NMR evaluation of montmorillonite's <i>d</i>‐spacings on the formation of phosphocarbonaceous species in intumescent systems

Silva, Ribeiro; Martins, Raíssa Carvalho; Cescon, Leonardo dos Santos; Estevão, Luciana Rocha de Moura; Nascimento, Marco Antônio Chaer; Nascimento, Regina Sandra Veiga

doi:10.1002/app.48053

Cited by 6 publications

(6 citation statements)

References 39 publications

(81 reference statements)

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“…This effect of decreasing the flame retardancy properties with the increase of the d-spacing of the montmorillonite has also been observed for the system containing APP422 and PER (Ribeiro et al, 2013). FTIR and NMR results of burnt residues of the composites containing both APP422/PER and montmorillonite indicated that the increase of the montmorillonite d-spacing leads to a delay in the formation of the phosphocarbonaceous structure and, consequently, to a later char formation (Ribeiro et al, 2013(Ribeiro et al, , 2019, lowering the protection.…”

Section: Flammability Evaluation-loimentioning

confidence: 57%

Microscopy as a tool to investigate the influence of ammonium polyphosphate particle size on the flame retardant properties of polymer composites

Silva

Martins

Estevão

et al. 2019

Microscopy Res & Technique

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The influence of ammonium polyphosphate (APP) particle size on the performance of an intumescent formulation and on the synergistic action of a series of montmorillonite samples with different d‐spacings for the production of flame retardant composites was investigated. The polymer matrix employed was poly(ethylene‐co‐butyl acrylate), EBA 30, and the intumescent formulation consisted of APP and pentaerythritol (PER). After being processed, the composites were submitted to scanning electron microscopy (SEM), thermogravimetric analysis, heating microscopy, and limiting oxygen index tests. The results indicate that the greater interaction between the APP and PER molecules, caused by the increase of the contact area promoted by the reduction of the APP particle size, could favor the esterification reaction between APP423 and PER, allowing the formation of a greater amount of char precursors in shorter period of time. In addition, the montmorillonite d‐spacings had a more pronounced influence on the clays synergistic action with the intumescent formulation containing the APP with smaller particle size. Microscopy has shown to be an important tool to investigate APP particle size effect on the fire retardancy. AFM results enabled the detection of nanometric particles in the sample containing the smallest particle size of APP. SEM micrographs showed that those nanometric particles were better dispersed in the matrix, interacting more effectively with the other components, a factor probably responsible for the superior fire retardancy results. Heating microscopy revealed that the material with smaller APP particle size did show some remaining structure at the temperature of 850°C.

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Section: Flammability Evaluation-loimentioning

confidence: 57%

Microscopy as a tool to investigate the influence of ammonium polyphosphate particle size on the flame retardant properties of polymer composites

Silva

Martins

Estevão

et al. 2019

Microscopy Res & Technique

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“…Considering that the structure of zeolites can collapse at high temperatures and in contact with very acid solutions, it may be suggested that during the formation of the intumescent layer, the destruction of the zeolite crystalline structure occurs due to the production of phosphoric acid, from the thermal decomposition of ammonium polyphosphate, which occurs around 280 • C. Bourbigot et al verified the formation of aluminosilicophosphoric species above 280 • C by 27 Al NMR, which would promote greater thermal stability for the intumescent layer [22]. This type of structure has also been observed in composites of PP + APP/PER + montmorillonite heated at around 280 • C [20]. Therefore, taking into account a possible collapse of the crystalline structure at 280 • C, it is suggested that zeolites should act at first catalyzing the esterification reaction, where the concentration and accessibility of acid sites are determinant, and later in the formation of aluminophosphoric species, increasing the thermal stability of the protective layer.…”

Section: Limiting Oxygen Index (Loi)mentioning

confidence: 92%

“…Several studies have focused on the development of synergistic agents that increase the effectiveness of intumescent formulations, some examples include: organometallic compounds [18], montmorillonite [19][20][21], and zeolites [22,23]. Studies have shown that montmorillonite, faujasite, mordenite and 4A zeolites act as synergistic agent in intumescent formulations, catalyzing the reactions of carbonaceous layer formation and improving the mechanical properties of the protective layer, increasing its thermal stability [12,21].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Application of H-ZSM-5 Zeolites with Different Levels of Acidity as Synergistic Agents in Flame Retardant Polymeric Materials

