The incorporation of nanoscale fillers into a polymer can lead to a considerable improvement of mechanical properties, i.e. stiffness and toughness of a material can be enhanced simultaneously by the insertion of nanofillers. Thereby, the crucial difference between conventional microscale fillers and nanofillers is the high specific surface of the latter. In order that this surface can interact with the matrix material a good dispersion, i.e. a good separation and a homogeneous distribution of the nanoparticles into the polymer, is required. In the present study ultrasonic waves generated by an ultrasonic horn were used to disperse titanium dioxide nanoparticles into epoxy resin. The process parameters, e.g. the ultrasonic amplitude, the dispersion time and the material's volume, were varied systematically with the aim of achieving an optimum dispersion process. A dispersion model for bead mills was adapted to the ultrasonic process and compared to a second dispersion model in order to find an adequate mathematical expression to correlate the ultrasonic process parameters to the particle sizes in the material and to allow predictions for further experiments.

By the insertion of nanoparticles into a polymer matrix a considerable improvement of mechanical properties can be achieved. Therefore, a homogeneous distribution of fillers within the matrix is required. In the present paper the dispersion of TiO(2)-nanoparticles in a DGEBA (diglycidyl ether of bisphenol A) epoxy resin by means of an ultrasonic horn was studied. The systematic examination of process parameters of a previous study was completed in order to determine the optimum processing window leading to a good dispersion result without degrading the molecular structure of the epoxy resin. Therefore, particle sizes were examined using a dynamic light scattering device, and the effect of the ultrasonic treatment on the resin was surveyed by FT-IR spectroscopy (Fourier transform infrared spectroscopy). Furthermore, the mechanical performance of the nanocomposites was examined for various contents of TiO(2)-nanoparticles to show that the materials prepared by ultrasonic dispersion show an improved property's profile. In order to understand the reinforcing mechanisms of nanoparticles in the polymer matrix providing improved mechanical properties, scanning electron microscope (SEM) pictures of the fracture surfaces of the samples were carried out, which revealed that nanocomposites show a significantly rougher surface than the neat epoxy resin. This indicates a change in the fracture mechanisms.

Biopolymers are gaining increasing interest because of decline of mineral oil reserves, increasing waste problem, and increasing consciousness of society for environmental problems. However, competitiveness of biopolymers compared with conventional plastics is still limited due to partly insufficient properties and high prices. This study investigates the influence of blending of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with poly(butylene adipate-co-terephthalate) (PBAT) as well as the influence of addition of functionalized montmorillonite (OMMT) to the blends on morphology and thermal behavior. Dispersion state and morphology of the nanocomposites are studied by X-ray diffraction as well as scanning electron microscopy. Thermal stability is studied by thermogravimetric analysis and crystallization behavior is studied by differential scanning calorimetry and polarized optical microscopy. With respect to the morphology for the blends it can be seen that the immiscible biopolymers PHBV and PBAT are distributed in interlocking zones. There is a good dispersion and homogeneous distribution of OMMT within the biopolymer blends. The addition of 50% or more PBAT to PHBV as well as the insertion of OMMT enhances thermal stability of PHBV. In the blends, the addition of PBAT retards crystallization of PHBV. The OMMT acts as nucleating agent leading in total to more but less perfect crystals in the blends, and the crystallization slows further due to constraint in the movement of polymer chains. These results contribute to the understanding of the structure-properties relationship of bionanocomposite materials for packaging applications. POLYM. COMPOS., 36:2051-2058, 2015

Composite materials formed by a LAS matrix reinforced with second phases are promising materials in many applications where better mechanical properties than those corresponding to conventional low thermal expansion coefficient materials are required. In this study we will show the capability of the design of a LAS-alumina submicron composite. The main scope of this work is to test the sinterability of the composites and to design a composition for a very low thermal expansion submicron composite. For this purpose, Taimei alumina (TM-DAR) powders and an ad hoc synthesized ␤-eucryptite phase were used to fabricate the composite. XRD phase compositions and microstructures are discussed together with data from dilatometries in a wide temperature range. The results obtained show the possibility of designing a submicron composite with a very low thermal expansion coefficient and improved mechanical properties that can be used in oxidizing conditions.

