Inorganic Flame-Retardant Coatings Based on Magnesium Potassium Phosphate Hydrate
A magnesium potassium phosphate hydrate-based flame-retardant coating (MKPC) is formulated by dead-burnt magnesium oxide (magnesia) and potassium dihydrogen phosphate (KH<sub>2</sub>PO<sub>4</sub>), behaving as a matrix. Constituents of the MKPC include wollastonite, vermicul...
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2022-08-01
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| Online Access: | https://www.mdpi.com/1996-1944/15/15/5317 |
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| author | Sin-Nan Chen Ching Lin Hao-Lun Hsu Xin-Han Chen Yu-Chang Huang Tar-Hwa Hsieh Ko-Shan Ho Yu-Jun Lin |
| author_facet | Sin-Nan Chen Ching Lin Hao-Lun Hsu Xin-Han Chen Yu-Chang Huang Tar-Hwa Hsieh Ko-Shan Ho Yu-Jun Lin |
| author_sort | Sin-Nan Chen |
| collection | DOAJ |
| description | A magnesium potassium phosphate hydrate-based flame-retardant coating (MKPC) is formulated by dead-burnt magnesium oxide (magnesia) and potassium dihydrogen phosphate (KH<sub>2</sub>PO<sub>4</sub>), behaving as a matrix. Constituents of the MKPC include wollastonite, vermiculite, aluminum fluoride, aluminum trihydroxide, and calcium carbonate. Some of the ingredients inter-react to produce mullite whiskers at high temperatures, despite an acid-base hydration induced reaction between magnesia and KH<sub>2</sub>PO<sub>4</sub>. The MKPC’s thermal, corrosion-resistant, mechanical, and flame-resistant properties were analyzed using scanning electron microscopy, electrochemical corrosion testing, compression testing, thermogravimetric analysis, and freeze/thaw tests. The results show that with the molar ratio = 4 of magnesia to KH<sub>2</sub>PO<sub>4</sub>, MKPC demonstrates lower thermal conductivity (0.19 W/m K), along with better corrosion resistance, stronger compressive strength (10.5 MPa), and higher bonding strength (6.62 kgf/cm<sup>2</sup>) to the steel substrate. Furthermore, acceptable additives to the formulation could enhance its flame-retardancy and increase its mechanical strength as well. Mullite whisker formed from the interaction of wollastonite, aluminum trihydroxide, and aluminum fluoride acts as an outer ceramic shield that enhances mechanical strength and compactness. In addition, Mg-containing minerals with calcium carbonate treated at high temperatures, transform into magnesium calcium carbonate after releasing CO<sub>2</sub>. At the optimum composition of MKPC (magnesia/KH<sub>2</sub>PO<sub>4</sub> molar ratio = 4; wollastonite:vermiculite = 20:10 wt.%; aluminum trihydroxide = 10 wt.%; and calcium carbonate = 5 wt.%), coated on a steel substrate, the flame-resistance limit results exhibit below 200 °C on the back surface of the steel substrate after one hour of flaming (ca. 1000 °C) on the other surface, and the flame-resistance rating results demonstrate only 420 °C on the back surface of the steel substrate after three hours of flaming (>1000 °C) on the other surface. Both requirements for the flame-resistance limit and three-hour flame-resistance rating are met with the optimum compositions, indicating that MKPC plays an effective role in establishing flame-retardancy. |
| first_indexed | 2024-03-09T10:07:03Z |
| format | Article |
| id | doaj.art-067a533439a94b099d3566c20294ee4a |
| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-09T10:07:03Z |
| publishDate | 2022-08-01 |
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| series | Materials |
| spelling | doaj.art-067a533439a94b099d3566c20294ee4a2023-12-01T23:01:11ZengMDPI AGMaterials1996-19442022-08-011515531710.3390/ma15155317Inorganic Flame-Retardant Coatings Based on Magnesium Potassium Phosphate HydrateSin-Nan Chen0Ching Lin1Hao-Lun Hsu2Xin-Han Chen3Yu-Chang Huang4Tar-Hwa Hsieh5Ko-Shan Ho6Yu-Jun Lin7Department of Chemical and Materials Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807618, TaiwanDepartment of Chemical and Materials Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807618, TaiwanDepartment of Chemical and Materials Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807618, TaiwanDepartment of Chemical and Materials Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807618, TaiwanDepartment