Neste trabalho, foram sintetizados poliuretanos termoplásticos (TPU) via solução em reator e via extrusão reativa em extrusora dupla rosca. Os TPUs foram obtidos com o uso de pré-polímero 4,4‟-difenilmetano (MDI) e poliol poliéster, a hidroquinona bis-2-(hidróxietil)-éter (HQEE), e o n-fenilaminopropil-POSS. Os reagentes e produtos foram caracterizados através de análises de Espectroscopia no Infravermelho com Transformada de Fourier (FTIR), Calorimetria Diferencial de Varredura (DSC), análise Termogravimétrica (TGA) e reometria capilar (exclusivamente para os produtos). As análises de DSC mostraram que a presença do POSS influenciou a entalpia de fusão (ΔHm) dos TPUs sintetizados via solução. As amostras polimerizadas por extrusão reativa a 80 ºC apresentam Tm comparativamente menores que as amostras sintetizadas a 90 ºC, porém com ΔHm superior, indicando que a temperatura possivelmente favorece a formação de um número maior de cristais com um tamanho médio inferior. Também foram observados fenômenos exotérmicos durante o aquecimento das amostras sintetizadas via extrusão reativa, provavelmente devido a disponibilidade de grupos isocianato livres, detectados via FTIR, na região de ~2253 cm-1. A estabilidade térmica dos TPUs via solução também foi alterada pela adição de POSS, enquanto o polímero obtido através da extrusão reativa apresentou valores mais elevados no início da degradação. Os ensaios de TGA em isoterma apresentaram valores de perda de massa progressivamente inferiores nas amostras sintetizadas via extrusão reativa, demonstrando que tanto o POSS quanto a temperatura de síntese influem nas propriedades do polímero. Ensaios de resistência térmica nas amostras apresentaram perdas de massa inferiores nas amostras vi8a xetrusão reativa. Em ensaios de reometria capilar, a inserção do POSS levou a um aumento progressivo da viscosidade intrínseca do polímero, indicando aumento da massa molar média do TPU sintetizado via solução. Os mesmos ensaios executados com as amostras via extrusão reativa mostraram viscosidades aparentes similares, provavelmente influenciados por processos de degradação do material na célula de carga, levando a comportamentos de viscosidade sem uma tendência observável. / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-03T18:10:51Z No. of bitstreams: 1 Dissertacao Gabriel Hoyer Lopes.pdf: 2245249 bytes, checksum: 97ec28c68a7d73e9ca22b258465c50c6 (MD5) / Made available in DSpace on 2014-06-03T18:10:51Z (GMT). No. of bitstreams: 1 Dissertacao Gabriel Hoyer Lopes.pdf: 2245249 bytes, checksum: 97ec28c68a7d73e9ca22b258465c50c6 (MD5) / In this work, thermoplastic polyurethanes (TPU) were synthesized in solution process and reactive extrusion in twin-screw extruder. The TPUs were obtained with the use of pre-polymer based on 4,4´-Methylenediphenyl diisocyanate (MDI) and a polyester functionalized polyol, the bis-2-(hidroxyethyl)ether hidroquinone and the n-phenylaminopropyl-POSS as a second chain extender. The reagents and products were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and also capillary rheometry (only for those products). The DSC analysis presence influenced the melting enthalpy (ΔHm) of the TPU synthesized by solution. The samples synthesized through reactive extrusion at 80 ºC presented a higher Tm compared to the 90 ºC TPUs, with a higher ΔHm, suggesting that the temperature favors the formation of a greater number of crystals with a lower medium size. Exothermic phenomena were observed during the heating of samples synthesized in reactive extrusion, probably due to the availability of free isocyanate groups, which were detected by FTIR in the ~2253 cm-1 region. The thermal stability of the TPUs was enhanced by the addition of POSS, while the polymers obtained through reactive extrusion presented higher onset degradation temperatures. The TGA analysis in isothermal conditions showed progressively lower mass loss values in samples obtained by reactive extrusion, demonstrating that the amount of POSS, as well the synthesis temperature, had influence in the final properties of the TPU. The thermal resistance of samples polymerized in reactive extrusion. In capillary rheometry tests, the insertion of POSS in the polymer led to a progressively higher value of intrinsic viscosity of the TPUs, indicating an increase in the mean molar mass of the TPUs obtained through solution synthesis. The same method was applied to the samples obtained through reactive extrusion, which showed similar apparent viscosities, yet the analysis was probably influenced by the degradation of the TPU inside the loading cell, leading to no measurable tendency in the viscosity of the polymer.

