Table 4. UL-94 and LOI test data of PP and its flame-retardant composites^a.

Sample	UL-94					LOI [%]
	t 1 [s]	t 2 [s]	Dripping	Cotton ignited	Rating
PP	—	—	Yes	Yes	NR	17.5
P1	7.6 ± 0.5	31.3 ± 1.3	Yes	Yes	V-2	23.5
P2	1.0 ± 0.1	1.3 ± 0.1	No	No	V-0	35.7
P3	4.1 ± 0.3	2.8 ± 0.3	Yes	Yes	V-2	22.6
P4	3.1 ± 0.3	2.2 ± 0.3	Yes	Yes	V-2	24.6
P5	2.8 ± 0.2	1.9 ± 0.2	Yes	Yes	V-2	25.3
P6	0.9 ± 0.1	1.2 ± 0.1	No	No	V-0	32.8
P7	0.9 ± 0.1	1.3 ± 0.3	No	No	V-0	33.1

^a t ₁ and t₂ in UL-94 refer to the time from the start of combustion to the complete extinction of the sample after the first and second ignitions in the test, respectively.