of Chemical and Materials Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807618, TaiwanDepartment of Chemical and Materials Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807618, TaiwanDepartment of Chemical and Materials Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807618, TaiwanDepartment of Chemical and Materials Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807618, TaiwanA magnesium potassium phosphate hydrate-based flame-retardant coating (MKPC) is formulated by dead-burnt magnesium oxide (magnesia) and potassium dihydrogen phosphate (KH<sub>2</sub>PO<sub>4</sub>), behaving as a matrix. Constituents of the MKPC include wollastonite, vermiculite, aluminum fluoride, aluminum trihydroxide, and calcium carbonate. Some of the ingredients inter-react to produce mullite whiskers at high temperatures, despite an acid-base hydration induced reaction between magnesia and KH<sub>2</sub>PO<sub>4</sub>. The MKPC’s thermal, corrosion-resistant, mechanical, and flame-resistant properties were analyzed using scanning electron microscopy, electrochemical corrosion testing, compression testing, thermogravimetric analysis, and freeze/thaw tests. The results show that with the molar ratio = 4 of magnesia to KH<sub>2</sub>PO<sub>4</sub>, MKPC demonstrates lower thermal conductivity (0.19 W/m K), along with better corrosion resistance, stronger compressive strength (10.5 MPa), and higher bonding strength (6.62 kgf/cm<sup>2</sup>) to the steel substrate. Furthermore, acceptable additives to the formulation could enhance its flame-retardancy and increase its mechanical strength as well. Mullite whisker formed from the interaction of wollastonite, aluminum trihydroxide, and aluminum fluoride acts as an outer ceramic shield that enhances mechanical strength and compactness. In addition, Mg-containing minerals with calcium carbonate treated at high temperatures, transform into magnesium calcium carbonate after releasing CO<sub>2</sub>. At the optimum composition of MKPC (magnesia/KH<sub>2</sub>PO<sub>4</sub> molar ratio = 4; wollastonite:vermiculite = 20:10 wt.%; aluminum trihydroxide = 10 wt.%; and calcium carbonate = 5 wt.%), coated on a steel substrate, the flame-resistance limit results exhibit below 200 °C on the back surface of the steel substrate after one hour of flaming (ca. 1000 °C) on the other surface, and the flame-resistance rating results demonstrate only 420 °C on the back surface of the steel substrate after three hours of flaming (>1000 °C) on the other surface. Both requirements for the flame-resistance limit and three-hour flame-resistance rating are met with the optimum compositions, indicating that MKPC plays an effective role in establishing flame-retardancy.https://www.mdpi.com/1996-1944/15/15/5317magnesium potassium phosphate hydrate-based flame-retardant coatingmullite whiskerflame-resistance limitflame-resistance ratingceramic shieldflame-retardancy |
| spellingShingle | Sin-Nan Chen Ching Lin Hao-Lun Hsu Xin-Han Chen Yu-Chang Huang Tar-Hwa Hsieh Ko-Shan Ho Yu-Jun Lin Inorganic Flame-Retardant Coatings Based on Magnesium Potassium Phosphate Hydrate Materials magnesium potassium phosphate hydrate-based flame-retardant coating mullite whisker flame-resistance limit flame-resistance rating ceramic shield flame-retardancy |
| title | Inorganic Flame-Retardant Coatings Based on Magnesium Potassium Phosphate Hydrate |
| title_full | Inorganic Flame-Retardant Coatings Based on Magnesium Potassium Phosphate Hydrate |
| title_fullStr | Inorganic Flame-Retardant Coatings Based on Magnesium Potassium Phosphate Hydrate |
| title_full_unstemmed | Inorganic Flame-Retardant Coatings Based on Magnesium Potassium Phosphate Hydrate |
| title_short | Inorganic Flame-Retardant Coatings Based on Magnesium Potassium Phosphate Hydrate |
| title_sort | inorganic flame retardant coatings based on magnesium potassium phosphate hydrate |
| topic | magnesium potassium phosphate hydrate-based flame-retardant coating mullite whisker flame-resistance limit flame-resistance rating ceramic shield flame-retardancy |
| url | https://www.mdpi.com/1996-1944/15/15/5317 |
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