The results of the vertical burning tests of RPUFs.

Samples	Density (kg m−3)	Burning time (s)	Number of combustion droplets	Residual mass fraction (wt%)	Flame height (mm)
RPUF0	59.86	56.6	6	33.35	>250
RPUF-D5	74.45	49.6	0	56.25	<250
RPUF-D10	67.61	16.1	0	85.21	<250
RPUF-D15	62.92	4.4	0	85.61	<250
RPUF-A5	63.69	16.8	0	90.23	<250
RPUF-A10	56.02	17.1	0	85.23	<250
RPUF-A15	62.08	12.5	0	90.89	<250