Characterisation of Fuel Cell Membranes as a Function of Drying by Means of Contact Angle Measurements

In another paper in this volume, it is demonstrated that the electrochemical interface in MEAs, and thus the polarization performance of the resulting fuel cells, can be improved by optimising the hot‐pressing procedure in the MEA preparation. In particular, the extent of drying of the membrane during MEA preparation was shown to be critical. In the present investigation, the effect of the drying process, and thus water content, on the hydrophilicity, wetting, and surface energies of some fuel cell membranes is examined. Wetting and surface energies are well known to influence the bonding behaviour of materials. Conclusions about how membrane drying and changes in water content influence membrane bonding and the relative importance of these surface effects are drawn.     

Synthesis and thermal properties of poly(styrene-co-ally alcohol)-graft-stearic acid copolymers as novel solid–solid PCMs for thermal energy storage

A series of poly(styrene-co-allyalcohol)-graft-stearic acid copolymers were synthesized as novel polymeric solid–solid phase change materials (SSPCMs). The graft copolymerization reactions between poly(styrene-co-allyalcohol) and stearoyl chloride were verified by Fourier transform infrared (FT-IR) and Proton Nuclear Magnetic Resonance (¹H NMR) spectroscopy techniques. The crystal morphology of the SSPCMs was investigated using polarized optical microscopy (POM) technique. Thermal energy storage properties of the synthesized SSPCMs were measured using differential scanning calorimetry (DSC) analysis. The POM results showed that the crystalline phase of the copolymers transformed to amorphous phase above their phase transition temperatures. Thermal energy storage properties of the synthesized SSPCMs were investigated by differential scanning calorimetry (DSC) and found that they had typical solid–solid phase transition temperatures in the range of 27–30 °C and high latent heat enthalpy between 34 and 74 J/g. Especially, the copolymer with the mole ratio of 1/1 (poly(styrene-co-allyalcohol)/stearoyl chloride) is the most attractive one due to the highest latent heat storage capacity among them. The results of DSC and FT-IR analysis indicated that the synthesized SSPCMs had good thermal reliability and chemical stability after 5000 thermal cycles. Thermogravimetric (TG) analysis results suggested that the synthesized SSPCMs had high thermal resistance. In addition, thermal conductivity measurements signified that the synthesized PCMs had higher thermal conductivity compared to that of poly(styrene-co-allyalcohol). The synthesized copolymers as novel SSPCMs have considerable potential for thermal energy storage applications such as solar space heating and cooling in buildings and greenhouses.     

The Investigation of Antifungal Activity and Durability of Natural Silk Fabrics Dyed with Madder and Gallnut

In this study, five silk fabrics were separately dyed with madder (Rubia tinctorium L.) and gallnut (Quercus infectoria Olivier) in different percentages and then tested for antifungal activity against Candida albicans DSMZ 1386. The one having highest antifungal activity was washed 5 times under same conditions and samples were taken after every wash. They retained nearly 99.98 % activity up to five launderings against Candida albicans. In addition, coloring compounds and their peak heights in dyed silk fabrics were detected by high performance liquid chromatography with diode array detection (HPLC-PDA). Color values of the dyed silk fabrics were measured by CIEL*a*b* spectrophotometer.     

Mitigating driver distraction with retrospective and concurrent feedback

OBJECTIVES: An experiment was conducted to assess the effects of retrospective and combined retrospective and concurrent feedback on driver performance and engagement in distracting activities. BACKGROUND: A previous study conducted by the authors showed that concurrent (or real time) feedback can help drivers better modulate their distracting activities. However, research also shows that concurrent feedback can pose additional distractions due to the limited time and resources available during driving. Retrospective feedback, which is presented at the end of a trip (i.e., post-drive), can include additional information on safety critical situations during a trip and help the driver learn safe driving habits. METHOD: A driving simulator study was conducted with 48 participants and 3 conditions: retrospective feedback, combined feedback (both retrospective and concurrent), and no feedback (baseline case). RESULTS: The feedback conditions (retrospective and combined) resulted in faster response to lead vehicle braking events as depicted by shorter accelerator release times. Moreover, combined feedback also resulted in longer glances to the road. CONCLUSIONS: The results suggest that both feedback types have potential to improve immediate driving performance and driver engagement in distractions. APPLICATION: Combined feedback holds the most promise for mitigating the effects of distraction from in-vehicle information systems.     

