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This work investigated the extraction efficacy of phenolic acids on the potato and its byproducts. Also, the compositions of bioactive compounds and antioxidants were evaluated in various parts of the potato, such as the tuber, microtuber, peel, and flesh. The chemical constituents were quantified by HPLC analysis, and the highest levels of phenolics (88.99 mg/L) were obtained in acetone extracts from a micropropagated potato. The micropropagated potato demonstrated that notable phenolic compounds were mainly a bound form of phenolic acids including caffeic acid and vanillic acid. The micropropagated extracts using acetone showed the higher radical scavenging activity, 94.3% and 95.5% at 5 mg/mL in 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS·+), respectively. In addition, the same extracts showed the highest (85.61%) β-carotene bleaching inhibition activity. A positive relationship existed between DPPH and either ABTS·+ (r = 0.58, p

Three different polypropylene resins were selected to develop microporous membranes through melt spinning, annealing and stretching. The effects of take-up speed, cooling rate, stretching, and annealing temperature on the crystalline structure and orientation of the membrane were investigated using field emission scanning electron microscopy. An annealing process was employed to generate and enlarge the pores and lamellar structure, and improved the crystallinity of hollow fiber precursors, before the stretching process. The annealed hollow fiber precursor was stretched by cold, hot, and cold/hot complex stretching. We observed that porous structure on the outer and inner surfaces of the stretched precursor fibers were produced by cold and hot complex stretching.

Proton-conducting composite membranes were prepared from sulfonated poly(arylene ether sulfone) (SPAES) and silica-phosphate sol-gel by using a solution casting method. The silica and phosphate precursors of tetraethylorthosilicate (TEOS) and triethyl phosphate (TEP), and the sol-gel network formation of silica-phosphate, were confirmed using Fourier transform infrared (FTIR) spectroscopy. Increases in water affinity by incorporating silica-phosphate were observed in all composite membranes, which also resulted in higher ion-exchange capacity than with pure SPAES. The water desorption behavior of the SPAES composite membranes was determined by the weight loss at 80 °C using thermogravimetric analysis (TGA). The SPAES/7S3P (7 and 3 indicate the added molar ratio of silica and phosphate, respectively) composite membrane showed the strongest water retention capacity. As the temperature increased in fully hydrated conditions, all membranes exhibited increasing proton conductivity due to enhanced proton mobility. The proton conductivity at low humidity depended on the water retention capacity, indicating that the incorporation of silica-phosphate was effective in enhancing the proton conductivity through the hopping transfer. The best performance was obtained in the SPAES/7S3P composite membrane, showing a conductivity of 29.6 mS/cm at 120 °C with 40% relative humidity, which is twice to that of Nafion 112 (14.6 mS/cm).

An in situ sol-gel method was used to synthesize organic-inorganic composite membranes based on poly(arylene ether sulfone) (SPAES), phosphotungstic acid (PWA), and sulfonated silica (silica-SO3H). The PWA particles were functionalized with an organic silane compound to enhance proton conductivity. This study compares the performance of polymer electrolyte membrane fuel cells with different preparation methods for the membrane and composite of PWA-silica-SO3H particles. The optimum composition of PWA-silica-SO3H is determined on the basis of the mechanical properties, the behavior of water in the membrane, and the level of proton conductivity. The mechanical properties of the sol-gel composite membranes were improved with the introduction of PWA-silica-SO3H particles. The sol-gel composite membrane has higher levels of proton conductivity than the in situ composite membrane and pure SPAES membrane. An increase in the silica content of the PWA-silica sol-gel particles increases the proton conductivity because the inorganic component and the incorporation of PWA lead to a high concentration of hydroxyl groups. These properties make composite membranes potential candidates for direct methanol fuel cell applications. Open image in new window

