Mechanistic Aspects of Condensed- and Gaseous-Phase Activities of Some Phosphorus-Containing Fire Retardants
Abstract
:1. Introduction
2. Materials and Methods
3. Results and Discussion
3.1. Condensed-Phase Analysis
3.1.1. Inductively-Coupled Plasma Optical Emission Spectroscopy (ICP-OES)
3.1.2. Solid-State NMR Spectra
3.1.3. Raman Spectroscopy
3.2. Vapour-Phase Analyses of the Additives (i.e., Hyphenated Techniques)
3.2.1. Gas Chromatography-Mass Spectrometry (GC/MS)
3.2.2. Pyrolysis-Gas Chromatography/Mass Spectrometry (Pyrolysis-GC/MS)
4. Conclusions
- The inorganic solid additive, i.e., (NH4)2HPO4, underwent a two-step degradation, yielding ammonia gas and phosphoric acid in the first step, followed by the degradation of the product, ammonium dihydrogen phosphate to produce oxides of phosphorus and nitrogen and ammonia;
- As expected, the liquid additives, owing to their volatility as compared to the solid ones, showed a higher presence in the vapour phase. Furthermore, it can be seen that relatively substantial amounts of phosphorus-containing species from phosphine and the phosphine oxides were also presumably released into the vapour phase through fragments emanating from the thermal pyrolysis in the condensed phase
- The 31P-NMR spectra showed the ‘phosphorus’ acid species (∂ ~ 0 ppm), or oligomeric phosphate moieties (∂ ~ −10 ppm), are generated from the initial cracking/condensation reactions of AP, DEPi, TEPi, TEPa, DEPP and DEBP. However, cracking of TPP, TPPO and DOPO are bound to produce phenyl, or biphenyl species, and the phosphorus atom is likely to go into vapour phase either in the elemental form and/or as oxide species;
- The Raman spectra exhibited different degrees of graphitization, as revealed by the varying ratios of the areas corresponding to ordered and amorphous domains;
- From the complementary information that was gathered though vapour analyses, some probable mechanistic pathways that underpin the condensed- and gaseous-phase activities of the different additives were suggested
- In summary, it can be inferred that the organic solid additives (TPP, TPPO and DOPO) are predominantly active in the vapour phase, whereas the liquid additives (DEPi, TEPi, TEPa, DEPP and DEBP) can considered as more active in the condensed phase. The inorganic additive, AP, can assumed to be more active in the condense phase just the liquid additives.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Sl. No. | Sample | wt % P in the Coating | Char Yield (wt %) from Cone | Theoretical Maximum of P Loading in the Char (wt %) | P Loading (ppm) | wt % P in the Char | wt % of P in the Gaseous Phase |
---|---|---|---|---|---|---|---|
1 | Fish gelatin + AP | 4.10 | 21 | 19.52 | 36.6 | 7.82 | 59.93 |
2 | Fish gelatin + DOPO | 3.68 | 23 | 16.00 | 24.45 | 6.06 | 62.12 |
3 | Fish gelatin + TPP | 3.48 | 20 | 17.40 | 14.73 | 4.46 | 74.36 |
