Formation and structure of the epoxy-silica hybrids

Matějka, Libor; Dušek, Karel; Pleštil, Josef; Křı́ž, Jaroslav; Lednický, F.

doi:10.1016/s0032-3861(98)00214-6

Cited by 151 publications

(105 citation statements)

References 18 publications

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“…In this case, the requirements related to the mechanical properties are often limited. On the contrary, severe regulations about the fire resistance must be respected in order use the materials [7]. As it is known, traditional halogen-based flame retardants are persistent organic pollutants of global concern and generate corrosive/toxic combustion products [8].…”

Section: Introductionmentioning

confidence: 99%

“…In details, the use of coupling agents allows preventing phase separation phenomena of the epoxy and inorganic components, hence giving rise to the formation of silica/ epoxy hybrid networks; therefore, the organic and/or inorganic precursors have to be modified in order to achieve an optimal compatibility between the organic and inorganic components of the resulting hybrid material [16,17]. However, the preparation of epoxy hybrid materials is largely empirical and requires an efficient control of the key parameters for the assembly of the organic and inorganic domains into an optimized morphology.…”

Section: Introductionmentioning

confidence: 99%

“…It is known that the inclusion of silica into epoxy networks favors the char formation and increases its yield, hence improving the thermal stability: in fact, the carbonaceous residue layer acts as a thermal insulator and a barrier to oxygen diffusion [23,24]. Matějka et al [7] investigated the thermal degradation of epoxy/ silica nanocomposites owing to their widespread use as high-performance materials. Thermal analysis results, coming from several experiments [23,24], confirm that silica, being an inherently stable inorganic phase, lowers the degradation rates by favoring the formation of more voluminous and mechanically stronger char; furthermore, it also affects the pyrolytic degradation of amine-cured epoxy networks that proceeds through several overlapping mechanisms, e.g., dehydration, intramolecular cyclization, isomerization, or chain-transfer reactions [25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

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Effects of post cure treatment in the glass transformation range on the structure and fire behavior of in situ generated silica/epoxy hybrids

Bifulco

Tescione

Capasso

et al. 2018

J Sol-Gel Sci Technol

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Effects of post cure treatment in the glass transformation range on the structure and fire behavior of in situ generated silica/epoxy hybrids Abstract A new "in situ" sol-gel synthesis procedure was exploited to produce silica/epoxy nanocomposites with 6 wt.% maximum silica content. 3-Aminopropyltriethoxysilane (APTS) was used as a coupling agent. The experimental results (fouriertransform infrared spectroscopy, FTIR, small-angle X-ray scattering, SAXS, transmission electron microscopy, TEM, nuclear magnetic resonance, NMR, and dynamic mechanical analysis, DMA) support that the structure consists of nanosized silica particles (maximum 1.25 nm in size) embedded in a hybrid co-continuous network. A post cure non-isothermal heating from 15 to 100°C (beyond the Tg of the neat epoxy) caused Tg and storage modulus to increase. The fire behavior, that, owing to severe regulations (i.e., in aerospace engineering), often prevents composites applications, was also studied. The formed silica domains prevented melt dripping phenomena during vertical flame spread tests. Cone calorimetry tests showed a remarkable decrease of the heat release rate (HRR) for all the hybrid systems with respect to the neat cured resin, even at very low silica loadings (i.e., 2 wt.%). This decrease was much more pronounced for the hybrid structures that were not subjected to the post cure thermal treatment. The use of multiple structural investigation techniques allowed to choose among multiple hypothesis and conclude that nanoparticles clustering is the main reason of the effects of the post curing treatments. Graphical Abstract SAXS of the samples before (EPO) and after (EPO_t) post cure thermal treatment in the glass transformation range. Effect of the post cure on the glass transformation temperature (Tg) and heat release rate (HRR) Photos of samples EPO and EPO 2% Si after vertical flame spread tests Highlights• A hybrid co-continuous network embedding nanoparticles (maximum 1.25 nm in size) was obtained;• A post-cure was performed above the glass transformation temperature, T g , of neat epoxy;• The post cure makes T g , storage modulus and Heat Release Rate (HRR) to increase;• No dripping in flame test and up to 40% HRR reduction for only 2 wt.% silica content is observed;• The post cure effects depend on nanoparticles clustering in the glass transformation range.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of post cure treatment in the glass transformation range on the structure and fire behavior of in situ generated silica/epoxy hybrids

Bifulco

Tescione

Capasso

et al. 2018

J Sol-Gel Sci Technol

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“…Silica is considered as the most common inorganic component though many other metal oxides such as titania, boehmite, and zirconia have also been used to reinforce the organic polymers. Some of the important polymers used in preparation of hybrid materials in the recent past have been poly(dimethylsiloxane) [8][9][10][11], epoxies [12][13][14], poly(organophosphazenes) [15,16], polyacrylates [17][18][19], polyimides [20][21][22][23][24][25][26][27] and polyaramids [28][29][30][31][32] and polybenzoxazoles [33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Thermal and mechanical properties of chemically bonded aramid–silica nano-composites