Neste trabalho, foram sintetizados poliuretanos termoplásticos (TPU) via solução em reator e via extrusão reativa em extrusora dupla rosca. Os TPUs foram obtidos com o uso de pré-polímero 4,4‟-difenilmetano (MDI) e poliol poliéster, a hidroquinona bis-2-(hidróxietil)-éter (HQEE), e o n-fenilaminopropil-POSS. Os reagentes e produtos foram caracterizados através de análises de Espectroscopia no Infravermelho com Transformada de Fourier (FTIR), Calorimetria Diferencial de Varredura (DSC), análise Termogravimétrica (TGA) e reometria capilar (exclusivamente para os produtos). As análises de DSC mostraram que a presença do POSS influenciou a entalpia de fusão (ΔHm) dos TPUs sintetizados via solução. As amostras polimerizadas por extrusão reativa a 80 ºC apresentam Tm comparativamente menores que as amostras sintetizadas a 90 ºC, porém com ΔHm superior, indicando que a temperatura possivelmente favorece a formação de um número maior de cristais com um tamanho médio inferior. Também foram observados fenômenos exotérmicos durante o aquecimento das amostras sintetizadas via extrusão reativa, provavelmente devido a disponibilidade de grupos isocianato livres, detectados via FTIR, na região de ~2253 cm-1. A estabilidade térmica dos TPUs via solução também foi alterada pela adição de POSS, enquanto o polímero obtido através da extrusão reativa apresentou valores mais elevados no início da degradação. Os ensaios de TGA em isoterma apresentaram valores de perda de massa progressivamente inferiores nas amostras sintetizadas via extrusão reativa, demonstrando que tanto o POSS quanto a temperatura de síntese influem nas propriedades do polímero. Ensaios de resistência térmica nas amostras apresentaram perdas de massa inferiores nas amostras vi8a xetrusão reativa. Em ensaios de reometria capilar, a inserção do POSS levou a um aumento progressivo da viscosidade intrínseca do polímero, indicando aumento da massa molar média do TPU sintetizado via solução. Os mesmos ensaios executados com as amostras via extrusão reativa mostraram viscosidades aparentes similares, provavelmente influenciados por processos de degradação do material na célula de carga, levando a comportamentos de viscosidade sem uma tendência observável. / In this work, thermoplastic polyurethanes (TPU) were synthesized in solution process and reactive extrusion in twin-screw extruder. The TPUs were obtained with the use of pre-polymer based on 4,4´-Methylenediphenyl diisocyanate (MDI) and a polyester functionalized polyol, the bis-2-(hidroxyethyl)ether hidroquinone and the n-phenylaminopropyl-POSS as a second chain extender. The reagents and products were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and also capillary rheometry (only for those products). The DSC analysis presence influenced the melting enthalpy (ΔHm) of the TPU synthesized by solution. The samples synthesized through reactive extrusion at 80 ºC presented a higher Tm compared to the 90 ºC TPUs, with a higher ΔHm, suggesting that the temperature favors the formation of a greater number of crystals with a lower medium size. Exothermic phenomena were observed during the heating of samples synthesized in reactive extrusion, probably due to the availability of free isocyanate groups, which were detected by FTIR in the ~2253 cm-1 region. The thermal stability of the TPUs was enhanced by the addition of POSS, while the polymers obtained through reactive extrusion presented higher onset degradation temperatures. The TGA analysis in isothermal conditions showed progressively lower mass loss values in samples obtained by reactive extrusion, demonstrating that the amount of POSS, as well the synthesis temperature, had influence in the final properties of the TPU. The thermal resistance of samples polymerized in reactive extrusion. In capillary rheometry tests, the insertion of POSS in the polymer led to a progressively higher value of intrinsic viscosity of the TPUs, indicating an increase in the mean molar mass of the TPUs obtained through solution synthesis. The same method was applied to the samples obtained through reactive extrusion, which showed similar apparent viscosities, yet the analysis was probably influenced by the degradation of the TPU inside the loading cell, leading to no measurable tendency in the viscosity of the polymer.

No description available.

