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Waste-to-resource strategy to fabricate environmentally benign flame retardants from waste phosphorus tailings
Composites Communications 19 (2020) 173–176
Contents lists available at ScienceDirect
Composites Communications journal homepage: www.elsevier.com/locate/coco
Short Communication
Waste-to-resource strategy to fabricate environmentally benign flame retardants from waste phosphorus tailings Keqing Zhou *, Qianqian Zhou, Kaili Gong, Jianshan Zhang Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan, Hubei, 430074, China
A R T I C L E I N F O
A B S T R A C T
Keywords: Waste phosphorus tailings Magnesium hydroxide Flame retardant Environmentally benign Polymeric composites Thermal properties
Environmentally benign magnesium hydroxide (MH) flame retardants with different morphologies were pre pared from waste phosphorus tailings by a combination of acidolysis reaction and hydrothermal method. The morphology, structure and dispersibility of MH were characterized by X-ray power diffraction, scanning electron microscope, and transmission electron microscope. The influences of the synthesized MH on the flame retardancy and smoke suppression properties of thermoplastic polyurethane were studied by cone calorimeter test and the flame retardant mechanism was discussed.
1. Introduction Waste phosphorus tailings, a solid waste produced in the process of phosphorus mineral flotation process, are mostly stored in tailings ponds, which have already become a threat to environment and human life [1]. Therefore, it is of great importance to reutilization of waste phosphorus tailings. At present, waste phosphorus tailings are mainly reutilized in the fields of construction, agricultural, ceramsite, flame retardancy, etc [2–4]. However, the utilization ratio of waste phos phorus tailings is still very low and a new, promising utilization method of waste phosphorus tailings is urgent to explore. As well known, phosphorus tailings mainly consist of dolomite (CaMg(CO3)2), magnesium oxide (MgO), silicon dioxide (SiO2) and other metal oxides, the content of Mg, Si, and Ca elements is relative high. Therefore, the comprehensive utilization of Mg resources included in waste phosphorus tailings will have significant economic and socio environmental benefits and has gained increasing attention [5]. Magnesium hydroxide (MH) has gained much attention and widely applied in many fields owing to its environmentally benign, nontoxic, thermally stable, and noncorrosive [6]. In last decade, as an alternative halogen-free flame retardant, MH has attracted considerable interests due to its low cost, high endothermic decomposition temperature, and suppressing the production of toxic and corrosive smoke during com bustion [7]. At present, MH is usually synthesized by precipitation method and magnesium salt solution including magnesium nitrate and magnesium chloride solutions are adopted as magnesium resources
which will be run out in one day. This prompted us to find a novel magnesium resource for preparing MH flame retardants. Inspired by this, it is of great significance to synthesize MH flame retardants by utilizing waste phosphorus tailings as magnesium resource. To the best of our knowledge, there are rare reports concerning the fabrication of MH flame retardants by selecting phosphorus tailings as raw materials. In this paper, MH flame retardants with two different morphologies including nanoplate and flower-like were prepared from waste phosphorus tailings by a combination of acidolysis reaction and hydrothermal method. The morphology and structure of MH were characterized by X-ray power diffraction (XRD), scanning electron mi croscope (SEM), and transmission electron microscopy (TEM). Cone calorimeter test (CCT) is carried out to investigate the fire behaviors of thermoplastic polyurethane (TPU) composites and the char residues are analyzed by SEM. 2. Materials and methods H2SO4, H2O2, NH3⋅H2O, C12H25SO3Na, Ethanol, N, N-Dime thylformamide (DMF) were provided by Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). TPU pellets (1180A) were purchased from BASF SE Company (Germany). Preparation of MH: Firstly, 50.0 g waste phosphorus tailings were added into 250 mL distilled water under strong mechanical stirring. Diluted H2SO4 solution were slowly dripped into the above-mentioned solution and stirring for 3 h at 50 � C. Then, 5 mL H2O2 was
* Corresponding author. E-mail address: [email protected] (K. Zhou). https://doi.org/10.1016/j.coco.2020.03.015 Received 16 February 2020; Received in revised form 25 March 2020; Accepted 30 March 2020 Available online 1 April 2020 2452-2139/© 2020 Elsevier Ltd. All rights reserved.