4 | Fish gelatin + TPPO | 3.43 | * --- | * --- | 11.23 | 3.50 | * --- |
5 | Fish gelatin + DEPi | 4.05 | 20 | 20.25 | 9.02 | 4.68 | 76.89 |
6 | Fish gelatin + TEPi | 3.97 | 21 | 18.90 | 3.84 | 2.83 | 85.02 |
7 | Fish gelatin + TEPa | 3.62 | 21 | 17.24 | 2.15 | 3.16 | 81.67 |
8 | Fish gelatin + DEPP | 3.85 | 19 | 20.26 | 4.63 | 2.04 | 89.93 |
9 | Fish gelatin + DEBP | 3.63 | 20 | 18.15 | 1.68 | 1.85 | 89.80 |
Sl. No. | Additive | ∂ Value for 31P of the Additives * (Solution-State) | ∂ Value for 31P of the Char Residue # |
---|---|---|---|
1 | AP | 0.02 | −2.3 (−13.4) |
2 | TPP | −7.10 | 2.9 (−8.5) |
3 | TPPO | 27.6 | 2.9 (−8.5) |
4 | DOPO | 16.7 | −1.3 (−9.8) |
5 | DEPi | 7.30 | −2.3 (−13.1) |
6 | TEPi | 7.30 | −3.3 (−15.0) |
7 | TEPa | −1.00 | −2.6 (−10.8) |
8 | DEPP | 32.2 | −1.3 (−9.1) |
9 | DEBP | 26.4 | −1.0 (−10.8) |
Sl. No. | Char Residue | Intensity of the G Band (IG) | Intensity of the D Band (ID) | Ratio (IG/ID) |
---|---|---|---|---|
1 | Unprotected wood | 18,030 | 24,830 | 0.73 |
2 | Fish gelatin + AP | 21,850 | 30,360 | 0.72 |
3 | Fish gelatin + TPP | 476,979 | 1,099,132 | 0.43 |
4 | Fish gelatin + TPPO | 450,413 | 343,278 | 1.32 |
5 | Fish gelatin + DOPO | 648,452 | 1,030,772 | 0.63 |
6 | Fish gelatin + DEPi | 580,753 | 1,002,797 | 0.58 |
7 | Fish gelatin + TEPi | 515,705 | 954,779 | 0.54 |
8 | Fish gelatin + TEPa | 570,280 | 943,631 | 0.60 |
9 | Fish gelatin + DEPP | 402,813 | 1,238,529 | 0.33 |
10 | Fish gelatin + DEBP | 846,410 | 913,333 | 0.93 |
Sample | Chemical Structures | Retention Time (min) | Molar Mass | [M]+. | [M ± 1]+. | [M] (100%) | Other Predominant Species/Remarks |
---|---|---|---|---|---|---|---|
DEPi | | 4.7 | 138 | --- | 139 | 83 | 111 |
TEPi | | 3.9 | 166 | 166 | --- | 65 | 139 |
TEPa | | 5.2 | 182 | --- | 183 | 99 | 127 |
DEPP | | 5.0 | 180 | --- | --- | 125 | 43 |
DEBP | | 8.0 | 228 | --- | --- | 91 | 118 |
Sample (Chemical Name) | Chemical Structures | mp/bp (°C) | Pyrolysis Temp. (°C) | Retention Time (min) | Molar Mass | [M]+ ± 1 |
---|---|---|---|---|---|---|
TPP | | 80/377 | 288 | 18.8 | 263 | 262 |
TPPO | | 154–158/360 | 340 | 21.4 | 278 | 277 |
DOPO | | 116–120/200 (at 1mm Hg) | 381 | 18.8 * 15.7/ # 13.1 | 216 | 216 |
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Thomas, A.; Arun, M.; Moinuddin, K.; Joseph, P. Mechanistic Aspects of Condensed- and Gaseous-Phase Activities of Some Phosphorus-Containing Fire Retardants. Polymers 2020, 12, 1801. https://doi.org/10.3390/polym12081801
Thomas A, Arun M, Moinuddin K, Joseph P. Mechanistic Aspects of Condensed- and Gaseous-Phase Activities of Some Phosphorus-Containing Fire Retardants. Polymers. 2020; 12(8):1801. https://doi.org/10.3390/polym12081801
Chicago/Turabian StyleThomas, Ananya, Malavika Arun, Khalid Moinuddin, and Paul Joseph. 2020. "Mechanistic Aspects of Condensed- and Gaseous-Phase Activities of Some Phosphorus-Containing Fire Retardants" Polymers 12, no. 8: 1801. https://doi.org/10.3390/polym12081801