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Abstract  

The hydrolytic condensation of a precursor synthesized by the reaction of equimolar amounts of (3-aminopropyl)triethoxysilane and phenylglycidylether led to a distribution of polyhedral oligomeric silsesquioxanes (POSS) containing 8–11 Si atoms, functionalized with amine groups. About 57% of the NH functionalities were active for reaction with epoxy groups. The multifunctional amine-POSS was used to modify an epoxy network obtained by the homopolymerization of diglycidylether of bisphenol A initiated by benzyldimethylamine. The main effect of POSS modification was an increase in both the glassy and rubbery modulus explained, respectively, by the increase in cohesive energy and crosslink densities.

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Journal of Thermal Analysis and Calorimetry
Authors: I. Blanco, L. Abate, F. A. Bottino, and P. Bottino

past to prepare organic–inorganic hybrid systems [ 5 – 14 ], but, in the last years, another class of nanoparticles, polyhedral oligomeric silsesquioxanes (POSSs), has awaken an increasing interest for the formulation of nanocomposites [ 15 – 21

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Introduction Incompletely condensed polyhedral oligomeric silsesquioxanes (POSS) are a class of three dimensional oligomeric organosilicon compounds with cage-like framework (ca. 1.5–2.0 nm) possessing different degrees of

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, combined with good polymer–particle interfacial adhesion, eliminates scattering and allows for the exciting possibility of developing strong yet transparent films, coatings and membranes [ 9 – 11 ]. Polyhedral oligomeric silsesquioxanes (POSSs) are

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Journal of Thermal Analysis and Calorimetry
Authors: C. Ramírez, M. Rico, J. M. L. Vilariño, L. Barral, M. Ladra, and B. Montero

Summary Cubic silsesquioxanes offer access to organic/inorganic hybrids. A system formed by a polyhedral oligomeric silsesquioxane (POSS) with eight epoxy reactive groups per molecule, octaepoxycyclohexyldimethylsilyl-POSS, cured with an aliphatic diamine (bisaniline) was studied in different ratios. The characterization of the POSS was carried out by differential scanning calorimetry (DSC) and thermogravimetry (TG). The distribution of species in the reaction of the mixtures POSS/diamine was followed by gel permeation chromatography (GPC). The degradation was studied by thermogravimetric analysis.

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Abstract  

We have used molecular simulations to study the properties of nanocomposites formed by the chemical incorporation of polyhedral oligomeric silsesquioxane (POSS) particles in the cross-linked epoxy network. The particular POSS molecule chosen—glycidyloxypropyl-heptaphenyl POSS—can form only one bond with the cross-linker and thus was present as a dangling unit in the network. Four epoxy-POSS nanocomposites containing different fractions (up to 30 mass/%) of POSS particles were studied in this work. Well-relaxed atomistic model structures of the nanocomposites were created and then molecular dynamics simulations were used to characterize the density, glass transition temperature (T g), and the coefficient of volume thermal expansion (CVTE) of the systems. In addition to the effect of nanoparticle loading, the effect of nanoparticle chemistry on the nanocomposite properties was also characterized by comparing these results with our previous results (Lin and Khare, Macromolecules 42:4319–4327, 2009) on neat cross-linked epoxy and a nanocomposite containing a POSS nanoparticle that formed eight bonds with the cross-linked network. Our results showed that incorporation of these monofunctional POSS particles into cross-linked epoxy does not cause a measurable change in its density, glass transition temperature, or the CVTE. Furthermore, simulation results were used to characterize the aggregation of POSS particles in the system. The nanofiller particles in systems containing 11, 20, and 30 mass/% POSS were found to form small clusters. The cluster-size distribution of nanoparticles was also characterized for these systems.

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Abstract  

Organic–inorganic hybrid composites of epoxy and phenyltrisilanol polyhedral oligomeric silsesquioxane (Ph7Si7O9(OH)3, POSS-triol) were prepared via in situ polymerization of epoxy monomers. The nanocomposites of epoxy with POSS-triol can be prepared in the presence of metal complex latent catalyst, aluminum triacetylacetonate ([Al]) for the reaction between POSS-triol and diglycidyl ether of bisphenol A (DGEBA). The dispersion morphology of organic–inorganic hybrid was characterized by scanning electronic microscopy (SEM). The thermostability of composites was evaluated by thermal gravimetric (TG) analysis. The flammability was evaluated by cone calorimeter test. The presence of [Al] latent catalyst leads to a decrease in combustion rate with respect to epoxy and epoxy/POSS composites as well as reduction in smoke, CO and CO2 production rate. The effect of [Al] is to reduce the size of spherical POSS particles from 3–5 μm in epoxy/POSS to 0.5 μm in epoxy/POSS[Al]. Furthermore, POSS with smaller size may form compact and continue char layer on the surface of composites more efficiently.

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Abstract  

The thermal behaviour of an epoxy resin cured with an amine-POSS was studied using differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The kinetic of polymerization reaction and the thermal degradation have been analyzed based on an iso-conversional model. The obtained results showed that the activation energies of both processes depend on the degree of conversion.

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Journal of Thermal Analysis and Calorimetry
Authors: M. Villanueva, J. Martín-Iglesias, J. Rodríguez-Añón, and J. Proupín-Castiñeiras

Abstract  

The thermal degradation of the epoxy system diglycidyl ether of bisphenol A (DGEBA n=0) and m-xylylenediamine (mXDA) containing different concentrations of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles was studied by thermogravimetric analysis in order to determine the influence of both, the POSS concentration and the curing cycle on the degradation process and to compare it with the results for the non modified system. Glass transition temperatures for the same systems were also determined by differential scanning calorimetry. Different behaviors have been observed, depending on the POSS concentration and on the curing selection.

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