Polymer electrolyte membrane fuel cells (PEMFCs) are one of the most promising clean technologies under development. However, the main obstacles for commercialising PEMFCs are largely attributed to the technical limitations and cost of current PEM materials such as Nafion. Novel poly(2,5-benzimidazole) (ABPBI)/POSS based polymer composite electrolyte membranes with excellent mechanical and conductivity properties were developed in this project including (I) ABPBI, polybenzimidazole (PBI) and their copolymers were synthesised by solution polymerisation and their chemical structures were confirmed by FTIR and elemental analysis. ABPBI/ActaAmmonium POSS (ABPBI/AM) and ABPBI/TriSilanolPhenyl POSS (ABPBI/SO) composites were also synthesised in situ. High quality polymer and composite membranes were fabricated by a direct cast method; and (II) The mechanical and thermal properties, microstructure and morphology, water and H3PO4 absorbility and proton conductivity of phosphoric acid doped and undoped ABPBI and ABPBI/POSS composite membranes were investigated. SEM/TEM micrographs showed that a uniform dispersion of POSS nano particles in ABPBI polymer matrix was achieved. The best performances on both mechanical properties and proton conductivities were obtained from the ABPBI/AM composite membrane with 3 wt% of POSS (ABPBI/3AM). It was found that both the water and H3PO4 uptakes were increased significantly with the addition of POSS due to formation of hydrogen bonds between the POSS and H2O/H3PO4, which played a critical role in the improvement of the conductivity of the composite membranes at temperatures over 100oC. ABPBI/3AM membranes with H3PO4 uptake above 117% showed best proton conductivities at both hydrous and anhydrous conditions from room temperature to 160oC, which is comparable with the conductivity of commercial Nafion 117 at 20oC in water-saturated condition, indicating that these composite membranes could be excellent candidates as a polymer electrolyte membrane for high temperature applications. A new mechanism for illustrating the improved proton conductivity of composite membranes was also developed.

No description available.

Une série de composant hybride basée sur réactives polyédriques oligomères silsesquioxane (POSS) precusors et ses copolymères réactifs de PGMA ont été synthétisés et utilisés pour nanobuild en époxy. POSS réactifs et de copolymères en dispersion dans la matrice homogène dans, au délà de POSS-POSS interaction, ce qui a entraîné la séparation de phase macroscopique. Les nanocomposites obtenus ont été analysés par microscopie électronique à balayage, microscopie électronique à transmission, diffusion des rayons X et l'analyse mécanique dynamique. Un analogue de POSS (notée POSSMOCA) a été synthétisé par réaction d'addition, qui a réactive liaison groupe amino dans le réseau époxy et d'améliorer la stabilité thermique, en raison du silicium, d'azote et un atome d'halogène structurel. Époxy / polyédriques silsesquioxanes oligomères (POSS) composites hybrides ont été préparés à partir de pré-réaction entre l'éther de silanol POSS-OH et diglycidylique trifonctionnel de bisphénol A (DGEBA) par l'intermédiaire du silanol et un groupe oxiranne. Réactif POSS-PGMA a été polymérisé par polymérisation par transfert de réversible par addition-fragmentation. Il est facile à queue de la compatibilité du copolymère séquencé époxyde avec une matrice de l'étape de croissance-polymérisé, pour former par réaction avec nanostructure segements PGMA. Dans le cas d'inertes POSS-PMMA copolymères modifiés époxy, topologie de copolymère défini la morphologie finale et l'interaction entre époxy et entre eux, en raison de la liaison hydrogène directionnelle à effet de dilution. Tg de conversion époxyde différente, obéi de Gordon-Taylor équation et l'équation Kwei, k qui reflète l'interaction de modificateur et les oligomères DGEBA / MEDA et époxy / amine, était cohérente de la rhéologie et les résultats dynamiques. / A series of hybrid component based on reactive polyhedral oligomeric silsesquioxane(POSS) precusors and its reactive copolymers of PGMA were synthesized and utilized to nanobuild in epoxy. Reactive POSS and copolymer dispersed in homogenous in matrix, overcomed POSS-POSS interaction, which resulted in macroscale phase separation. The nanocomposites obtained were analyzed by Scanning electron microscopy, Transmission electron microscopy, X-ray scattering and dynamic mechanical. An analogue of POSS (denoted as POSSMOCA) was synthesized via addition reaction, which had reactive amino group bonding into epoxy network and improved the thermostability, because of the structural silicon, nitrogen and halogen. Epoxy/polyhedral oligomeric silsesquioxanes (POSS) hybrid composites were prepared from prereaction between trifunctional silanol POSS-OH and diglycidyl ether of bisphenol A (DGEBA) via silanol and the oxirane group. Reactive POSS-PGMA was polymerized via Reversible addition-fragmentation transfer polymerization. It was easy to tail the compatibility of the epoxide block copolymer with a step-growth polymerized matrix, to form nanostructure via reaction with PGMA segements. In the case of inert POSS-PMMA copolymers modified epoxy, topology of copolymer defined the final morphology and interaction between epoxy and them, because of directional hydrogen bonding and dilution effect. Tg of different epoxide conversion, obeyed of Gordon-Taylor equation and Kwei equation, k which reflected the interaction of modifier and DGEBA/MEDA and epoxy/amine oligomers, was consistent of the rheology and dynamic results.

