Ammonium polyphosphate (APP), montmorillonite and PIN-FR cellulose (cellulose surface treated with diammonium phosphate and boric acid) were tested in polylactic acid foam (PLA, a bio-based polymer). The low density PLA foam (90% void) was produced by supercritical CO2 assisted continuous extrusion foaming. With cellulose (2%) and APP (15%) the foam achieved UL94 V-0 and a LOI of 31.5 vol% with total additives <20%. Without PIN-FR additives, the foams showed extremely high horizontal flame spreading rates, around 313 mm/min (UL-94 NR). The authors note that the montmorillonite – APP synergy was less marked in foams than in bulk PLA (see Wang et al. in pinfa Newsletter n°63).
“Flame retardancy of microcellular poly(lactic acid) foams prepared by supercritical CO2-assisted extrusion”, D. Vadas et al., Polymer Degradation and Stability 153 (2018) 100e108 https://doi.org/10.1016/j.polymdegradstab.2018.04.021