Flame retardant properties and mechanism of an efficient intumescent flame retardant PLA composites

Abstract

The charring agent (CNCA-DA) containing triazine and benzene rings was combined with ammonium polyphosphate (APP) to form intumescent flame retardant (IFR), and it was occupied to modify polylactide (PLA). The flame retardant properties and mechanism of flame retardant PLA composites were investigated by the limited oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis, microscale combustion calorimetry, scanning electron microscopy, laser Raman spectroscopy analysis and X-ray photoelectron spectroscopy. The analysis from LOI and UL-94 presented that the IFR was very effective in flame retardancy of PLA. When the weight ratio of APP to CNCA-DA was 3:1, and the IFR loading was 30%, the IFR showed the best effect, and the LOI value reached 45.6%. It was found that when 20 wt% IFR was loaded, the flame retardancy of PLA/IFR still passed UL-94 V-0 rating, and its LOI value reached 32.8%. The microscale combustion calorimetry results showed that PLA/IFR had lower heat release rate, total heat release, and heat release capacity than other composites, and there was an obvious synergistic effect between APP and CNCA-DA for PLA. IFR containing APP/CNCA-DA had good thermal stability and char-forming ability with the char residue 29.3% at 800°C under N 2 atmosphere. Scanning electron microscopy observation further indicated that IFR could promote forming continuous and compact intumescent char layer. The laser Raman spectroscopy analysis and X-ray photoelectron spectroscopy analysis results indicated that an appropriate graphitization degree of the residue char was formed, and more O and N were remained to form more cross-linking structure.

ZnO nanoparticles as chain elasticity reducer and structural elasticity enhancer: Correlating the degradating role and localization of ZnO with the morphological and mechanical properties of PLA/PP/ZnO nanocomposite

“…Today, the development and production of biodegradable plastics is one of the appropriate ways to control or reduce the accumulation of nonbiodegradable plastics to preserve the limited resources of fossil fuels and also to reduce the ecosystem destruction . Because of its biocompatibility and inherent biodegradability, polylactic acid (PLA) is one of the most important prominent biodegradable biopolymers that has found extensive applications in the various medical, packaging, and textile industries . The main drawback of this polymer returns to its brittleness, which diminishes its widespread application .…”

Flame retarded poly(lactic acid): A review

“…retardant Using intumescent flame retardants (IFR) is another promising way to enhance the fire performance of PLA due to its advantages, such as less smoke production, low toxicity, low corrosion, and no molten PLA dripping when burning [38,39]. However, the high water uptake/solubility of the conventional charring agent pentaerythritol (PER) disqualified its use for durable and engineering applications [40].…”

The intumescent flame‐retardant biocomposites of poly(lactic acid) containing surface‐coated ammonium polyphosphate and distiller's dried grains with solubles (DDGS)

“…Intumescent flame retardants (IFRs) have been used in flame‐retardant PLA composites . An IFR system is usually composed of an acid source, a blowing agent, and a carbon source.…”

“…The flame‐retardant effects depend on this layer because it can prevent the underlying materials from contacting oxygen and heat flux. Therefore, the charring agent plays an important role for IFR . In recent years, the biobased green flame retardants such as β‐cyclodextrin, DNA or protein, chitosan, starch, and lignin have been applied in flame retardancy of cotton fabrics, PLA, LDPE as the char source in the formulations.…”

“…[4][5][6] Intumescent flame retardants (IFRs) have been used in flameretardant PLA composites. 7,8 An IFR system is usually composed of an acid source, a blowing agent, and a carbon source. Typically, traditional IFRs comprise ammonium polyphosphate (APP; an acid source), pentaerythritol (a carbon source), and melamine (a blowing agent).…”