Due to the short‐running of mineral oil and the increasing waste problem, biopolymers become more and more important. However, they still suffer from disadvantages, and in many cases, their properties are still insufficient to replace mineral oil based plastics. In this study, the biobased and biodegradable polymer poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) is reinforced by different clay types and their effect on the properties profile is investigated. Natural as well as organomodified montmorillonite and bentonite are dispersed by melt mixing within the PHBV matrix. Thermal stability, crystallization behavior, and dynamic mechanical properties as well as the materials morphology is analyzed. Dispersion state of the nanoclay is found to be crucial for the improvement of the material performance and well dispersed organomodified clays reveal to simultaneously improve different properties of PHBV matrix. POLYM. COMPOS., 34:1033–1040, 2013. © 2013 Society of Plastics Engineers

Increasing generation and inadequate disposal of waste progressively compromise our environment. Solutions are proposed by the development of biodegradable polymers, that is, for short‐term applications like packaging. The present study focuses on the design and characterization of biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) nanocomposites reinforced by different types of nanoclays. The addition of natural and modified montmorillonite and bentonite to PBAT by melt mixing enhances slightly the thermal stability and increases the crystallization temperature, independently of the fillers' dispersion state. By contrast, storage modulus in dynamic mechanical analysis is increased when adding nanoclay, and improvement is higher for well‐dispersed organomodified fillers. Dispersion states and morphology of the nanocomposites are studied by X‐ray diffraction as well as scanning and transmission electron microscopy. PBAT‐based composites with modified bentonite reveal to show the best performance at room temperature (which is the temperature of interest for potential packaging applications) in comparison with the other investigated nanocomposites.POLYM. COMPOS., 33:2022–2028, 2012. © 2012 Society of Plastics Engineers

Nanocomposites gained more and more importance in the last few years because of their improved performance over the neat polymer matrix, that is, toughness and stiffness can be enhanced simultaneously by the addition of nanoparticles. However, the dispersion of these particles in the matrix remains a big challenge. In this study, two types of TiO 2 nanoparticles were dispersed in two different epoxy resins by means of ultrasound. The particle size development in dependence on the dispersion time was investigated by dynamic light scattering for the different material systems. Furthermore, the influence of the viscosity on the sonication process' efficiency was analyzed. The resulting nanocomposites were tested for fracture and Charpy toughness. SEM images revealed that the improved fracture toughness properties are correlated to a rougher fracture surface, whose formation dissipates more energy.

A capacidade de controlar a dispersão de nanotubos de carbono (CNT) em polímeros é considerada ponto chave para a maioria das aplicações de compósitos de nanotubo/polímero. A dispersão de nanotubos de carbono em água com diferentes surfactantes, assim como sua incorporação em resinas fenólicas, foi investigada. Ultrasonicação de suspenções líquidas foi usada para preparar dispersões estáveis. A fim de se avaliar o melhor surfactante a ser usado, espalhamento de luz e espectroscopia UV-Visível foram empregados. A estrutura de CNT reforçada de resina fenólica foi analisada em função da concentração e tipo de surfactante, potência e tempo de sonicação. A influência da dispersão pelo uso das propriedades de transição de temperatura vítrea também foi avaliada, sendo obtida por análise mecânica dinâmica e energia de impacto.The ability to control the carbon nanotube (CNT) dispersion in polymers is considered the key to most applications of nanotube/polymer composites. The carbon nanotube dispersion into water with different surfactants, as well as its incorporation into phenolic resins, was investigated. Ultrasonication of liquid suspensions was used to prepare stable dispersions. In order to evaluate the best surfactant to be used, light scattering and UV-Visible spectroscopy were employed. The structure of CNT reinforced of phenolic resin was analyzed in function of the concentration and type of surfactant, sonication power and time. It was also evaluated the influence in the dispersion by using the glass temperature transition properties being obtained by dynamic mechanical analyses and impact energy. Keywords: carbon nanotubes, polymeric composites, phenolic resin IntroductionPolymer composites based on carbon nanotubes (CNTs) have attracted tremendous attention during these last years due to the impressive mechanical properties of CNTs, including high modulus value (around 1TPa), strength of 50-200 GPa, failure strain of up to 15% and electrical conductivity ranging from semiconducting to metallic, depending on their structure. [1][2][3][4][5] The interaction between functional groups of the compatibilizer and carboxyl or amine groups of multi wall carbon nanotubes (MWCNTs) stabilized the morphology and improved the interfacial interaction between MWCNTs and the thermoset matrix. 6,7 In general, the nanoscale dispersion of MWCNTs in polymeric matrix is achieved by strong hydrogen bonding between hydroxyl groups of the MWCNTs and polymer groups. Therefore, despite the extremely high strength of individual CNT shells, the weak shear interactions between adjacent shells and tubes lead to significant reductions in the effective strength of multi-walled carbon nanotubes. [8][9][10][11][12] This is responsible for the carbon nanotube bundles down to only a few GPa. [8][9][10][11][12] Nowadays, phenolic resins are indeed irreplaceable materials for selective high-technology applications, offering high reliability under severe conditions. Because of its excellent ablative properties, structural integrity, thermal stabili...