et al. 2019

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Several studies show a synergistic effect between intumescent formulations and aluminosilicates, such as zeolites and clays, but little is known about the effect of acidity of these additives on the synergistic action. In this work, H-ZSM-5 zeolite was submitted to desilication treatments for 30 min and for 2 h, and silicalite-1 was synthesized. The objective was to obtain samples of equivalent crystalline structure, but with different amounts of acid sites, in order to evaluate the effect of acid concentration of H-ZSM-5 zeolites on the synergistic action with an intumescent formulation composed by ammonium polyphosphate and pentaerythritol in polypropylene. H-ZSM-5 zeolites and silicalite were characterized by X-ray diffraction, nitrogen adsorption analysis and temperature-programmed desorption of ammonia. The desilication produced H-ZSM-5 zeolites with similar volumes of mesopores in both treatments, but the zeolite resulting from 2 h of desilication presented a higher concentration of acid sites than the zeolite from 30 min. The flame-retardant properties were evaluated by UL-94 classification, limiting oxygen index, glow-wire, thermogravimetric analysis and heating microscopy. The results showed that increasing the concentration and accessibility of the acid sites of H-ZSM-5 zeolites the flame-retardant properties of the studied composites improved. It is suggested that the increase of acid site concentration positively influences the catalysis of the reaction between ammonium polyphosphate and pentaerythritol, favoring the production of the precursors of the intumescent layer.

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“…Many works seek to develop more efficient systems by adding aluminosilicate synergistic agents, such as zeolites [13][14][15] and clays [16][17][18][19][20], to the intumescent formulations. Overall, the authors address the synergic effects observed in the formation of aluminophosphate species [21][22][23] that would connect the layers of condensed aromatic rings, enhancing the char flexibility during the swelling process, consequently minimizing the generation of cracks and holes, which are major drawbacks for the efficiency of the intumescent layer at higher temperatures [10,16]. Moreover, the addition of mineral fillers reduces the total amount of combustible material and the rate of diffusion of oxygen into the polymer, by forming an inorganic barrier on the surface of the burning polymer, protecting it from the external heat source [24].…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, only few works investigated the influence of the acidity of aluminosilicates on the flame-retarding properties of intumescent composites [23,[25][26][27][28][29]. Montmorillonites are well-known catalysts for esterification reactions in organic liquid media and many works try to correlate a better catalytic performance to the presence of Brønsted acidic sites [30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Flame-Retarding Properties of Injected and 3D-Printed Intumescent Bio-Based PLA Composites: The Influence of Brønsted and Lewis Acidity of Montmorillonite

et al. 2022

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The influence of processing intumescent bio-based poly(lactic acid) (PLA) composites by injection and fused filament fabrication (FFF) was evaluated. A raw (ANa) and two acidic-activated (AH2 and AH5) montmorillonites were added to the intumescent formulation, composed by lignin and ammonium polyphosphate, in order to evaluate the influence of the strength and the nature (Brønsted or Lewis) of their acidic sites on the fire behavior of the composites. The thermal stability and the volatile thermal degradation products of the composites were assessed. The injected and 3D-printed composites were submitted to cone calorimeter (CC), limit oxygen index (LOI), and UL-94 flammability tests. A similar tendency was observed for the injected and 3D-printed samples. The high density of strong Lewis sites in AH2 showed to be detrimental to the fire-retarding properties. For the CC test, the addition of the intumescent composite reduced the peak of heat released (pHRR) in approximately 49% when compared to neat PLA, while the composites containing ANa and AH5 presented a reduction of at least 54%. However, the addition of AH2 caused a pHRR reduction of around 47%, close to the one of the composite without clay (49%). In the LOI tests, the composites containing ANa and AH5 achieved the best results: 39% and 35%, respectively, for the injected samples, and 35 and 38% for the 3D-printed samples. For the composite containing AH2 the LOI values were 34% and 32% for injected and 3D-printed samples, respectively. Overall, the best performance in the flammability tests was achieved by the composites containing clays with only weak and moderate strength acidic sites (ANa and AH5).

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NMR evaluation of montmorillonite's d‐spacings on the formation of phosphocarbonaceous species in intumescent systems

Cited by 6 publications

References 39 publications

Microscopy as a tool to investigate the influence of ammonium polyphosphate particle size on the flame retardant properties of polymer composites

Microscopy as a tool to investigate the influence of ammonium polyphosphate particle size on the flame retardant properties of polymer composites

Synthesis and Application of H-ZSM-5 Zeolites with Different Levels of Acidity as Synergistic Agents in Flame Retardant Polymeric Materials

Flame-Retarding Properties of Injected and 3D-Printed Intumescent Bio-Based PLA Composites: The Influence of Brønsted and Lewis Acidity of Montmorillonite

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