Effect of surface structure of porous silica microballoons on dynamic mechanical properties of amine cured epoxy resin composites

Dynamic mechanical properties were studied for epoxy resin filled with porous silica microballoons with varying surface area, pore radius, pore volume and adsorbed water. The glass transition temperature (T_g) of the composites is 12–14°C lower than the T_g of the unfilled epoxy resin. This T_g depression is attributed to the preferential adsorption of curing agents on the porous silica microballoons. Tg of the composite increases with increase in the adsorbed water on fillers. The storage modulus has a distinct correlation with the Hg-surface area of silica microballoons, which corresponds to the sum of the surface area of pores with radii larger than about 4 nm. Tan δ_c tan δ_m decreases with increasing Hg-surface area.     

An electrochemical oxygen separator using an ion-exchange membrane as the electrolyte

An electrochemical oxygen separator based on oxygen reduction at an air cathode and oxygen evolution at an anode has been developed. The device features use of an ion-exchange membrane (Nafion 117) as the sole electrolyte and an air cathode mainly made of carbon.The anode was formed by chemically plating platinum (3.7 mgcm^–2) on one side of the Nafion 117 membrane. The air cathode was bonded to the other side of the membrane by spraying a slurry of graphitized furnace black loaded with platinum, followed by hot-pressing. The addition of a Nafion solution and a PTFE dispersion to the slurry was essential. The ultimate loading of platinum for the cathode was 0.2 mg cm^–2. An electrochemical oxygen separator with a working area of 100 cm² was constructed. When the separator was used as an oxygen concentrator it could be operated at 200 mA cm^–2 and produced 70.9 cm³ min^–1 of oxygen with a purity of 98.4%. When the separator was used as a circulation-type oxygen removal system it reduced the oxygen concentration of a 10-dm³ chamber to less than 0.02% within 70min. When the separator was used as a flow-through-type oxygen remover, air with an oxygen concentration of 0.02% was produced at 100 cm³ min^–1.     

Epoxy Networks Modified by a New Class of Oligomeric Silsesquioxanes Bearing Multiple Intramolecular Rings Formed through Si?O?C Bonds

Summary: A new class of silsesquioxane (SSO), containing species with two to nine Si atoms bearing multiple intramolecular rings formed through Si? O? C bonds, was synthesized as a glassy powder. It was characterized by UV‐MALDI‐TOF MS, ²⁹Si NMR and FT IR. Solutions containing different amounts of SSO in the diglycidyl ether of bisphenol A (DGEBA), were homopolymerized in the presence of (4‐dimethylamino)pyridine (DMAP) as initiator, leading to SSO‐modified epoxy networks. SSO species were covalently bonded to the epoxy network without any evidence of phase separation. The SSO addition provoked an increase in the elastic modulus in the glassy state explained by an increase in the cohesive energy density. The SSO addition gave also place to an increase in the intensity of tan δ and a decrease in both the glass transition temperature and the elastic modulus in the rubbery state. This was explained by a decrease in crosslink density associated with the flexibility of SSO structures. DMAP was much more effective than other usual initiators (like benzyldimethylamine, BDMA), in increasing the crosslink density of the resulting epoxy network. This led to high values of the glass transition temperature and the elastic modulus in the rubbery state.

Schematic representation of the chemical structure of the most significant species containing three Si atoms, present in the silsesquioxane.     

High‐performance polymer‐stabilized blue‐phase LCD with low driving voltage

We have developed a polymer‐stabilized blue‐phase LCD in which the diffraction wavelength of blue‐phase liquid crystal is in the ultraviolet region and which is driven at a low voltage of V₁₀₀ = 27 V. Prototypes of 3.4‐in polymer‐stabilized blue‐phase LCDs were made, which include a highly reliable crystalline oxide semiconductor. We succeeded in fabricating not a test cell but a display having a contrast ratio higher than 1000 : 1 for the first time in the world.     

Tribochemical Reactions and Lubricating Effects of Fluorinated Methanes for Al2O3 Ceramic

It has been found that CF₃CH₂F (HFC-134a) gas is an effective lubricant for several ceramics because of the formation of fluorine-containing tribochemical products. To understand the influence of the molecular structure of fluorine-containing gases on the lubricating characteristics, the lubricating effects and tribochemical reactions of some fluorinated methanes for Al₂O₃ ceramic were studied. X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectroscopy (TOF-SIMS) were used to identify the chemical structure of tribochemical products. It was found that the friction and wear of Al₂O₃ ceramic were dependent on the molecular structure of the reacting fluorocarbon gases. The lowest friction was obtained in CH₂F₂. CHF₃ showed the best anti-wear effect. The results of surface analyses indicate that greater amounts of tribochemical products are produced when Al₂O₃ rubs in CH₂F₂ than in CF₄ and CHF₃ gases. C–C/C–H/carbon and AlF₃, which are mainly formed on the sliding surface in CH₂F₂, are responsible for the low friction. The mechanism of tribochemical reactions of the different environmental molecules on the nascent surface of Al₂O₃ was also discussed.     