K. Zhou et al.
Composites Communications 19 (2020) 173–176
Fig. 1. XRD patterns, SEM and TEM images of MH1 (a, b, c) and MH2 (d, e, f), and SEM images of fracture surface of TPU, TPU/MH1, TPU/MH2 (g, h and i).
incorporated into the supernatant after centrifugation. The PH value of the mixture was kept in 6-7 adjusted by NH3⋅H2O. The mixed solution was stirred continuously for 1 h and then isolated by centrifugation to obtain supernatant. 1.2 g C12H25SO3Na was added into the obtained supernatant and stirred for 10 min and then PH value was adjusted to 11. Finally, the mixture was transferred to the reactor and reacted at 160 � C for 4 h. The obtained products named as MH2 were washed with distilled water, ethyl alcohol and then vacuum dried at 60 � C for 12 h. MH1 were synthesized by similar procedures without the addition of C12H25SO3Na. The synthesized MH1 and MH2 flame retardants were incorporated into TPU matrices by solvent blending method [3] and the mass ratio of MH is 4 wt%. XRD was performed via Rigaku D/Max-Ra rotating-anode X-ray diffractometer (Cu Kα, λ ¼ 0.1542 nm, Japan). SEM (Hitachi SU-8010, Japan) and TEM (JEM-2100F, Japan) were carried out to observe the morphologies of MH, fractured surfaces of TPU composites and char residues of TPU composites after combustion. CCT (Fire Testing Tech nology, UK) according to ISO 5660 was adopted to study the flamma bility of all samples at a heat flux of 35 kW/m2.
are detected in these two samples. The morphologies of the as-synthesized MH1 and MH2 were characterized by SEM and TEM. It can be observed that MH1 samples are in perfect flower-like morphology composed of many nanoplates (Fig. 1b and c). As shown in Fig. 1e and f, MH2 shows nanosheet structure and there is accumulation phenomenon between sheet layers. The above results indicate MH flame retardants with two different morphologies have been prepared successfully from waste phosphorus tailings. The dispersibility of the synthesized MH flame retardants in TPU composites was evaluated by SEM, and the fractured surfaces images of TPU/MH composites were shown in Fig. 1g–i. For pristine TPU, the smooth and featureless micro-morphology is exhibited in Fig. 1g. By comparison, for the TPU composites filled with MH flame retardants (Fig. 1h and i), the sections are rough and MH flame retardants are completely embedded in the TPU matrix without obvious agglomera tion, indicating the well dispersion state of the synthesized MH flame retardants. Cone calorimeter test (CCT) was employed to investigate the fire behavior of TPU and TPU composites. The heat release rate (HRR) curves of all samples are exhibited in Fig. 2a. Neat TPU is easy to ignite, the HRR rise rapidly to its peak heat release rate (PHRR) with a value of 1096 kW/m2. After incorporating 4 wt% as-synthesized MH flame re tardants from waste phosphorus tailings, the PHRR values of TPU composites decrease apparently to 701 and 562 kW/m2, corresponding to a 36% and 48.7% reduction, compared with that of neat TPU. These results indicate that the addition of MH can reduce the heat release rate
3. Results and discussion XRD was employed to investigate the phase composition and struc ture of MH1and MH2. The sharp peaks in Fig. 1a and d indicate that the MH1 and MH2 are well-crystallized, all the diffraction peaks can be well indexed with standard card JCPDS7-239 [8]. No other impurity phases 174
K. Zhou et al.
Composites Communications 19 (2020) 173–176
Fig. 2. HRR (a), SPR (b), CO (c) and CO2 (d) curves of TPU and its composites obtained from CCT.
