Effect of PES on the morphology and properties of proton conducting blends with sulfonated poly(ether ether ketone)

Development of alternate materials to Nafion, based on ionically conducting polymers and their blends is important for the wider applications of proton exchange membrane fuel cells. In this work, blends of sulfonated poly(ether ether ketone) (SPEEK) with poly(ether sulfone) (PES) are investigated. SPEEK with various ion exchange capacity (IEC) was prepared and blended with PES, which is nonionic and hydrophobic in nature. A comparative study of the water uptake, proton conductivity, and thermo‐mechanical characteristics of SPEEK and the blend membranes as a function of the IEC is presented. Addition of PES decreases the water uptake and conductivity of SPEEK. Chemical and thermal stability and mechanical properties of the membrane improve with the addition of PES. The effect of water content on the thermo‐mechanical properties of membranes was also studied. The morphology of blend membranes was studied using SEM to understand the microstructure and miscibility of the components. On the basis of the results, a plausible microstructure of the blends is presented, and is shown to be useful in understanding the variation of different properties with blending. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Lignin Degradation by Flavodon flavus (Klotzsch.) Ryv. and Schizophyllum commune Fr. on Mangifera indica and Syzygium cumini Woods

Abstract

The lignin degradation by Flavodon flavus (Klotzsch) Ryv. and Schizophyllum commune Fr. on Mangifera indica and Syzygium cumini wood, changes in the chemical composition of the degraded wood, and production of extra-cellular lignocellulolytic enzymes were analyzed. White rot fungi F. flavus and S. commune selectively degraded the lignin of S. cumini rather than the holocellulose component, whereas simultaneous degradation of lignin occurred in the case of M. indica. After 90 days of pretreatment with F. flavus, total weight loss was 29% and loss in lignin content was 25.7% in M. indica wood. However, 8% loss of holocellulose was caused by S. commune in S. cumini wood. Extracellular enzymes from F. flavus such as ligninase and cellulase showed higher activity in degradation of M. indica wood than in S. cumini wood. Weight loss and changes in chemical composition of M. indica and S. cumini woods showed good correlation with enzyme activity in lignocellulose degradation. Woods of S. cumini showed resistance to the white rot fungi could be due to the presence of polyphenols.     

Development of a Dual-Modal Presentation of Texts for Small Screens

Baddeley's (1986) Baddeley, A. D. 1986. Working memory, New York: Oxford University Press.  [Google Scholar] working memory model suggests that imagery spatial information and verbal information can be concurrently held in different subsystems. This research proposed a method to present textual information with network relationships in a “graphics + voice” format, especially for small screens. It was hypothesized that this dual-modal presentation would result in superior comprehension performance and higher acceptance than pure textual display. An experiment was carried out to test this hypothesis with analytical problems from the Graduate Record Examination. Thirty individuals participated in this experiment. The results indicate that users' performance and acceptance were improved significantly by using the “graphic + voice” presentation. The article concludes with a discussion of the implications and limitations of the findings for future research in multimodal interface design.     

Swelling and diffusion characteristics of polar and nonpolar polymers in asphalt

The swelling and diffusion characteristics of a polar polymer [ethylene vinyl acetate (EVA)] and a nonpolar polymer [low-density polyethylene (LDPE)] were studied with swelling experiments of the polymers in asphalt at different temperatures. The study showed that the diffusion mechanisms for LDPE and EVA were different and temperature-dependent. In the case of LDPE, the observed diffusion was anomalous at both swelling temperatures (70 and 90°C). LDPE at 90°C showed sigmoidal solvent-uptake behavior during the initial period of swelling and a sorption overshoot in a later period. EVA showed Fickian transport at 60°C and anomalous diffusion at a higher swelling temperature (70°C) with sigmoidal uptake behavior. An analysis of the diffusion coefficients and the Fourier transform infrared results showed that the diffusing molecules were different in the case of LDPE and EVA, and there were possible polymer–asphalt interactions. Differential scanning calorimetry and swelling studies showed that penetrant-induced crystallization affected the diffusion process in the case of LDPE. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Disease appearance and evolution against a background of climate change and reduced resources

Global health continues to face increasing challenges owing to a variety of reasons that include the almost constant changes in disease appearance and evolution. Most, but not all, of these changes affect low-income countries and are influenced by climate change. Tracking the recent and anticipated changes in the demographics and global distribution of these changes is essential for evolving effective new methods for dealing with the problems. The recent recognition by the United Nations of the importance of non-communicable diseases is a major positive step. For the sake of this paper, the following diseases were chosen: dengue and malaria, to highlight the role of climate change on vector-borne diseases. Drug-resistant tuberculosis illustrates the role of globalization and reduced resources on disease evolution. The continuing rise in cardiovascular mortality and morbidity, particularly in resource-poor countries is largely attributed to lack of preventive and therapeutic measures against such conditions as hypertension, diabetes, atherosclerosis and congenital heart disease as well as neglected diseases, of which Chagas and rheumatic heart disease will be discussed further.     