Toxicity of anionic detergents determined by Saccharomyces cerevisiae microarray analysis

Sodium n-dodecyl benzene sulfonate (LAS) and sodium dodecyl sulfate (SDS) are popular anionic detergents (surfactants) that are used worldwide and the toxicities of these chemicals have been characterized. We applied these chemicals in a DNA microarray bioassay and determined that the microarray data reflects previous findings and also provides some new information about anionic detergent toxicity. The mRNA expression profiles suggest that LAS and SDS cause damage to membranes and alterations in carbon metabolism, and induce the oxidative stress response. We also found that LAS and SDS induce the pleiotropic drug-resistance network, and that LAS and SDS may be pumped out of yeast cells by this network. Hierarchical clustering of the expression profiles showed that LAS and SDS cause similar features of toxicity and that the toxicity is similar to that of capsaicin but different from that of cadmium and mercury.     

Package images modulate flavor perception for orange juice

Most food packages contain images as well as textual information. While the influence of textual information on flavor evaluation has been well studied, the influence of images remains unexplored. Thus, this study investigated how the valence and congruency of images on juice packages influence flavor evaluations. There were 85 participants divided between four experimental conditions: (1) pleasant/congruent, with pleasant orange pictures; (2) unpleasant/congruent, with unpleasant orange pictures; (3) pleasant/incongruent, with pictures of pleasant non-food objects; and (4) unpleasant/incongruent, with pictures of unpleasant non-food objects. In each condition, pictures were attached to cups filled with juice. The participants rated the palatability, goodness of aroma, sweetness, bitterness, sourness, richness, freshness, and artificiality of 6 samples of the same juice. Juices presented with pleasant images were rated as more palatable and fresh. Juices presented with congruent images were rated with better aromas. This data shows that images on juice packages influence flavor evaluation.     

Reinforcement Mechanism of Carbon Black (CB) in Natural Rubber Vulcanizates: Relationship Between CB Aggregate and Network Structure and Viscoelastic Properties

Carbon black (CB) aggregates in CB-filled natural rubber (NR) vulcanizate were joined together and formed CB aggregates in the CB region less than 20?phr. It was found that the viscoelastic behavior was related to the hydrodynamic interaction between CB aggregate and NR matrix. In the CB loading region more than 40?phr, CB aggregates formed CB network structure in it. Using the parallel mechanical model of the two phases of a rubber matrix and an immobilized CB/NR interfacial layer excluding a CB phase, it was possible to quantitatively explain the relationship between the viscoelastic behavior of CB network structure.     

SYNERGISTIC EXTRACTION OF EUROPIUM(III) WITH BENZOIC ACID AND THENOYLTRIFLUOROACETONE

ABSTRACT

The solvent extraction of europium(III) into solutions of thenoyltrifluoroacetone and benzoic acid in cyclohexane, carbon tetrachloride, benzene, chloroform, pentachloroethane, and tetrachloroethane has been measured at 25°C. It has been found that the extracted species involve two types of adducts, EuA₃· HB and EuA₃· 2HB where A denotes the TTA anion and HB the benzoic acid monomer. The magnitude of the adduct formation constants in different solvents has been correlated with the dimerization constants of benzoic acid in the solvents.     

Response of osteoblast-like MG63 cells to TiO2 layer prepared by micro-arc oxidation and electric polarization

Micro-arc oxidation (MAO) is one of the useful surface modifications of titanium implants to improve bioactivity. Also, electric polarization treatment enhances bioactivity of calcium phosphate. The aim of this study was to evaluate the effect of the combination of two surface modifications, micro-arc oxidation (MAO) with electric polarization, on the behavior of osteoblast-like osteosarcoma MG63 cells. MAO-treated materials had a surface geometry that was favored by MG63 cells as determined using scanning electron microscopy and X-ray diffraction; additionally, electric polarization induced surface electric fields, which were measured using thermally stimulated depolarization currents. The results of assays to study cell–material interactions suggest that these two approaches could regulate cell attachment, spreading, proliferation, and differentiation without the addition of other reagents. This new surface modification processes produce materials with a good surface geometry, generate surface electric fields and enhance the osteopromotive ability of osteoblasts.