A study has been undertaken with the aim of preparing appropriately functionalised polyhedral oligomeric silsesquioxane (POSS) compounds to be used in ambient-cure chemistry. Numerous epoxy-functionalised compounds have been designed and synthesised and these materials have been characterised in order to determine their chemical structure. These compounds have also been incorporated into existing polymerisation reactions to test whether these materials could be used in the protective coatings industry. A glycidyl-functionalised POSS compound was prepared and reacted with a series of amines to produce ambient-cured polymers which could be used in the coatings industry. There were also a series of experiments undertaken on these polymers to identify the processes at work and to test how they compare to industry standards. As a direct comparator to this work, another set of results was obtained with a cyclic-siloxane material incorporated into the systems in place of the POSS. A linear analogue was also tested. The reactions proved to be a success and an appropriate data-set was yielded. During the synthesis of POSS precursors there are a series of residual materials produced. These materials have also been studied in this project. It was anticipated that these would behave in a similar way to the POSS compounds however the same functionality was never achieved as had been with the POSS. Ambient-cured polymers have also been targeted from a basic hydride-functionalised POSS compound and a polybutadiene system. The appropriate reactions unfortunately never took place as anticipated but there were a series of tests undertaken to identify the processes at work. A study has also been undertaken using near-I.R. to track the curing reactions. From this data, the extent of cure could be studied and the make-up of the reaction could be investigated in more detail.

A series of hybrid component based on reactive polyhedral oligomeric silsesquioxane(POSS) precusors and its reactive copolymers of PGMA were synthesized and utilized to nanobuild in epoxy. Reactive POSS and copolymer dispersed in homogenous in matrix, overcomed POSS-POSS interaction, which resulted in macroscale phase separation. The nanocomposites obtained were analyzed by Scanning electron microscopy, Transmission electron microscopy, X-ray scattering and dynamic mechanical. An analogue of POSS (denoted as POSSMOCA) was synthesized via addition reaction, which had reactive amino group bonding into epoxy network and improved the thermostability, because of the structural silicon, nitrogen and halogen. Epoxy/polyhedral oligomeric silsesquioxanes (POSS) hybrid composites were prepared from prereaction between trifunctional silanol POSS-OH and diglycidyl ether of bisphenol A (DGEBA) via silanol and the oxirane group. Reactive POSS-PGMA was polymerized via Reversible addition-fragmentation transfer polymerization. It was easy to tail the compatibility of the epoxide block copolymer with a step-growth polymerized matrix, to form nanostructure via reaction with PGMA segements. In the case of inert POSS-PMMA copolymers modified epoxy, topology of copolymer defined the final morphology and interaction between epoxy and them, because of directional hydrogen bonding and dilution effect. Tg of different epoxide conversion, obeyed of Gordon-Taylor equation and Kwei equation, k which reflected the interaction of modifier and DGEBA/MEDA and epoxy/amine oligomers, was consistent of the rheology and dynamic results.

