Competitive sorption of water vapor and CO2 in photocrosslinked PVCA film for a capacitive‐type humidity sensor

The sorption behavior of water vapor and CO₂ gas in photocrosslinked poly(vinyl cinnamate) (PVCA) film was examined at 30°C under atmospheric pressure. Both the water sorption isotherm and the CO₂ sorption isotherm obtained with quartz crystal microbalance (QCM) method obeyed the simple Langmuir's equation. Water vapor/CO₂ mixed‐gas sorption isotherms were also obtained. Total amount of sorbed mixed gases was clearly influenced by the partial pressure of water vapor (p_w) and CO₂ gas (p_c) in the atmosphere. A modified Langmuir's equation based on a dual‐site model was employed for predicting the competitive adsorption isotherm, and the isotherm was clearly described by the equation. The theoretically estimated amount of adsorbed water at the constant p_w decreased slightly with increasing p_c. The effect of this phenomenon on the sensitivity of the capacitive‐type relative humidity sensor was examined. As expected, the electrical capacitance of the sensor at the constant relative humidity decreased because of the coexistence of CO₂ gas. However, the influence was quite small in the CO₂ concentration range in the ordinary environment. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 401–407, 2002     

Immobilization of glucose oxidase on nonwoven fabrics with bombyx mori silk fibroin gel

The enzyme glucose oxidase (GOD) was immobilized on the nonwoven fabrics, which have excellent properties in diffusivity of substrates, mechanical strength, and handling, with Bombyx mori silk fibroin gel. The nonwoven fabrics of silk fibroin, viscose rayon, poly-ethyleneterephthalate, 6-nylon, and polypropylene with activated surface by fluoline treatment were used. The stabilities of GOD to heat or pH changes were much improved by the immobilization as well as the case of the GOD immobilized in the silk fibroin membrane. Among nonwoven fabrics, silk fibroin was the most excellent support material for the immobilization of GOD although all nonwoven fabrics used here are able to be used as the support materials. The increase of the sensitivity was observed when the glucose sensor was made with the GOD immobilized on nonwoven silk fabrics as four times compared with the case of the GOD immobilized in the silk fibroin membrane.     

Novel vitamin E derivative with 4-substituted resorcinol moiety has both antioxidant and tyrosinase inhibitory properties

A novel vitamin E derivative, (6″-hydroxy-2″,5″,7″,8″-tetramethylchroman-2″-yl) methyl 3-(2′,4′-dihydroxyphenyl)propionate (TM4R), which has a chromanoxyl ring and 4-substituted resorcinol moieties, was synthesized; and its inhibitory effects on tyrosinase, antioxidant ability, and lightening effect of ultraviolet B (UVB)-induced hyperpigmentation were estimated. TM4R showed potent inhibitory activity on tyrosinase, which is the rate-limiting enzyme in melanogenesis. The scavenging activities of TM4R on 1,1-diphenyl-2-picrylhydrazyl and hydroxyl radicals were found to be nearly the same as those of α-tocopherol. Furthermore, an efficient lightening effect was observed following topical application of TM4R to UVB-stimulated hyperpigmented dorsal skin of brownish guinea pigs. These results suggest that TM4R may be a candidate for an efficient whitening agent, possibly by inhibiting tyrosinase activity and biological reactions caused by reactive oxygen species.     

Morphological evolution and mechanical property enhancement of natural rubber/polypropylene blend through compatibilization by nanoclay

Nanocomposites of natural rubber (NR)/polypropylene (PP) (80/20 wt %) blends filled with 5 phr pristine clay were prepared by melt‐mixing process. Effects of clay incorporation technique via conventional melt‐mixing (CV) and masterbatch mixing (MB) methods on nanostructure and properties of the blend nanocomposites were investigated. The XRD, SAXS, WAXD, and TEM results showed that the clays in the NR/PP blend nanocomposites were presented in different states of dispersion and were locally existed at the interface between NR and PP as well as dispersed in the NR matrix. The presence of clay caused unique morphological evolution such as fine fibrillar PP domains. The tensile strength was improved over the unfilled NR/PP blends by 53% and 224%, and the storage modulus at 25 °C was increased by 78% and 120% for the NR/PP/clay nanocomposites prepared by CV and MB methods, respectively. Significant improvement in both properties was particularly obtained from the MB method due to finer dispersion fibrillar PP phase in the NR matrix and stronger interfacial adhesion between NR and PP fibers, as suggested from DMA. The oil resistance of blend nanocomposites was also improved over that of the unfilled NR/PP blend, and this property was further progressed by the masterbatch mixing method. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44574.     

