SYNTHESIS AND CHARACTERIZATION OF MAGNESIUM TETRABORATE-BASED MULTIFUNTIONAL FLAME RETARDANTS AND THEIR APPLICATION FOR FLAME RETARDANCY OF POLYURETHANE

Date

2024-3-03

Author

Çelik, Muzaffer Gençay

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Boron compounds have low toxicity and diverse molecular structures, making them effective flame-retardant additives in polymer-based materials with various mechanisms of action. These additives are used alone or in combination with mineral fillers, intumescent systems, phosphorus, halogen, nitrogen, silicon, and carbon-containing additives. In this research, four different boron-containing materials such as magnesium tetraborate (MTB), magnesium tetraborate-hydroxyapatite core/shell (MTB@HAp), and melamine formaldehyde (MF) resin-encapsulated MTB and MF encapsulated MTB@HAp, used to improve the flame retardancy of polyurethane (PU). MTB is synthesized using the solid-state synthesis method. HAp coated MTB is prepared using the wet precipitation method. To enhance the flame retardancy performance of MTB, a combination of boron-based and nitrogen-based compounds, such as MF, can provide synergy. The novel MF microcapsulated MTB-MF and MTB@HAp with a double shell are prepared by in situ polymerization. The synthesized MTB-based materials are characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimeter (DSC). Polyurethane composites containing MTB, MTB@HAp, MTB-MF, and MTB@HAp-MF with varying amounts were produced by isocyanate and polyether polyol reaction. The flame-retardant action of MTB, MTB@HAp, MTB-MF, and MTB@HAp-MF in PU are studied using Limiting Oxygen Index (LOI) and standard test method for measuring the comparative burning characteristics of solid plastics in a vertical position (UL-94V), Mass Loss Calorimeter (MLC) and TGA. In addition, the thermal behaviors of PU composites are characterized by TGA and TGA coupled FTIR and the morphologies of residues are investigated with Scanning Electron Microscopy (SEM). Results show that 10PHR-MTB and 15PHR-MTB@HAp core shell containing PU composites achieved 25% and 26.5% LOI values with V-2 of UL-94 rating, respectively. Besides, the peak Heat Release Rate of 10PHR-MTB and 15PHR-MTB@HAp containing PU composites were reduced by 28% and 20% with respect to the PHRR of neat PU. 5PHR-MTB-MF microcapsule (the mass ratio of MTB:MF-1:3) achieved the maximal LOI value of 27%, V-0 of UL-94 rating, and significantly decreased the peak heat release rate from 350 kW/m2 to 70 kW/m2 with respect to pure PU. The present work demonstrates MF microcapsules prepared with efficiency exhibit remarkable flame retardancy, making them a promising multifunctional composite for usage as a flame retardant in polyurethane applications.

Subject Keywords

Thermoset Polyurethane Flame Retardancy, Magnesium Tetraborate, Melamine Formaldehyde Resin Microencapsulation, Magnesium Tetraborate Hydroxyapatite Core Shell, Flame Retardancy Mechanism.

URI

https://hdl.handle.net/11511/109213

Collections

Graduate School of Natural and Applied Sciences, Thesis