Improvement of Metal Caions in Polyoxometalate on Flame Retardant Efficiency of Polypropylene

doi:10.15541/jim20190529

Abstract

Abstract:

Polyoxometalate is a new type of catalyst, which has good application in many fields. The properties of phosphomolybdate (PMo) can be regulated by changing the metal cations. In this work, phosphomolybdic acid (PMA) anions were reacted with three different metal ions (Ni, Na and Zn) to form PMos, which were used as catalysts to improve the flame retardant efficiency of polypropylene/intumescent flame retardant (PP/IFR). The results show that the PP composites can obtain the UL-94 V0 grade of flame retardant efficiency by adding 25wt% IFR. However, if PMo is introduced into PP/IFR system, only 14.5wt% IFR and 0.5wt% sodium phosphomolybdate (NaPMo) or sodium phosphomolybdate (ZnPMo) are needed for PP to achieve the UL-94 V0 grade. While under the same formulation, nickel phosphomolybdate (NiPMo) can only make PP composite obtain the UL-94 V1 grade. Different metal ions have different catalytic activities in PP/IFR, among which NaPMo and ZnPMo match with IFR better than NiPMo. PMos can promote the reactions among IFR, slow down the heat release rate during combustion, and form a char layer with better barrier effect, so as to improve the matching of PP and IFR, and improve the flame retardant efficiency in the UL-94 test.

Key words: phosphomolybdate, metal caion, synergism, charring, flame retardant efficiency

CLC Number:

TQ322

LI Yimin,WANG Chengle,LI Juan. Improvement of Metal Caions in Polyoxometalate on Flame Retardant Efficiency of Polypropylene[J]. Journal of Inorganic Materials, 2020, 35(9): 1029-1033.

Figures/Tables 8

Table 1 Flame retardant properties of PP composites

No.	PP /wt%	IFR /wt%	Synergists /wt%	UL-94 3.2 mm	LOI
S1	100.0	0	No	NC	17.2
S2	85.0	15.0	No	NC	23.1
S3	85.0	14.5	0.5(NiPMo)	V-1	26.1
S4	85.0	14.5	0.5(NaPMo)	V-0	26.8
S5	85.0	14.5	0.5(ZnPMo)	V-0	27.0
S6	75.0	25.0	No	V-0	28.3

Fig. 1 TGA curves (a) and FT-IR spectra (b) of different PMos

Fig. 2 Photographs of infrared thermal imaging for PP composites

Fig. 3 TGA curves of PP composites tested in (a) N2 and (b) air

Fig. 4 Change of (a) HRR and (b) THR with time for PP composite at a heat flux of 35 kW/m2

Table 2 Data from cone calorimeter test

No.	TTI/s	PHRR/(kW·m^-2)	t_PHRR/s	THR/(MJ·m^-2)
S1	50	706.3	175	107.3
S2	45	383.9	294	109.5
S3	40	344.0	353	106.9
S4	43	407.8	363	112.8
S5	43	390.2	356	110.0

Fig. 5 Photos of char layers for PP composites after cone calorimeter test (a-e): S1-S5

Fig. 6 SEM images of char layers for PP composites after cone calorimeter test (a-d): S2-S5

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