of TPU during combustion. As well known, the smoke, smoke particulates and some toxic com pounds produced in a real fire is the main culprit for the fatality [9,10]. In general, magnesium hydroxide flame retardants have good smoke suppression effect during the combustion of polymer materials. There fore, the release of smoke and toxicity gases is studied. The smoke production release (SPR) curves of TPU and its composites are presented in Fig. 2b. It is apparent that the as-synthesized MH flame retardants could slow down the smoke release, as indicated by a lower SPR. The peak SPR values for TPU/MH1 and TPU/MH2 are 0.11, and 0.07 m2 s 1, corresponding to the reduction of 26.7% and 53.3%, respectively, compared with 0.15 m2 s 1 of neat TPU. The reduction of CO and CO2 production during the combustion process of polymer materials is conducive to reduce the toxicity of smoke and thus reduce the fire risk
[11]. Here, the toxic CO and CO2 yield curves of TPU and its composites are exhibited in Fig. 2c and d. It is visible that the CO and CO2 pro duction rates of the TPU composites with MH flame retardants decrease apparently in comparison with that of neat TPU. The peak values of CO and CO2 production rates of TPU/MH1 decreased by 41.5% and 36%, respectively, compared with that of neat TPU. For the TPU/MH2 sam ples, the peak values of CO and CO2 production rate show reduction of 61% and 53%, respectively. The inhibition of CO, CO2 yield and smoke release results in the decrease in the toxicity of gaseous products, which is conducive to fire rescue. The CCT results indicate that the fire hazards of TPU composites is inhibited significantly by incorporation of the synthesized MH flame retardants from waste phosphorus tailings. In particular, MH flame retardants with sheet structure show better inhi bition effects than flower-like structure, which is mainly attributed to
Fig. 3. SEM images of char residues of TPU and its composites after combustion test. 175
K. Zhou et al.
Composites Communications 19 (2020) 173–176
the good physical barrier effect of sheet structure [12]. In order to explain the prominent flame retardant and smoke sup pression effect, the morphologies of the char residues of TPU composites after combustion test were observed by SEM. As shown in Fig. 3 several apparent holes are observed in the residue char of pure TPU. By contrast, TPU/MH1 and TPU/MH2 composites present continuous and compact char structure without holes left on the surface, which can prevent the infiltration of oxygen and the spread of flammable gas and thus protect the inner composition from thermal decomposition. In addition, MH can absorb substantial heat and generate water molecules during thermal degradation, not only diluting the concentration of flammable gas and oxygen, but also reducing the high temperature in gas phase [13].
hazards of polymer materials. Acknowledgement This work was supported by the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan), (CUG160607), Scientific Research Plan Guidance Project of Hubei Province (B2017594). References [1] M. Li, X. Cong, L. Zhu, Mar. Georesour. Geotechnol. 35 (2017) 586–591. [2] Y. Yang, Z. Wei, Y. Chen, Y. Li, X. Li, Construct. Build. Mater. 155 (2017) 1081–1090. [3] Q.Q. Zhou, C.K. Liu, K.Q. Zhou, X. Xuan, C.L. Shi, Polym. Adv. Technol. 31 (2019) 4–14. [4] K.Q. Zhou, K.L. Gong, Q.Q. Zhou, S.J. Zhao, H.L. Guo, X.D. Qian, J. Clean. Prod. 257 (2020), 120606. [5] J. Du, Z. Chen, Y.L. Wu, M.D. Yang, J. Dang, J.J. Yuan, Turk. J. Chem. 37 (2013) 228–238. [6] S. Guo, L. Yang, B. Dai, Mater. Lett. 236 (2019) 448–451. [7] S.P. Liu, J.R. Ying, X.P. Zhou, X.L. Xie, Mater. Lett. 63 (2009) 911–913. [8] G. Davood, S. Masoud, S. Mohammad, Composites Part B 45 (2013) 550–555. [9] D.T. Hu, Q.Q. Zhou, K.Q. Zhou, J. Appl. Polym. Sci. 136 (2019) 48220. [10] S.G. Wang, R. Gao, K.Q. Zhou, J. Colloid Interface Sci. 536 (2019) 127–134. [11] K.Q. Zhou, R. Gao, X.D. Qian, J. Hazard Mater. 338 (2017) 343–355. [12] G.B. Huang, J.R. Gao, X. Wang, H.D. Liang, C.H. Ge, Mater. Lett. 66 (2012) 187–189. [13] S.J. Zhao, J.Y. Yin, K.Q. Zhou, Y. Cheng, B. Yu, Composites Part A 122 (2019) 77–84.
