| The flame retardant effect of 1-ethyl-3- methylimidazolium six fluoride phosphate ionic liquid([EMIM]PF6) was studied in thermoplastic polyurethane elastomer(TPU) composites. The synergistic flame retardant and smoke suppression effects between [EMIM]PF6 and several phosphate flame retardants were investigated in TPU composites. A series of flame retardant TPU composites were prepared by melt blending method using ammonium polyphosphate(APP), aluminum hypophosphite(AHP), diethyl phosphinic acid aluminum(ADP) as flame retardants, and [EMIM]PF6 as synergism. And, the flame retardant and smoke suppression properties of TPU composites were evaluated by limiting oxygen index(LOI), vertical burning test(UL 94), cone calorimeter test(CCT), smoke density test(SDT), and thermogravimetric analysis/infrared spectrometry(TG-IR). The related results are shown in the following.0 Flame retardant effect of [EMIM]PF6 in TPU. The CCT results showed that pHRR of the sample with 2.0 wt% [EMIM]PF6 is 73% lower than that of TPU-0; THR is 11% lower than that of TPU-0, and decreased with the increase of [EMIM]PF6, indicating that [EMIM]PF6 can effectively reduce the heat release of TPU/[EMIM]PF6. SPR is 58% lower than that of TPU-0, and SF is 64% lower than that of TPU-0, indicating that [EMIM]PF6 can effectively reduce the smoke release of TPU/[EMIM]PF6. The residual mass of carbon resid ue increased by 7.4% compared with TPU-0, which indicated that [EMIM]PF6 could effectively increase the char residue weight of TPU/[EMIM]PF6. SDT results show that luminous flux value of the sample(2.0 wt% [EMIM]PF6) is 13% higher than that of TPU-0 at the test condition without flame, indicating that [EMIM]PF6 can effectively reduce the smoke release of TPU/[EMIM]PF6. LOI results showed that the LOI of the sample with 0.5 wt% [EMIM]PF6 is increased from 24.75 to 27.75. TG results showed that the residual carbon mass of the sample with 2.0 wt% [EMIM]PF6 is 23% higher than that of TPU-0. The above results show that [EMIM]PF6 can effectively reduce the heat release and smoke release, and improve the thermal stability of TPU materials when the adding amount is 2%.⑵ The synergistic flame retardant effect between [EMIM]PF6 and APP was studied in TPU composites. The CCT results showed that the pHRR of the sample with 0.25 wt% [EMIM]PF6 is 42% lower than that of APP-1; THR is 34% lower than that of APP-1, which indicates that [EMIM]PF6 can effectively reduce the heat release of TPU/APP/[EMIM]PF6 composites. SF is 28% lower than that of APP-1, which indicates that [EMIM]PF6 and APP can reduce the smoke release of TPU/APP/[EMIM]PF6 composites. SDT results showed that luminous flux value of the sample with 0.50 wt% [EMIM]PF6 is 79% higher than that of APP-1, and specific optical density is 45% higher than that of APP-1 with flame. The luminous flux value of sample with 0.25 wt% [EMIM]PF6 is 8.4% higher than that of APP-1, and specific optical density is 6.4% higher than that of APP-1 without flame, indicating that [EMIM]PF6 and APP can reduce the smoke density of TPU/APP/[EMIM]PF6 composites. LOI results showed that the sample(0.50 wt% [EMIM]PF6) has the highest LOI value(32.75). UL 94 results show that the grade is V-0. The combustion time is shorter, sample melting and dripping phenomenon has improved.⑶ The synergistic flame retardant effect between [EMIM]PF6 and AHP was studied in TPU composites. CCT results showed that THR of the sample with 0.0625 wt% [EMIM]PF6 is 23% lower than that of AHP-1, the pHRR is 7% lower than that of AHP-1, which indicates that [EMIM]PF6 and AHP can reduce the heat release of TPU/AHP/[EMIM]PF6 composites. SF is 7% lower than that of AHP-1 and TSR is 23% lower than that of AHP-1, which indicates that [EMIM]PF6 and AHP can reduce the smoke release of TPU/AHP/[EMIM]PF6 composites. The remaining char residue weight is 26% more than that of AHP-1, which indicates the synergistic effect between [EMIM]PF6 and AHP enhance the char forming property of TPU/AHP/ [EMIM]PF6 composites. SDT results showed that luminous flux value of the sample with 0.03125 wt% [EMIM]PF6 is 10% higher than that of AHP-1 and specific optical density is 49% lower than that of AHP-1 with flame. The luminous flux of the sample(0.125 wt% [EMIM]PF6) is 2% higher than that of AHP-1 and specific optical density is 21% lower than that of AHP-1 without flame. These results indicate that [EMIM]PF6 and AHP can reduce the smoke density of TPU/AHP/[EMIM]PF6 composites. LOI results showed that the sample(0.03125 wt% [EMIM]PF6) has the highest LOI value increased from 24.75 to 36.25. The vertical burning test results showed that the synergistic effect between [EMIM]PF6 and AHP effectively improves the UL 94 grade of materials to V-0 level. The flame retardant and smoke suppression properties of TPU/AHP/[EMIM]PF6 composites are improved based on the synergistic effect between [EMIM]PF6 and AHP.⑷ The synergistic flame retardant effect between [EMIM]PF6 and ADP was studied in TPU composites. CCT results show that THR of sample(0.3 wt% [EMIM]PF6) is 24% lower than that of ADP-1 and pHRR is 39% lower than that of ADP-1, which indicates that [EMIM]PF6 and ADP can reduce the heat release of TPU/ADP/[EMIM]PF6 composites. SF is 56% lower than that of ADP-1 and SPR is 54% lower than that of ADP-1, which indicates that [EMIM]PF6 and ADP can reduce the smoke release of TPU/ADP/[EMIM]PF6 composites. The quality of carbon residual is 9% higher than that of ADP-1, which enhances the thermal stability of TPU/ADP/[EMIM]PF6 composites by the synergistic effect between [EMIM]PF6 and ADP. LOI results showed that the sample with 0.3 wt% [EMIM]PF6 has the highest LOI value of 36.25, and the serious phenomenon of the droplet is improved.In summary, [EMIM]PF6 has good flame retardance and smoke suppression effect as a single flame retardant of TPU materials. As a synergistic flame retardant with APP, AHP, ADP, [EMIM]PF6 also has good flame retardance and smoke suppression effect in TPU composites. |