Unscented Kalman filter performance for closed-loop nonlinear state estimation: a simulation case study

In this paper, unscented Kalman filter (UKF) is used for state estimation of nonlinear system. The main advantage of UKF is that it does not need any linearization for calculating the state transition matrix like extended Kalman filter (EKF). This study includes the combination of the nonlinear estimation and the optimal control strategy. Simulation results for a proportional integral derivative and linear quadratic regulator controlled inverted pendulum are presented and compared with the EKF under the measurement and process noise. The results show that the performance of the UKF is better than the EKF in terms of robustness, computation time and speed of convergence.     

Preparation and textile application of poly(methyl methacrylate-co-methacrylic acid)/n-octadecane and n-eicosane microcapsules

In this study, a series of microencapsulated phase change materials with poly(methyl methacrylate-co-methacrylic acid) P(MMA-co-MAA) shell and n-octadecane or n-eicosane core were synthesized by emulsion polymerization method. The aim was to produce microencapsulated n-alkanes having functional groups on their outer surface, so that functional groups would help increasing physical interactions between microcapsules and fiber surface. Therefore, methyl methacrylate (MMA), ethylene glycoldimethacrylate (EGDM), and methacrylic acid (MAA) were copolymerized in oil phase of n-alkane. FT-IR results proved the successful synthesis of P(MMA-co-MAA) shell of microencapsulated n-alkanes. The DSC results indicated that the microencapsulated n-alkanes have considerable latent heat storage capacity in a range of 58–145 J/g. The average melting and freezing temperatures of the microencapsulated n-alkanes were measured as 27 and 26 °C for n-octadecane and 36 and 35 °C for n-eicosane, respectively. The microcapsules were of spherical and compact shape with particle sizes between 15 and 32 μm. The microcapsules on the cotton fabric applied by pad-dry-cure method were found highly durable and they showed sufficient stability upon several washings and rub fastness. Thermo-regulating properties of the fabrics were declared as a result of thermal history measurements.     

Synthesis and thermal properties of poly(n‐butyl acrylate)/n‐hexadecane microcapsules using different cross‐linkers and their application to textile fabrics

This study focused on the preparation, characterization, and determination of thermal properties of microencapsulated n‐hexadecane with poly(butyl acrylate) (PBA) to be used in textiles with heat storage property. Microcapsules were synthesized by emulsion polymerization method, and the particle size, particle size distribution, shape, and thermal storage/release properties of the synthesized microcapsules were analyzed using Fourier‐transform infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry techniques. Allyl methacrylate, ethylene glycol dimethacrylate, and glycidyl methacrylate were used as cross‐linkers to produce unimodal particle size distribution. MicroPBA microcapsules produced using allyl methacrylate cross‐linker were applied to 100% cotton and 50/50% cotton/polyester blend fabrics by pad‐cure method. The mean particle size of microcapsules ranges from 0.47 to 4.25 μm. Differential scanning calorimetry analysis indicated that hexadecane in the microcapsules melts at nearly 17°C and crystallizes at around 15°C. The contents of n‐hexadecane of different PBA microcapsules were in the range of 27.7–50.7%, and the melting enthalpies for these ratios were between 65.67 and 120.16 J/g, respectively. The particle size and thermal properties of microcapsules changed depending on the cross‐linker type. The cotton and 50/50% cotton/polyester blend fabrics stored 6.56 and 28.59 J/g thermal energy, respectively. The results indicated that PBA microcapsules have the potential to be used as a solid‐state thermal energy storage material in fabrics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fatty acid/poly(methyl methacrylate) (PMMA) blends as form-stable phase change materials for latent heat thermal energy storage