4. Conclusion In this work, magnesium hydroxide flame retardants with different morphologies were successfully prepared from waste phosphorus tail ings. The structure, morphology and dispersibility of the as-synthesized MH were carried out via XRD, SEM and TEM measurements, then the MH flame retardants were incorporated into TPU matrices by solvent blending method. CCT results indicated the PHHR, P-SPR values, CO and CO2 production rate of the TPU composites filled with MH all decreased obviously, in comparison with those of neat TPU. The enhanced flame retardancy was presumably ascribed to the physical barrier effect, cat alytic charring effect, diluting and cooling effect of MH. The imple mentation of this research will have great significance for realizing the resource utilization of waste phosphorus tailings and reducing fire
176
Contents lists available at ScienceDirect
Composites Communications journal homepage: www.elsevier.com/locate/coco
Short Communication
Waste-to-resource strategy to fabricate environmentally benign flame retardants from waste phosphorus tailings Keqing Zhou *, Qianqian Zhou, Kaili Gong, Jianshan Zhang Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan, Hubei, 430074, China
A R T I C L E I N F O
A B S T R A C T
Keywords: Waste phosphorus tailings Magnesium hydroxide Flame retardant Environmentally benign Polymeric composites Thermal properties
Environmentally benign magnesium hydroxide (MH) flame retardants with different morphologies were pre pared from waste phosphorus tailings by a combination of acidolysis reaction and hydrothermal method. The morphology, structure and dispersibility of MH were characterized by X-ray power diffraction, scanning electron microscope, and transmission electron microscope. The influences of the synthesized MH on the flame retardancy and smoke suppression properties of thermoplastic polyurethane were studied by cone calorimeter test and the flame retardant mechanism was discussed.
1. Introduction Waste phosphorus tailings, a solid waste produced in the process of phosphorus mineral flotation process, are mostly stored in tailings ponds, which have already become a threat to environment and human life [1]. Therefore, it is of great importance to reutilization of waste phosphorus tailings. At present, waste phosphorus tailings are mainly reutilized in the fields of construction, agricultural, ceramsite, flame retardancy, etc [2–4]. However, the utilization ratio of waste phos phorus tailings is still very low and a new, promising utilization method of waste phosphorus tailings is urgent to explore. As well known, phosphorus tailings mainly consist of dolomite (CaMg(CO3)2), magnesium oxide (MgO), silicon dioxide (SiO2) and other metal oxides, the content of Mg, Si, and Ca elements is relative high. Therefore, the comprehensive utilization of Mg resources included in waste phosphorus tailings will have significant economic and socio environmental benefits and has gained increasing attention [5]. Magnesium hydroxide (MH) has gained much attention and widely applied in many fields owing to its environmentally benign, nontoxic, thermally stable, and noncorrosive [6]. In last decade, as an alternative halogen-free flame retardant, MH has attracted considerable interests due to its low cost, high endothermic decomposition temperature, and suppressing the production of toxic and corrosive smoke during com bustion [7]. At present, MH is usually synthesized by precipitation method and magnesium salt solution including magnesium nitrate and magnesium chloride solutions are adopted as magnesium resources
which will be run out in one day. This prompted us to find a novel magnesium resource for preparing MH flame retardants. Inspired by this, it is of great significance to synthesize MH flame retardants by utilizing waste phosphorus tailings as magnesium resource. To the best of our knowledge, there are rare reports concerning the fabrication of MH flame retardants by selecting phosphorus tailings as raw materials. In this paper, MH flame retardants with two different morphologies including nanoplate and flower-like were prepared from waste phosphorus tailings by a combination of acidolysis reaction and hydrothermal method. The morphology and structure of MH were characterized by X-ray power diffraction (XRD), scanning electron mi croscope (SEM), and transmission electron microscopy (TEM). Cone calorimeter test (CCT) is carried out to investigate the fire behaviors of thermoplastic polyurethane (TPU) composites and the char residues are analyzed by SEM. 2. Materials and methods H2SO4, H2O2, NH3⋅H2O, C12H25SO3Na, Ethanol, N, N-Dime thylformamide (DMF) were provided by Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). TPU pellets (1180A) were purchased from BASF SE Company (Germany). Preparation of MH: Firstly, 50.0 g waste phosphorus tailings were added into 250 mL distilled water under strong mechanical stirring. Diluted H2SO4 solution were slowly dripped into the above-mentioned solution and stirring for 3 h at 50 � C. Then, 5 mL H2O2 was
* Corresponding author. E-mail address: [email protected] (K. Zhou). https://doi.org/10.1016/j.coco.2020.03.015 Received 16 February 2020; Received in revised form 25 March 2020; Accepted 30 March 2020 Available online 1 April 2020 2452-2139/© 2020 Elsevier Ltd. All rights reserved.
