as a charring agent for chitin reacted with APP and MEL with the formation of an intumescent layer on the surface.
Highlights
Polymers 2021, 13, 3513. https://Considering the serious energy crisis, traditional plastics that are synthesized through petroleum-based resources are gradually being replaced by bio-based and biodegradable materials [1]
Different kinds of flame retardants, including intumescent flame retardants (IFRs), hypophosphites, phytates, metal oxides, nano-particles, and graphite structures, have all been incorporated into polylactic acid (PLA) matrixes to solve this problem [5,6,7,8,9,10,11]
IFRs, which consist of an acid source (ammonium polyphosphate (APP)), a charring agent (pentaerythritol (PER)), and a blowing agent (melamine (MEL)), have attracted increasing attention due to their halogen-free and high efficiency characteristics [12]
Summary
Considering the serious energy crisis, traditional plastics that are synthesized through petroleum-based resources are gradually being replaced by bio-based and biodegradable materials [1]. Cellulose [15], β-cyclodextrin [16], starch [17], and polypseudorotaxan [18] have all been applied as a charring agent in PLA/IFR composites to improve the fire resistance of PLA and maintain its environmental friendliness at the same time. It was expected that chitin could act as a charring agent, which takes effect in the condensed phase through the formation of intumescent char layers, improving the fire resistance of the polymeric material. The flame retardancy, thermal stability, and mechanical properties of the PLA/chitin composites were investigated and the flame-retardant mechanism was proposed
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