Al‐Sagheer

Ali

Muslim

et al. 2006

Science and Technology of Advanced Materials

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Thermally stable aramid-silica nano-composites have been prepared via the sol-gel process. Two types of aramid matrices were used. Polyamide chains having no pendant hydroxyl groups were prepared by reacting a mixture of 1,3-and 1,4-phenylenediamine in 65:35 mole ratio with equivalent amount of terephthaloyl chloride (TPC) in dimethylacetamide (DMAc) as solvent. The silica network was developed in the matrix by hydrolysis and condensation of various proportions of tetraethoxysilane (TEOS) and this system was used as reference. The matrix having pendant hydroxyl groups was synthesized by the co-polymerization of a mixture of phenylenediamines and 2,4-diaminophenol with equivalent amount of TPC in DMAc. The hydroxyl groups on the chain were reacted with isocyanatopropyltriethoxysilane (ICTOS), which together with TEOS produced silica network structure bonded with the polymer chain. The morphology, thermal and mechanical properties of both types of composites, with and without chemical bonding with silica network have been studied. The glass transition temperature as determined from the maxima of tan d data using dynamic mechanical thermal analysis showed a large increase in case of bonded system in comparison to the unbonded system. The value of the storage modulus was also found to be considerably higher in case of bonded system. The values of thermal expansion coefficient decreased with inclusion of silica in the matrix. The thermal decomposition temperature of these hybrids in air was in the range of 480-500 8C. q

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“…A desordem causada na organização cristalina da argila, devido à entrada das cadeias poliméricas em sua estrutura, aumenta ainda mais este espaçamento, podendo levar à esfoliação das lamelas (Figura 3) [1,2] . organofílica advêm da íntima interface polímero-carga proporcionada pela forte interação em escala nanométrica [8,[13][14][15][16][17] . O emprego de quantidades reduzidas dessas nanocargas sugere preservação das propriedades da matriz polimérica aliada ao ganho em certas características do nanomaterial sobre o polímero puro.…”

Section: Difração De Raios Xunclassified

Investigação da influência do processamento na dinâmica molecular de nanocompósitos de policarbonato e argila organofílica obtidos via intercalação por fusão

et al. 2012

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IntroduçãoNanocompósitos poliméricos vêm ganhando atenção crescente no âmbito da pesquisa mundial nas últimas décadas [1,2] . Os nanomateriais híbridos, formados pela matriz polimérica e uma carga geralmente mineral que apresenta ao menos uma dimensão em escala de ordem nanométrica (10 -9 m), são obtidos tradicionalmente por meio de quatro rotas: método sol-gel, polimerização in situ, intercalação por solução (solution casting) e intercalação no estado fundido [1,[3][4][5] .A intercalação no estado fundido é o método mais rápido dentre os três apresentados para obtenção de nanocompósitos. Além de não utilizar solventes potencialmente nocivos ao meio ambiente e à saúde, tem a vantagem dos nanomateriais assim obtidos poderem ser moldados diretamente em formas específicas para sua aplicação, sem necessidade de processamento adicional [1] .Dentre os vários tipos de nanocompósitos existentes, os formados por polímeros e silicatos lamelares se destacam por suas propriedades mecânicas, sua boa resistência ao calor e à oxidação, transparência óptica e biodegradabilidade, além de apresentarem baixa permeabilidade aos gases [6][7][8][9][10][11] .A argila mais empregada em pesquisa na área de nanocompósitos baseados em polímero-silicatos é a bentonita, pertencente ao grupo das esmectitas. Estas, cujo argilomineral predominante é a montmorilonita, caracterizam-se por possuir estruturas lamelares do tipo 2:1, com duas folhas tetraédricas de sílica e uma folha octaédrica de alumina [1,12] . Estas argilas são modificadas quimicamente de maneira a tornarem-se organofílicas. Este processo envolve a troca dos cátions livres na galeria entre as camadas da argila por sais graxos de amônio quaternário, que são os mais comumente empregados dentre os surfactantes disponíveis [1,2] .As características térmicas, mecânicas, ópticas, elétricas e de barreira apresentadas por nanocompósitos de polímero-argila Resumo: Nanocompósitos baseados em policarbonato e argila organofílica foram obtidos pelo método de intercalação por fusão em câmara de mistura sob diferentes valores de torque e temperatura. A influência desses parâmetros na qualidade da dispersão da argila na matriz polimérica foi investigada por ressonância magnética nuclear (RMN) de baixo campo, empregando o tempo de relaxação longitudinal, T 1 H, e por difração de raios X. As diferenças nos tempos de relaxação longitudinal e nos padrões de difração de raios X foram correlacionadas com a formação de domínios com mobilidades distintas. O nanomaterial formado apresentou morfologia intercalada com afastamento crescente das camadas de argila, conforme as condições de processamento se tornavam mais severas. A RMN 1 H mostrou que tanto o cisalhamento quanto a temperatura afetaram a mobilidade das cadeias poliméricas, explicitando a homogeneidade crescente da distribuição dos domínios de relaxação, de acordo com o aumento do torque e da temperatura. Palavras-chave: Nanocompósito, intercalação por fusão, RMN. On the Influence of Processing Parameters on the Molecular Dynamics of Melt Inter...

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Formation and structure of the epoxy-silica hybrids

Cited by 151 publications

References 18 publications

Effects of post cure treatment in the glass transformation range on the structure and fire behavior of in situ generated silica/epoxy hybrids

Effects of post cure treatment in the glass transformation range on the structure and fire behavior of in situ generated silica/epoxy hybrids

Thermal and mechanical properties of chemically bonded aramid–silica nano-composites

Investigação da influência do processamento na dinâmica molecular de nanocompósitos de policarbonato e argila organofílica obtidos via intercalação por fusão

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