As resinas termorrígidas são uma classe de polímeros que devido à reação de reticulação deveriam apresentar uma única cadeia molecular de peso infinito, no entanto, questionamentos sugerem que a formação da rede tridimensional é não-homogênea. Atualmente, devido aos avanços obtidos pela nanotecnologia, torna-se possível uma abordagem diferenciada na modificação química de polímeros como a resina epoxídica. Neste trabalho, foram preparados nanocompósitos adicionando diferentes teores do oligômero poliédrico de silsesquioxano (POSS) n-fenilaminopropil na resina epoxídica. Foi substituindo 1, 5 e 10 por cento em massa (% m.) do agente de reticulação trietilenotetramina (TETA) por POSS. Esta modificação foi realizada com o objetivo de promover maior concentração de interligações nas interfaces das regiões nodulares, descritas como imperfeições ou descontinuidades que ocorrem pela cura não-homogênea da resina. Através da morfologia e da análise do teor de gel, foi evidenciada boa dispersão e melhoria na homogeneidade da rede tridimensional da resina acima de 5 % m. de POSS e aumento da fração gel nos nanocompósitos comparados com a resina epoxídica pura. Na realização de análises de difração de raio-x (DRX) foi visto que a adição do POSS aumentou a distância média entre as cadeias da resina. Foi realizada análise dinâmico-mecânica (DMA) no modo não-isotérmico e por varredura de frequência no modo isotérmico. Pelo modo não-isotérmico os resultados demonstraram que o POSS deslocou a Tg para temperaturas maiores e não alterou significativamente a densidade de ligações cruzadas da resina epoxídica. O modo isotérmico foi utilizado para a determinação de parâmetros das equações de Williams-Landel-Ferry (WLF) e Vogel-Fulcher-Tammann (VFT). Foi calculada a distribuição dos espectros de relaxação H(t) e retardação L(t) molecular através dos módulos de armazenamento e perda obtidos pelo modo isotérmico no DMA. Os parâmetros WLF e VFT demonstraram que a incorporação do POSS ao mesmo tempo em que aumentou a Tg, reduziu a energia de ativação de movimentação segmentar e tornou a resina epoxídica mais forte estruturalmente. A redução da energia de ativação foi associada com a redução das forças de interação intermolecular, enquanto que a redução da fragilidade foi associada ao fato do POSS ser capaz de interligar as interfaces de regiões nodulares. Os espectros H(t) e L(t) mostraram que o pico de relaxação associado aos nódulos formados no processo de reticulação desapareceu. A determinação da capacidade calorífica (Cp) e do excesso de entropia (Sex) através de análises de calorimetria exploratória diferencial modulada (MDSC) demonstrou que o POSS é capaz de minimizar as flutuações de calor ao longo da microestrutura da resina epoxídica. A minimização das flutuações térmicas e a alteração dos tempos de relaxação demonstram que a adição do POSS é eficiente em termos de minimização de imperfeições na microestrutura da resina epoxídica. / The thermosetting resins are a class of polymers that due to the crosslinking reaction should present a single chain with infinite molecular weight; however, questions suggest that the formation of three-dimensional network is non-homogeneous. Today, due to advancements in nanotechnology, became possible a differentiated approach in the chemical modification of polymers such as epoxy resin. In this work, nanocomposites with different contents of the polyhedral oligomeric silsesquioxane (POSS) n-phenylaminopropyl in epoxy resin were prepared. It was substituted 1, 5 and 10 weight percent (wt%) of the crosslinking agent, triethylenetetramine (TETA), for POSS. This modification was performed in order to promote greater concentration of interconnections at the interfaces of the regions described as nodular imperfections or discontinuities that arise due to inhomogeneous cure of the resin. Through the morphology and the gel content analysis was observed good dispersion and improvements in the uniformity of three-dimensional network of the resin up till 5 wt% of the POSS and increase in the gel fraction of the nanocomposites compared with pure epoxy resin. X-ray diffraction (XRD) showed that the POSS promoted an increase in distance between chains of the resin. Dynamic-mechanical analysis (DMA) was performed in non-isothermal mode and a frequency sweep in the isothermal mode. By non-isothermal mode the results showed that the POSS shifted the Tg to higher temperatures and does not modify the crosslink density. The isothermal mode was used to determine the parameter of the Williams-Landel-Ferry (WLF) and Vogel-Fulcher-Tammann (VFT) equations. The distribution of the relaxation H(t) and retardation L(t) spectra was calculated through the storage (E') and loss (E'') modulus obtained