K. Zhou et al.
Composites Communications 19 (2020) 173–176
Fig. 1. XRD patterns, SEM and TEM images of MH1 (a, b, c) and MH2 (d, e, f), and SEM images of fracture surface of TPU, TPU/MH1, TPU/MH2 (g, h and i).
incorporated into the supernatant after centrifugation. The PH value of the mixture was kept in 6-7 adjusted by NH3⋅H2O. The mixed solution was stirred continuously for 1 h and then isolated by centrifugation to obtain supernatant. 1.2 g C12H25SO3Na was added into the obtained supernatant and stirred for 10 min and then PH value was adjusted to 11. Finally, the mixture was transferred to the reactor and reacted at 160 � C for 4 h. The obtained products named as MH2 were washed with distilled water, ethyl alcohol and then vacuum dried at 60 � C for 12 h. MH1 were synthesized by similar procedures without the addition of C12H25SO3Na. The synthesized MH1 and MH2 flame retardants were incorporated into TPU matrices by solvent blending method [3] and the mass ratio of MH is 4 wt%. XRD was performed via Rigaku D/Max-Ra rotating-anode X-ray diffractometer (Cu Kα, λ ¼ 0.1542 nm, Japan). SEM (Hitachi SU-8010, Japan) and TEM (JEM-2100F, Japan) were carried out to observe the morphologies of MH, fractured surfaces of TPU composites and char residues of TPU composites after combustion. CCT (Fire Testing Tech nology, UK) according to ISO 5660 was adopted to study the flamma bility of all samples at a heat flux of 35 kW/m2.
are detected in these two samples. The morphologies of the as-synthesized MH1 and MH2 were characterized by SEM and TEM. It can be observed that MH1 samples are in perfect flower-like morphology composed of many nanoplates (Fig. 1b and c). As shown in Fig. 1e and f, MH2 shows nanosheet structure and there is accumulation phenomenon between sheet layers. The above results indicate MH flame retardants with two different morphologies have been prepared successfully from waste phosphorus tailings. The dispersibility of the synthesized MH flame retardants in TPU composites was evaluated by SEM, and the fractured surfaces images of TPU/MH composites were shown in Fig. 1g–i. For pristine TPU, the smooth and featureless micro-morphology is exhibited in Fig. 1g. By comparison, for the TPU composites filled with MH flame retardants (Fig. 1h and i), the sections are rough and MH flame retardants are completely embedded in the TPU matrix without obvious agglomera tion, indicating the well dispersion state of the synthesized MH flame retardants. Cone calorimeter test (CCT) was employed to investigate the fire behavior of TPU and TPU composites. The heat release rate (HRR) curves of all samples are exhibited in Fig. 2a. Neat TPU is easy to ignite, the HRR rise rapidly to its peak heat release rate (PHRR) with a value of 1096 kW/m2. After incorporating 4 wt% as-synthesized MH flame re tardants from waste phosphorus tailings, the PHRR values of TPU composites decrease apparently to 701 and 562 kW/m2, corresponding to a 36% and 48.7% reduction, compared with that of neat TPU. These results indicate that the addition of MH can reduce the heat release rate
3. Results and discussion XRD was employed to investigate the phase composition and struc ture of MH1and MH2. The sharp peaks in Fig. 1a and d indicate that the MH1 and MH2 are well-crystallized, all the diffraction peaks can be well indexed with standard card JCPDS7-239 [8]. No other impurity phases 174
K. Zhou et al.
Composites Communications 19 (2020) 173–176
Fig. 2. HRR (a), SPR (b), CO (c) and CO2 (d) curves of TPU and its composites obtained from CCT.
of TPU during combustion. As well known, the smoke, smoke particulates and some toxic com pounds produced in a real fire is the main culprit for the fatality [9,10]. In general, magnesium hydroxide flame retardants have good smoke suppression effect during the combustion of polymer materials. There fore, the release of smoke and toxicity gases is studied. The smoke production release (SPR) curves of TPU and its composites are presented in Fig. 2b. It is apparent that the as-synthesized MH flame retardants could slow down the smoke release, as indicated by a lower SPR. The peak SPR values for TPU/MH1 and TPU/MH2 are 0.11, and 0.07 m2 s 1, corresponding to the reduction of 26.7% and 53.3%, respectively, compared with 0.15 m2 s 1 of neat TPU. The reduction of CO and CO2 production during the combustion process of polymer materials is conducive to reduce the toxicity of smoke and thus reduce the fire risk
[11]. Here, the toxic CO and CO2 yield curves of TPU and its composites are exhibited in Fig. 2c and d. It is visible that the CO and CO2 pro duction rates of the TPU composites with MH flame retardants decrease apparently in comparison with that of neat TPU. The peak values of CO and CO2 production rates of TPU/MH1 decreased by 41.5% and 36%, respectively, compared with that of neat TPU. For the TPU/MH2 sam ples, the peak values of CO and CO2 production rate show reduction of 61% and 53%, respectively. The inhibition of CO, CO2 yield and smoke release results in the decrease in the toxicity of gaseous products, which is conducive to fire rescue. The CCT results indicate that the fire hazards of TPU composites is inhibited significantly by incorporation of the synthesized MH flame retardants from waste phosphorus tailings. In particular, MH flame retardants with sheet structure show better inhi bition effects than flower-like structure, which is mainly attributed to
Fig. 3. SEM images of char residues of TPU and its composites after combustion test. 175
