Synthesis and characterization of a novel flame retardant, poly(lactic acid-co-3,3′-diaminobenzidine)

Figures & data

Scheme 1 The synthetic route of P(LA-co-DAB).

Table 1. The influences of different catalysts on the reaction.^a

Run	Catalysts	Appearance of product	[η] (dL g^−1)	Yield (%)
1	ZnO	Yellowish powder	0.28	42
2	SnCl2	Yellow powder	0.34	43
3	SnO	White powder	0.41	20
4	TSA	Yellow powder	0.20	29
5	ZnCl2	White powder	0.38	33
^aAll runs are polymerized with a molar feed ratio LA/DAB of 80/1, a prepolymerization temperature of 140 °C, a prepolymerization time of 8 h, a polycondensation temperature of 160 °C, a polycondensation time of 6 h, and a catalyst quantity of 0.3 wt.%.

Table 2. The influences of catalysts dosage on the reaction.^a

Run	Catalyst dosage (wt.%)	Appearance of product	[η] (dL g^−1)	Yield (%)
1	0.1	Yellowish powder	0.28	30
2	0.3	White powder	0.41	20
3	0.5	White powder	0.58	23
4	0.7	White powder	0.71	30
5	0.9	Yellow powder	0.45	28
^aAll runs are polymerized with a molar feed ratio LA/DAB of 80/1, a prepolymerization temperature of 140 °C, a prepolymerization time of 8 h, a polycondensation temperature of 160 °C, a polycondensation time of 6 h, and using SnO as the catalyst.

Table 3. The influences of melt polymerization temperature on the reaction.^a

Run	Temperature (°C)	Appearance of product	[η] (dL g^−1)	Yield (%)
1	130	White powder	0.50	34
2	140	White powder	0.58	35
3	150	White powder	0.64	34
4	160	White powder	0.71	30
5	170	Yellowish powder	0.61	38
^aAll runs are polymerized with a molar feed ratio LA/DAB of 80/1, a prepolymerization temperature of 140 °C, a prepolymerization time of 8 h, a polycondensation time of 6 h, and using 0.7 wt.% SnO as the catalyst.

Table 4. The influences of melt polymerization time on the reaction.^a

Run	Time (h)	Appearance of product	[η] (dL g^−1)	Yield (%)
1	4	White powder	0.55	40
2	6	White powder	0.71	30
3	8	Yellowish powder	0.67	37
4	10	Yellowish powder	0.64	34
5	12	Yellow powder	0.47	31
^aAll runs are polymerized with a molar feed ratio LA/DAB of 80/1, a prepolymerization temperature of 140 °C, a prepolymerization time of 8 h, a polycondensation temperature of 160 °C, and using 0.7 wt.% SnO as the catalyst.

Table 5. The influences of different molar feed ratios on yield, [η] and M _n of the copolymers.^a

Run	LA/DAB		Appearance of product	Yield (%)	[η] (dL g^−1)	M NMR ^b (Da)	M n (Da)	M w (Da)	M w/M n ^c
	Feed	Test^b
1	20/1	12/1	Gray powder	33	0.50	1300	1600	2300	1.44
2	40/1	17/1	White powder	38	0.64	1700	2200	3800	1.73
3	80/1	29/1	White powder	30	0.71	2600	2500	4800	1.92
4	120/1	36/1	White powder	31	0.95	2800	3000	5900	1.97
5	160/1	57/1	White powder	21	1.10	4300	2800	5400	1.93
^aAll runs are polymerized with a prepolymerization temperature of 140 °C, a prepolymerization time of 8 h, a polycondensation temperature of 160 °C, a polycondensation time of 6 h, and using 0.7 wt.% SnO as the catalyst.^bTested by ^1H-NMR, and for M NMR using 100 Da as unit.^cThe peak shape in all GPC curves is only a single peak.

Figure 1 FTIR spectrum of P(LA-co-DAB) synthesized as the molar feed ratio 80/1 (LA/DAB).

Figure 2 FTIR spectra of P(LA-co-DAB)s with different molar feed ratios (LA/DAB).

Figure 3 ¹H NMR spectrum of P(LA-co-DAB) synthesized as the molar feed ratio 80/1 (LA/DAB).

Figure 4 XRD spectra of P(LA-co-DAB)s with different feed molar ratios (LA/DAB).

Table 6. The influences of different molar feed ratios on XRD results of P(LA-co-DAB)s.^a

Run	LA/DAB	2θ		X c (%)	Crystallite dimension (10^−10m)
		Face (110)	Face (020)		L 110	L 020
1	20/1	Amorphous
2	40/1	Amorphous
3	80/1	16.7	19.1	9.9	246.7	146.9
4	120/1	16.7	19.0	16.2	262.3	142.4
5	160/1	16.7	19.1	17.4	254.7	142.4
PDLLA [19]		16.7	19.1	20.8	154.4	83.9
^aAll runs are polymerized with a prepolymerization temperature of 140 °C, a prepolymerization time of 8 h, a polycondensation temperature of 160 °C, a polycondensation time of 6 h, and using 0.7 wt.% SnO as the catalyst.

Table 7. The influences of different molar feed ratios on DSC and TGA results of P(LA-co-DAB)s.^a

Run	LA/DAB	T g (°C)	T 5% (°C)	T 10% (°C)	T p1 (°C)	T f1 (°C)	T p2 (°C)	T f2 (°C)
1	20/1	54.1	227.8	253.0	293.3	386.0	644.7	673.0
2	40/1	53.2	255.2	273.5	307.4	387.0	596.6	617.6
3	80/1	51.8	257.9	264.4	305.8	384.0	545.1	566.4
4	120/1	47.9	259.1	275.4	318.5	381.0	538.3	570.1
5	160/1	45.4	263.1	276.6	323.9	379.0	511.5	538.5
PDLLA^b		54.6 [19]	238.4	250.9	284.3	295.4	–	–
IFR-PLA1 [11]		53.7	235	–	271	–	–	–
IFR-PLA4 [11]		56.3	250	–	279	–	–	–
^aAll runs are polymerized with a prepolymerization temperature of 140 °C, a prepolymerization time of 8 h, a polycondensation temperature of 160 °C, a polycondensation time of 6 h, and using 0.7 wt.% SnO as the catalyst.^bPDLLA used as comparative sample is polymerized under the same conditions except for special explanation.

Figure 5 TG curves of P(LA-co-DAB)s with different feed molar ratios (LA/DAB).

Figure 6 curves of P(LA-co-DAB)s with different feed molar ratios (LA/DAB).

Table 8. The char yield of P(LA-co-DAB)s at different thermal decomposition temperatures.^a

Run	LA/DAB	Char yield (%)
		375 °C	400 °C	450 °C	500 °C	600 °C
1	20/1	37.51	36.60	34.59	21.65	19.33
2	40/1	29.01	27.82	25.75	22.54	7.90
3	80/1	17.61	16.27	13.91	9.97	0.48
4	120/1	11.14	10.04	8.24	5.59	0
5	160/1	8.95	8.06	6.32	3.80	1.64
PDLLA^b		0	0	0	0	0
IFR-PLA1 [11]		6.8	4.8	2.2	–	–
IFR-PLA4 [11]		15.6	11.0	3.1	–	–
^aAll runs are polymerized with a prepolymerization temperature of 140 °C, a prepolymerization time of 8 h, a polycondensation temperature of 160 °C, a polycondensation time of 6 h, and using 0.7 wt.% SnO as the catalyst.^bPDLLA used as comparative sample is polymerized under the same conditions.

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