by the DMA isothermal mode. The WLF and VFT parameters showed that the incorporation of POSS at the same time increased the Tg reduced the activation energy of segmental motion and made the epoxy resin structurally stronger. The reduction in the activation energy was associated with reduced intermolecular forces whereas the decrease in the structural fragility is associated with the fact that the POSS be able to interconnect the interfaces of the nodular regions. The H(t) and L(t) spectra showed that the nodules formed in the crosslinking process disappeared. The determination of the heat capacity (Cp) and excess entropy (Sex), analyzed by modulated differential scanning calorimetry (MDSC), showed that POSS is capable of minimizing fluctuations of heat along the microstructure of the epoxy resin. The reduction of thermal fluctuations and change in the relaxation times shows that the POSS addition is efficient to minimize imperfections in the microstructure of the epoxy resin.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-08-30Bitstream added on 2014-06-13T18:29:01Z : No. of bitstreams: 1 rangel_sa_me_ilha.pdf: 1557624 bytes, checksum: 38398c09b8ff17af075a211027a27833 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Polímeros epoxídicos são um dos mais importantes tipos de polímeros termorrígidos, extensivamente usados como adesivos e estruturas. Em reações epoxídicas são convertidos em um sistema termorrígido pela ação de agentes de cura. Tais reações químicas provocam uma mudança no estado físico do material, partindo de um líquido viscoso para um gel e se transformando em um material vitrificado. Os termorrígidos apresentam excelentes propriedades, tais como: alta tensão de ruptura e módulo de Young, fácil processamento, resistência térmica e química, e estabilidade dimensional. Entretanto, são quebradiços e possuem baixa resistência a propagação de trincas. Para superar estes inconvenientes, muitos tipos de compósitos de polímero com reforço foram desenvolvidos, em que as resinas epoxídicas são reforçadas com agentes modificadores, tais como enchimentos, oligômeros poliédricos de silsesquioxanos, dendrímeros, etc. Oligômeros poliédricos de silsesquioxanos (POSS), (RSiO1.5)n com n = 4, 6, 8, 10..., são nanoplataformas organo-funcionalizadas com 1 a 8 grupos reativos ou não reativos (R) ligados aos oito vértices possíveis do silsesquioxano cúbico. POSS octaédrico (n = 8) são os membros mais importantes desta família. No POSS, o núcleo cúbico de silicato é uma partícula rígida com 0,53 nm de diâmetro e um raio esférico de 1-3 nm, incluindo unidades orgânicas periféricas. Neste trabalho, um oligômero poliédrico de silsesquioxano contendo oito grupos epoxídicos por molécula (OG) foi incorporado ao sistema epoxídica DGEBA/DETA, como objetivo de avaliar a influência de um modificador reativo suas propriedades mecânicas e térmicas. Por meio de ensaios mecânicos foi observado um decréscimo de 30-50% na resistência à fratura (K1C)... / Epoxy resins are one of the most important kind of thermosetting polymers, extensively used for adhesives and structural applications. On cure, linear epoxy resins are undergoes in a thermoset system for the action of cure agents. Such chemical reactions cause a change into the physical state, from a viscous liquid to a gel and eventually to a vitrified material. They show various desirable properties such as high tensile strength and modulus, easy processing, good thermal and chemical resistance and dimensional stability, but they are brittle and have poor resistance to crack propagation. To overcome these drawbacks, many types of polymer-filler composites have been developed, in which the epoxy resins are reinforced with modifying agents, such as fillers, polyhedral oligosilsesquioxanes, dendrimers, etc. Polyhedral oligomeric silsesquioxanes (POSS), (RSiO1.5)n with n = 4, 6, 8, 10 ...., are organofunctional nanoplatforms with 1 to 8 reactive or nonreactive groups (R) connected to the eight possible vertexes of cubic silsesquioxanes. POSS Octahedral (n = 8) are the most important members of this family. In the POSS, the cubic core silica is a hard particle rigid with 0.53 nm diameter and a spherical radius of 1-3 nm including peripheral organic units. In this work, a polyhedral oligomeric silsesquioxanes containing eight epoxy groups per molecule (OG) was incorporated to an epoxy system of DGEBA/DETA thermosetting polymers in order to investigate the influence of a reactive modifier over the their mechanical and thermal properties. Through the mechanical tests an decrease of about 30-50% was observed in the fracture toughness (K1C) without or with a very soft decreasing in the module of Young (E)... (Complete abstract, click electronic address below)