K. Zhou et al.
Composites Communications 19 (2020) 173–176
the good physical barrier effect of sheet structure [12]. In order to explain the prominent flame retardant and smoke sup pression effect, the morphologies of the char residues of TPU composites after combustion test were observed by SEM. As shown in Fig. 3 several apparent holes are observed in the residue char of pure TPU. By contrast, TPU/MH1 and TPU/MH2 composites present continuous and compact char structure without holes left on the surface, which can prevent the infiltration of oxygen and the spread of flammable gas and thus protect the inner composition from thermal decomposition. In addition, MH can absorb substantial heat and generate water molecules during thermal degradation, not only diluting the concentration of flammable gas and oxygen, but also reducing the high temperature in gas phase [13].
hazards of polymer materials. Acknowledgement This work was supported by the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan), (CUG160607), Scientific Research Plan Guidance Project of Hubei Province (B2017594). References [1] M. Li, X. Cong, L. Zhu, Mar. Georesour. Geotechnol. 35 (2017) 586–591. [2] Y. Yang, Z. Wei, Y. Chen, Y. Li, X. Li, Construct. Build. Mater. 155 (2017) 1081–1090. [3] Q.Q. Zhou, C.K. Liu, K.Q. Zhou, X. Xuan, C.L. Shi, Polym. Adv. Technol. 31 (2019) 4–14. [4] K.Q. Zhou, K.L. Gong, Q.Q. Zhou, S.J. Zhao, H.L. Guo, X.D. Qian, J. Clean. Prod. 257 (2020), 120606. [5] J. Du, Z. Chen, Y.L. Wu, M.D. Yang, J. Dang, J.J. Yuan, Turk. J. Chem. 37 (2013) 228–238. [6] S. Guo, L. Yang, B. Dai, Mater. Lett. 236 (2019) 448–451. [7] S.P. Liu, J.R. Ying, X.P. Zhou, X.L. Xie, Mater. Lett. 63 (2009) 911–913. [8] G. Davood, S. Masoud, S. Mohammad, Composites Part B 45 (2013) 550–555. [9] D.T. Hu, Q.Q. Zhou, K.Q. Zhou, J. Appl. Polym. Sci. 136 (2019) 48220. [10] S.G. Wang, R. Gao, K.Q. Zhou, J. Colloid Interface Sci. 536 (2019) 127–134. [11] K.Q. Zhou, R. Gao, X.D. Qian, J. Hazard Mater. 338 (2017) 343–355. [12] G.B. Huang, J.R. Gao, X. Wang, H.D. Liang, C.H. Ge, Mater. Lett. 66 (2012) 187–189. [13] S.J. Zhao, J.Y. Yin, K.Q. Zhou, Y. Cheng, B. Yu, Composites Part A 122 (2019) 77–84.
4. Conclusion In this work, magnesium hydroxide flame retardants with different morphologies were successfully prepared from waste phosphorus tail ings. The structure, morphology and dispersibility of the as-synthesized MH were carried out via XRD, SEM and TEM measurements, then the MH flame retardants were incorporated into TPU matrices by solvent blending method. CCT results indicated the PHHR, P-SPR values, CO and CO2 production rate of the TPU composites filled with MH all decreased obviously, in comparison with those of neat TPU. The enhanced flame retardancy was presumably ascribed to the physical barrier effect, cat alytic charring effect, diluting and cooling effect of MH. The imple mentation of this research will have great significance for realizing the resource utilization of waste phosphorus tailings and reducing fire
176