Sulfonated poly(arylene ether sulfone) (SPAES)/sulfonated montmorillonite (SMMT) hybrid membranes were fabricated to evaluate their potential for use as direct methanol fuel cells (DMFCs). To minimize the loss of proton conductivity while reducing methanol permeability, an ion exchange method was used to prepare the SMMT including a sulfonic acid group. The SPAES/NMMT(-Na+) and SPAES/SMMT(-SO3H) hybrid membranes were prepared using a solution casting and evaporation method, and the NMMT/SMMT content in the composite membranes was controlled at 0.5–2.0 wt% based on the SPAES. The performances of the hybrid membranes for the DMFCs in terms of their mechanical and thermal properties, water uptake, water retention, methanol permeability, and proton conductivity were investigated. The mechanical and thermal properties of the SPAES membranes were improved with introduction of the NMMT and SMMT. Methanol permeability reduction was also obtained when the SMMT content and the sulfonation degree increased. The SPAES/SMMT composite membrane showed increased proton conductivity compared with the non-modified MMT composite membrane under the 100% relative humidity condition. As the modified MMT content increased, the proton conductivity increased and the methanol permeability decreased due to the monovalent ions located between the MMT layers. The ratio of methanol permeability to proton conductivity for the SPEAS/SMMT (2.0 wt%) composite membrane was higher than that of Nafion® 1135. This property makes hybrid membranes potential candidates for DMFC applications. Open image in new window

Sulfonated poly(styrene-b-ethylene/butylene-b-styrene)(S-SEBS)/clay composite membranes incorporating various types of clay were prepared to reduce the methanol permeability in a direct methanol fuel cell(DMFC). The dispersion of clay into the polymer matrix was confirmed by TEM. The water uptake and state were measured by DSC to understand the effect of the incorporation of clay types on the membrane hydrophilicity. These results showed a strong relationship between the proton conductivity and hydrophilicity of the clay. The thermal stability of the composite membrane was examined and the water evaporation rate at 100 °C was varied by the total amount of absorbed water. The highest proton conductivity and the lowest methanol permeability were obtained with the S-SEBS-Na+ membrane; these properties were affected by the hydrophilicity, interlayer spacing and dispersibility of clay.

The microstructures and mechanical properties of a high-Si (1.5 wt.%) steel produced by a novel process of quenching and partitioning (Q & P) were compared with those obtained using traditional heat treatments (i.e. austempering, intercritical annealing for dual phase, quench and tempering). Plate steel was included for exploration of the Q & P process in applications requiring strength and toughness (such as an API line pipe), where retained austenite may contribute to the overall toughness via the TRIP phenomenon at a crack top. The Q & P process is based on the partial transformation of austenite to martensite, followed by partitioning of carbon from martensite into austenite, which leads to an untypical microstructure. Retained austenite amounts up to 6 vol.% with a carbon content of up to 0.88 wt.% were achieved in 0.1% carbon steel using Q & P. Superior impact toughness at higher yield strength levels was found after Q & P compared to other traditional heat treatments with equivalent partitioning, austempering or tempering conditions.

In the present study, crosslinked poly(vinyl alcohol) (PVA) membranes were prepared at different temperatures using poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA) (PVA:PSSA_MA = 1:9). The hybrid membranes were prepared by varying the TEOS content between 5 and 30 wt%. The PSSA_MA was used both as a crosslinking agent and the hydrophilic group donor (-SO3H and/or -COOH). The proton conductivity increased with up to 20 wt% TEOS, but decreased above this level, although the water content decreased with increasing TEOS content. This result suggests that the silica doped into the membrane improved the formation of proton-conduction pathways due to the absorption of molecular water. The PVA/PSSA_MA/Silica containing TEOS 20% showed both high proton conductivity (0.026 S/cm at 90°C) and low methanol permeability (5.55×10-7 cm2/s).

Crosslinked poly(vinyl alcohol) (PVA) membranes were prepared at various crosslinking temperatures using poly(acrylic acid-co-maleic acid) (PAM) containing different PAM contents. The thermal properties of these PVA/PAM membranes prepared at various reaction temperatures were characterized using differential scanning calorimetry (DSC). The proton conductivity and methanol permeability of PVA/PAM membranes were then investigated as PAM content was varied from 3 to 13 wt%. It was found that the proton and methanol transport were dependent on PAM content in their function both as crosslinking agent and as donor of hydrophilic -COOH groups. Both these properties decreased monotonously with increasing PAM concentration. The proton conductivities of these PVA/PAM membranes were in the range from 10−3 to 10−2S/cm and the methanol permeabilities from 10−7 to 10−6cm2/sec. In addition, the effect of operating temperature up to 80 °C on ion conductivity was examined for three selected membranes: 7, 9 and 11 wt% PAM membranes. Ion conductivity increased with increasing operating temperature and showed and S/cm at 80 °C, respectively. The effects of crosslinking and ionomer group concentration were also examined in terms of water content, ion exchange capacity (IEC), and fixed ion concentration. In addition, the number of water molecules per ionomer site was calculated using both water contents and IEC values. With overall consideration for all the properties measured in this study, 7∼9 wt% PAM membrane prepared at 140 °C exhibited the best performance. These characteristics of PVA/PAM membranes are desirable in applications related to the direct methanol fuel cell (DMFC).