Fatty acids such as stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA) are promising phase change materials (PCMs) for latent heat thermal energy storage (LHTES) applications, but high cost is the most drawback which limits the utility area of them in thermal energy storage. The use of fatty acids as form-stable PCM will increase their feasibilities in practical LHTES applications due to reduced cost of the energy storage system. In this regard, a series of fatty acid/poly(methyl methacrylate) (PMMA) blends, SA/PMMA, PA/PMMA, MA/PMMA, and LA/PMMA were prepared as new kinds of form-stable PCMs by encapsulation of fatty acids into PMMA which acts as supporting material. The blends were prepared at different mass fractions of fatty acids (50, 60, 70, 80, and 90% w/w) to reach maximum encapsulation ratio. All blends were subjected to leakage test by heating the blends over the melting temperature of the PCM. The blends that do not allow leakage of melted PCM were identified as form-stable PCMs. The form-stable fatty acid/PMMA (80/20 wt.%) blends were characterized using optic microscopy (OM), viscosimetry, and Fourier transform infrared (FT-IR) spectroscopy methods, and the results showed that the PMMA was compatible with the fatty acids. In addition, thermal characteristics such as melting and freezing temperatures and latent heats of the form-stable PCMs were measured by using differential scanning calorimetry (DSC) technique and indicated that they had good thermal properties. On the basis of all results, it was concluded that form-stable fatty acid/PMMA blends had important potential for some practical LHTES applications such as under floor space heating of buildings and passive solar space heating of buildings by using wallboard, plasterboard or floor impregnated with a form-stable PCM due to their satisfying thermal properties, easily preparing in desired dimensions, direct usability without needing an add encapsulation and eliminating the thermal resistance caused by shell and thus reducing cost of LHTES system.     

Thermal energy storage properties of polyethylene glycol grafted styrenic copolymer as novel solid-solid phase change materials

Polymeric solid-solid phase change materials (S-SPCMs) are functional materials with phase transition-heat storing/releasing ability. With this respect, a series of polyethylene glycol (PEG) grafted styrenic copolymer were produced as novel S-SPCMs. PEGs with three different molecular weights were used for synthesis of isocyanate-terminated polymers (ITPs). To achieve cross-linking S-SPCMs, the ITPs were grafted with styrene-co-ally alcohol) (PSAA) at three different PSAA:PEG mole ratios. The produced polymers were characterized using Fourier transform infrared (FT-IR), proton nuclear magnetic resonance (¹H NMR), and X-ray diffraction (XRD) technique. The crystalline-amorphous phase transitions of the polymers were examined using polarized optical microscopy (POM). The FT-IR, NMR, and XRD results confirmed the expected chemical structures and crystallization performances of the polymers. Thermal energy storage (TES) properties of the S-SPCMs were determined by differential scanning calorimetry (DSC). The DSC results revealed that the polymers with grafting ratio of PSAA:PEG(1:1) had phase transition enthalpies between about 74 and 142 J/g and phase transition temperatures between about 26°C and 57°C. Thermogravimetric analysis (TGA) measurements demonstrated that the S-SPCMs were resistant to thermal decomposition until about 300°C. Thermal conductivities of the produced S-SPCMs were measured in a range of about 0.18 to 0.19 W/mK. Furthermore, TES properties of the S-SPCMs were slightly changed as their chemical structures were remained after 5000 thermal cycles. By overall evaluation of the findings, it can be foreseen that particularly PSAA-g-PEG(1:1) polymers can be considered as promising S-SPCMs for some TES practices such as air conditioning of buildings, thermoregulation of food packages, automobile components, electronic devices, and solar photovoltaic panels.     

A general methodology for machine tool accuracy enhancement by error compensation

A general methodology for increasing the accuracy of machine tools by compensating for the inherent systematic errors is described. This methodology in