Evaluation of hydrogen absorption properties of Ti–0.2 mass% Pd alloy in fluoride solutions

The hydrogen absorption properties of Ti–0.2 mass% Pd (Ti–0.2Pd) alloy in 2.0% and 0.2% acidulated phosphate fluoride (APF) and neutral 2.0% NaF solutions (25 °C) has been evaluated by hydrogen thermal desorption analysis. During the early stage of immersion (120 h) in the 2.0% APF solution, the amount of absorbed hydrogen was lower than 500 mass ppm. A thermal desorption of hydrogen primary appearing with a peak at 500–600 °C and a broad desorption ranging from 100 to 400 °C were observed. In the 0.2% APF solution, the amount of absorbed hydrogen saturated at 100–200 mass ppm; the thermal desorption of hydrogen appeared with a single peak at 550 °C. In the 2.0% NaF solution, hydrogen absorption was negligible even after 1000 h of immersion, although corrosion pits were observed. The results of the present study suggest that the hydrogen absorption of Ti–0.2Pd alloy, as compared with commercial pure titanium, is suppressed in fluoride solutions.     

Evaluation of hydrogen absorption behaviour during acid etching for surface modification of commercial pure Ti, Ti-6Al-4V and Ni-Ti superelastic alloys

The hydrogen absorption behaviour during acid etching for the surface modification of commercial pure Ti, Ti-6Al-4V and Ni-Ti superelastic alloys has been investigated on the basis of the surface morphology, electrochemical behaviour and hydrogen thermal desorption analysis. To simulate the conventional acid etching for the improvement of the biocompatibility of Ti alloys, the specimens are immersed in 1 M HCl, 1 M H₂SO₄ or 0.5 M HCl + 0.5 M H₂SO₄ aqueous solution at 60 °C. Upon immersion, commercial pure Ti absorbs substantial amounts of hydrogen irrespective of the type of solution. In H₂SO₄ or HCl + H₂SO₄ solutions, the hydrogen absorption occurs for a short time (10 min). For Ti-6Al-4V alloy, no hydrogen absorption is observed in HCl solution, whereas hydrogen absorption occurs in other solutions. For Ni-Ti superelastic alloy, the amount of absorbed hydrogen is large, resulting in the pronounced degradation of the mechanical properties of the alloy even for an immersion time of 10 min, irrespective of the type of solution. The hydrogen absorption behaviour is not necessarily consistent with the morphologies of the surface subjected to corrosion and the shift of the corrosion potential. The hydrogen thermal desorption behaviour of commercial pure Ti and Ni-Ti superelastic alloy are sensitively changed by acid etching conditions. The present results suggest that the evaluation of hydrogen absorption is needed for each condition of acid etching, and that the conventional acid etching often leads to hydrogen embrittlement.     

Numerical Evaluation of Toughening by Crack-Face Grain Interlocking in Self-Reinforced Ceramics

Crack bridging associated with the pull-out process of interlocking grains in self-reinforced ceramic materials is studied through a micromechanical simulation. The pullout of a single inclined grain is modeled via the numerical solution of a general contact problem. The bridging-force versus crack-opening-distance curve indicates a nonlinear, springlike response for the pullout of interlocking grains. The sliding friction along the debonded interface, induced by highly localized contact stresses, dominates the total bridging force. The bridging force increases with grain inclination until eventual bridge failure. The pullout of misaligned grains mainly affects short-crack toughening, with a rising R -curve, whereas aligned grains contribute to long-crack toughening. The residual stresses of the thermal expansion anisotropy play a minor role in the pull-out process of grain interlocking and the resultant toughening. The proposed mechanism is operative in both single-phase and composite ceramics in which pullout of elongated grains/reinforcements occurs.     

Effect of crosslinking structure on sorption of CO2 in photocrosslinked PVCA film

The sorption behavior of CO₂ gas in photocrosslinked poly(vinyl cinnamate) film was examined under atmospheric pressure. The sorption isotherm was well described by the Langmuir equation, suggesting that sorption of CO₂ is mainly governed by adsorption in the microvoids. The amount of sorbed CO₂ was significantly affected by the degree of crosslinking. The CO₂ sorption was enhanced at a lower degree of crosslinking but was decreased at a higher degree of crosslinking. The unexpected increase in the amount of adsorbed CO₂ correlated with the increase in the number of microvoids that occurred as a result of the crosslinking reaction. However, further crosslinking led to a decrease in the mean size of the microvoids. The smaller microvoids, in comparison to CO₂ molecules, did not act as adsorption sites, so that the amount of sorbed CO₂ decreased. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1744–1750, 2000     

Incorporation of a well-defined polyether side-chain into segmented poly(ether-urethane urea) and examination for blood-compatibility

A new method of introducing a hydrophilic polyether side chain into segmented polyurethane using a polypropylene oxide macromer with 1,3-diol at one chain-end, which behaves as chain extender, is described. In this procedure, a molecular-designed side-chain is incorporated quantitatively and directly into polyurethane biomedical elastomer. The design is also of interest to biomaterials in artificial organs.