Poly(vinyl alcohol) (PVA) membranes crosslinked with poly(acrylic acid-co-maleic acid) (PAM) were prepared to investigate the effect of aging on their morphology by swelling them for up to 7 days. PAM was used both as a crosslinking agent and as a donor of the hydrophilic -COOH group. A 30 wt% weight loss of the dry membrane was observed in the swelling test after 6 days. The surface of the membrane was dramatically changed after the swelling test. The surface roughness of the PVA/PAM membrane was increased, as determined by atomic force microscopy (AFM). The swelling loosened the polymer structure, due to the release of the unreacted polymer and the decomposition of the ester bond, thereby resulting in an increase in the free volume capable of containing water molecules. The water molecules present in the form of free water were determined by differential scanning calorimetry (DSC). The fraction of free water increased with increasing swelling time. The swelling of the membrane may provide space for the transport of protons and increase the mobility of the protonic charge carriers. The proton conductivity of the membranes measured atT=30 and 50 °C was in the range of 10−3 to 10−2 S/cm, and slightly increased with increasing swelling time and temperature.

The long-term stability of sulfonic acid-containing polyimides has been investigated. The hydrolytic degradation of homopolyimide and the block copolyimide comprising 27 mol% of 2,2′-bis(trifluoromethyl)benzidine and 9 mol% ofm-phenylenediamine (BTFMB27mP10[7/(3+1)]), was quantified through viscosity measurements and FT-IR spectroscopic analyses. The viscosity decrease with respect to time and the degradation rate were similar. The degrees of degradation with respect to time under ambient conditions and at elevated temperature in water were monitored by FT-IR spectroscopy. A new absorption peak was observed at 1786 cm−1, which we corresponds to the presence of anhydride end groups formed by hydrolytic scission of the imide rings.

In this work, we prepared hydrogels for wound dressing from a mixture of poly(vinyl alcohol) (PVA) and alginate using the60Co γ-ray irradiation technique. We examined the physical properties of these hydrogels, including gelation, water absorptivity, and gel strength, to evaluate the applicability of these hydrogels for wound dressings. The biocompatibility of these hydrogels was also evaluated in vitro, in cultures of mouse fibroblasts, and in vivo, by subcutaneous implantation studies in rats. The gel content and strength increased upon increasing the radiation dose and upon decreasing the concentration of alginate. The degree of swelling was inversely proportional to the gel content and strength. The degree of cytotoxicity of the γ-ray-treated hydrogels was ca. 60% compared to the (−) control (serum) after 1 day of incubation. When the incubations were prolonged up to 2 days, the toxicity of all the samples decreased remarkably and reached that of the control. Subcutaneous implantation studies in rats indicated that foreign body reactions occurring around the implanted hydrogels were moderate and became minimal upon increasing the implantation time.

Several copolyimides have been synthesized with different combinations of comonomers in order to study the relationship between conductivity and water insolubility.m-Phenylenediamine (m-PDA), an angled comonomer, was introduced into the polymer backbone to increase water absorption, and resulted in higher proton conductivity. 2,2-bis(trifluoromethyl)benzidine (TFMB) was used as the comonomer to promote water insolubility. There is a good correlation between the water uptake and conductivity of the polyimides. The copolyimides that had high water uptake also generated high proton conductivity. Those polyimides had good mechanical properties. The copolyimides that have 27 mol% of TFMB and 9 mol% ofm-PDA have reasonable conductivities and are insoluble in water at 90 °C, even though they have lower conductivities than those of the homopolymer.

Blend membrane consisting of poly(vinyl alcohol)(PVA) and chitosan was prepared from solvent casting technique for effective separation of ethanol-water mixture by pervaporation. Selectivity toward water and the flux through the blend membrane, crosslinked with glutaraldehyde at the concention of 4×10-6 mol/g, were∼450 and 0.47 kg/m2.hr, respectively.