Advanced Materials Research Vol. 853

Abstract: Topical oral dosage form for anti-inflammation in the oral cavity provides convenience and patient compliance. Formulations of orabase gels composed of poloxamer 407, PVP, PVA, SCMC and/or white petrolatum (WP) and hydrocarbon gel (HG) were investigated for in vitro swelling and mucoadhesion for incorporation of melatonin. The highest detachment time of 18 h with an optimized swelling ratio of 1.3 was obtained from a gel with 55% of WP and HG in the presence of poloxamer 407 and PVP 90. In conclusion, an optimum balancing ratio between hydrocarbons and bioadhesive polymer parts is required to obtain mucoadhesive characteristics of the oral gel.

Abstract: Clay, rocks, concrete and other composite solids show evidence of a hierarchical structure. A fractal tree of nested viscoelastic boxes is proposed to describe the elastic after-effects in these composite solids. A generalized fractal transmission line approach is developed to relate the strain and stress responses. Power law for strain, under an applied stress step, is derived. The exponent in the power law is obtained as a well-defined function of the branching numbers and scaling parameters of the viscoelastic hierarchy. Then, a composite solid with both instantaneous (linear) elastic strain response and power law type (linear) elastic after-effect for an applied stress step, is considered. The stretched exponential stress relaxation to an applied strain step is derived as an approximation. For the same composite solid, the stretch parameter of the stretched exponential and the exponent of the power law result to be equal to each other.

Abstract: TiN-coated aluminum pigments were prepared by nanoparticle-bonding technology of high-energy ball milling. The effect of ball milling on the morphology and evolution of the composite powders was investigated via field-emission scanning electron microscopy, transmission electron microscopy, and particle size distribution analysis. Results show that the TiN nanoparticles bonded to the surface of aluminum microflakes under the action of a mechanical force but in the absence of any binder. A uniform nanoparticle coating formed on the surface of the flake aluminum microparticle. The optical reflectance of the TiN/Al composites was measured within 200 nm to 2500 nm wavelength. The reflectance gradually decreased as the milling time was prolonged.

Abstract: In this paper, the effects of strengthening epoxy matrices with nanopowders are discussed. Investigate the changes of reaction viscosities after adding different hardeners, nanoparticles and diluents to the polymer matrices. Analyze the applications to the automatic electronic packaging. The results show that different species in the curing reaction systems of epoxy will affect flow stabilities. Reaction viscositiesare affected primarily by the choice of hardeners. Nanoparticles will increase system viscosities and shorten matrix resin gel time. Adding diluents will help spread the powders and material flows in the systems, but is relatively not good for stability.

Abstract: Nanocomposite samples containing epoxy resin, glass fiber and 0~2 wt.% SiO₂ nanopowder are prepared. The effects of SiO₂ addition on the chemical resistance, glass transition temperature (Tg) and dynamic mechanical properties of the various samples are then observed. The chemical resistance of the nanocomposite specimens is compared with that of pure glass fiber/epoxy composite specimens when tested in acetone. The results show that the addition of 2 wt.% SiO₂ increases the value of storage modulus by 1646MPa compared to that of the sample containing no silica nanopowder. Following immersion in acetone, all the nanocomposite specimen storage modulus decreased, but the addition of SiO₂ reduced the decline, where the 2 wt. % samples decrease from 11.76% reduction to 0.84% and no significant change in the Tg compared to that of the sample with no silica nanopowder. Therefore, the experimental results indicate that 2 wt.% SiO₂ addition is beneficial in improving chemical resistance, glass transition temperature, and dynamic mechanical properties of epoxy resin / glass fiber nanocomposites.

Abstract: In this paper, epoxy, diluents, nanosilica powders and hardeners are mixed and cured form nanocomposites under different production conditions such as the amount of added nanopowders, diluents, etc. Through the use of an impact tester and a Shore durometer, the influences of the amount of added diluents and silica on mechanical properties are investigated. The results show that adding nanopowers has little effect on increasing the Shore D hardness. However, adding diluents will reduce the Shore D hardness of the composites. Without diluents, the composite added 1 wt.% of nanopowders has a maximum impact value of 6.63 KJ/m². Adding 3.2 wt.% of diluents, the nanocomposite has a maximum impact value of 5.50 KJ/m², also happens when the amount of added nanopowders is 1 wt.% of. Adding nanopowders more than 1 wt.% will reduce the impact strength. Nevertheless, adding nanopowders to 3 wt.%, the value is still higher than the composites without nanopowders.

Abstract: Nanocomposite samples containing epoxy resin, glass fiber and 0~2 wt.% SiO₂ nanopowder are prepared. The effects of SiO₂ addition on the water absorption rate, glass transition temperature (Tg) and dynamic mechanical properties of the various samples are then observed. The water absorption of the nanocomposite specimens is then compared with that of pure glass fiber/epoxy composite specimens when tested in water. The results show that the addition of 2 wt.% SiO₂ reduces the water absorption from 0.0704% to 0.0573%. The storage modulus with adding 2wt.% silica nanocomposite compared to the neat composite raises up 13.82%. Following the water absorption test, the mechanical properties of the samples are not obvious change. Therefore, the experimental results indicate that 2wt.% SiO₂ addition is beneficial to the water resistance and dynamic mechanical properties of epoxy resin / glass fiber nanocomposites.

Abstract: Epoxy resin nanocomposite samples containing 0~3wt.% reactive diluent and 0~3wt.% silica nanopowder are prepared. The preparation process is presented for solvent-free and greenmanufacturing. The storage modulus, loss modulus and glass transition temperature of the various samples are then evaluated via Dynamic Mechanical Analysis (DMA). For samples containing 0wt.% and 3wt.% reactive diluent, respectively, 3wt.% nanoSiO₂ addition is found to increase the storage modulus by 51.06 % and 22.22 %, respectively. In addition, it is found that the loss modulus is determined principally by the level of SiO₂ addition, whereas the glass transition temperature is determined mainly by the level of reactive diluent addition.

Abstract: We demonstrate the structural reorganization of microdomain arrays toward the perpendicular orientation of lamellar morphology in high-molecular-weight PS-b-PMMA films using a combinational approach by solvent-vapor and sequential thermal annealing processes. Solvent annealing with a PMMA-selective acetone vapor induced a cylindrical morphology. However, the sequential thermal annealing of block copolymer (BCP) films led to structural reorganization to an equilibrium lamellar morphology, where the lamellar microdomains were oriented to normal to the film surface. This technique suggests an efficient route for directing orientation and structural reorganization of microdomain arrays in the thin films of high-molecular-weight BCP self-assembly.