Morphology control and ionic crosslinking of pectin domains to enhance the toughness of solvent cast PVA/pectin blends

Blending water soluble synthetic polymers, such as polyvinyl alcohol (PVA), with natural polymers, such as pectin, has many advantages. However, due to the brittle nature of pectin, the mechanical properties become inferior in the blends. In this work, two strategies to enhance the toughness and tensile strength of solvent cast PVA/pectin blends are presented. This study shows that the tensile strength and toughness of PVA/pectin 80/20 blends can be enhanced by decreasing the solvent evaporation rate. The phase separation proceeds through 'nucleation and growth' and spinodal decomposition, respectively, at lower and higher rates of solvent evaporation. The equilibrium phase morphology has spherical domains of pectin dispersed in the PVA matrix. The size of the pectin domains and the separation between them are controlled by the solvent evaporation rate. At higher rates of solvent evaporation, pectin domains are larger and farther apart from each other and vice versa. Ionically crosslinking the pectin domains with calcium, further enhances the tensile strength and toughness of the blends compared to that of pure PVA. When the pectin domains are small, the failure happens at larger strains through 'cavitation' and 'shear yielding' and when pectin domains are large, the failure happens at smaller strains and the failure mechanism shifts to 'multiple crazing'.     

Milling and separation of the multi-component printed circuit board materials and the analysis of elutriation based on a single particle model

Electronic waste, in the form of printed circuit boards (PCBs) or printed wiring boards (PWBs), represents a significant and growing fraction of the waste generated in many communities. It is necessary to identify schemes to manage and dispose this waste in an environmentally safe manner. The present work, examines the use of mechanical means to separate the metallic and non-metallic components present in PCBs. The unique characteristics of PCB construction pose challenges to the mechanical means of separation. In view of these unique characteristics of PCBs, an empirical approach is suggested to evaluate the effectiveness of the mechanical separation process. Two milling operations were used to obtain the feed for the separation using elutriation. Compositions of different size fractions from the milling operations are presented. Experimental data from the separation process is presented and the extent of use of mechanical means that results in optimum separation is identified. The separation efficiency is analyzed in terms of composition, particle size and operating condition of the elutriation flow rate. A probabilistic analysis based on single particle settling velocity shows that separation results with uniform particle size fraction can be described effectively. However, the probabilistic analysis captures only the qualitative features with mixed particle sizes and components.     

Novel polymer electrolyte membranes based on semi‐interpenetrating blends of poly(vinyl alcohol) and sulfonated poly(ether ether ketone)

In this work, the properties of novel ionic polymer blends of crosslinked and sulfonated poly(vinyl alcohol) (PVA) and sulfonated poly(ether ether ketone) (SPEEK) are investigated. Crosslinking and sulfonation of PVA were carried out using sulfosuccinic acid (SSA) in the presence of dispersed SPEEK to obtain semi‐interpenetrating network blends. PVA–SSA/SPEEK blend membranes of different compositions were studied for their ion‐exchange capacity, proton conductivity, water uptake, and thermal and mechanical properties. The hydrated blend membranes show good proton conductivities in the range of 10^?3 to 10^?2 S/cm. When compared with pure component membranes, the PVA–SSA/SPEEK blend membranes also exhibit improvement in tensile strength, tensile modulus, and delay in the onset of thermal and chemical degradation. Semi‐interpenetrating nature of the blends is established from morphology and dynamic mechanical analysis. Morphology of the membranes was studied using scanning electron microscopy after selective chemical treatment. The dynamic mechanical properties of the membranes are examined to understand the miscibility characteristics of the blends. The relative proportions of PVA and SPEEK and the degree of crosslinking of PVA–SSA are important factors in determining the optimum properties for the blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013