Diffusion Foundations Vol. 23

Abstract: This chapter is devoted to organic-inorganic composite ion exchange resins and membranes. We ascertain interrelation between composition, morphology and porous structure of the materials on the one hand and ion transport through them on the other hand. The composites for different practical application (fuel cells, ion exchange columns, electrodialysis) are in a focus of attention. Porosity of a polymer constituent of the composite was determined with a method of standard contact porosimetry, which gives information about pores in a very wide diapason (from 2 nm to 200 μm). In this context, pore formation in ion exchange polymers during swelling is considered. A number of parameters, which are obtained from porosimetric measurements, can be used for interpretation of ion transport regularities, particularly evolution of electrical conductivity. Embedded non-aggregated nanoparticles, their aggregates and agglomerates affect differently porosity of the polymer constituent: they are able to block, stretch and squeeze pores, As a result, the composites demonstrates different rate of ion transport depending on amount and size of the inorganic particles. The approach to purposeful formation of one or other types of particles has been proposed.

Abstract: Gas separations through organic membranes have been investigated from last several years and presently it has been accepted for commercial applications. This chapter will focus on membrane based gas separation mechanism as well as its application. This chapter will cover ‘‘diffusivity controlled’’ and ‘‘solubility controlled’’ mechanism and choice of suitable polymers for different gas phase applications like acidic gas, C3+ hydrocarbon, nitrogen, water vapor and helium. Diffusivity controlled mechanism performs on free volume elements of the glassy polymers via hindrance of chain packing by functional groups and restricted by the permselectivity. Other mechanism performs on the basis of molecular structure with affinity towards the target molecule and follows enhanced solution-diffusion rout. Commercially available organic membrane materials for Carbon dioxide (CO₂) removal are discussed along with process design. Membranes based separation process for heavy hydrocarbon recovery, nitrogen separation, helium separation and dehydration are less developed. This article will help us to focus on the future direction of those applications based on membrane technology. Keywords: Membrane, C3+ hydrocarbon, Diffusivity controlled, Solubility controlled, Selectivity, Permeability. ^*Corresponding author: E-mail address: c.bhatta@gmail.com (Chiranjib Bhattacharjee), Tel.: +91-9836402118.

Abstract: In recent years, membrane separation technology has emerged as efficient and promising separation process from laboratory scale applications to wide range of technical industrial applications. The development of composite asymmetric membrane is a major breakthrough in membrane research field, as this membrane offers significantly high selectivity without affecting the mechanical durability of the membranes. In this chapter, structural characteristics and different fabrication techniques of composite membranes are reviewed. Moreover the mass transfer mechanism through the composite asymmetric membrane is described in details following solution-diffusion theory, Knudsen diffusion, and series resistance model. Composite membranes are preferred over others because of the high flux and enhanced selectivity without disturbing the mechanical stability of the membranes. These membranes are now widely employed in the applications of reverse osmosis (RO), nanofiltration (NF), pervaporation, gas separation, hydrocarbon fractionations, etc. As composite asymmetric membranes are “tailor-made” in nature, membrane characteristics can be tuned accordingly depending on their end use. Therefore plentiful research opportunities still exist to elevate their performance ability in terms of stability, selectivity and fouling resistance, which will in turn augment its application domain.

Abstract: Nanoparticles (NPs) are microscopic objects with at least one dimension less than 100 nm. These were first discovered by Michael Faraday in 1857 when he prepared gold nanoparticles and observed that nanostructured gold produced red color. This distinct feature of nanoparticles could be due to very small size. NPs are very small compared to the wavelengths of light, hence absorb light in the blue-green portion of the spectrum (~450 nm) and reflect the red light (~700 nm) thus yield a rich red color. NPs also possess very high surface to mass ratio that could be utilized in several application areas wherein a very high surface area is required. Nanoparticles witnessed tremendous growth in research and application areas especially in medicine in twentieth century after discovery of carbon nanotubes in 1991. Nanoparticles have been explored in medicine as targeted delivery carriers to deliver macromolecules such as proteins, enzymes, to the target organ up to cellular levels. Of late, these carriers have been employed to treat several tumors owing to its capacity to deliver chemotherapeutic agents to the tumor cells only thus improving efficacy and minimizing side effects of anticancer agents.

Abstract: The area of sorption and diffusion behaviour of wood/plastic composites has gained considerable attention during the last decade owing to the variety of applications it offers. When it comes to polymers filled with wood particles there are essentially two major limiting factors that controls the final products end user applications; 1) diffusion and 2) sorption/solvent uptake of (especially moisture) the product, since these two processes lead to property degradation in the composite materials. The properties and end use application of a given product can be predicted thorough the knowledge of the parameters like diffusion, sorption and permeation coefficients. Transport (sorption, diffusion & permeation) properties of wood plastic composites (WPC’s) are now a day’s one of the most intensively researched areas owing to its significance in materials science. Liquid transport through plastics is one of the most extensively researched fields in materials science. Present chapter provides a brief insight into the transport (mainly moisture/water) properties of wood/plastic composites. Keywords: Wood particles, wood plastic composites, diffusion coefficient

Abstract: This chapter presents the preparation and characterization of some unique properties of nanocomposites by dispersing graphite flakes in commercial unsaturated polyester (UPE) matrix. The composite was prepared by a novel method with the use of solvent swelling technique. Three different specimens of UPE/graphite nanocomposites were fabricated with addition of 1, 2 and 3 wt% of graphite flakes. Except mechanical, viscoelastic and thermo gravimetric properties, transport properties like electrical conductivity, thermal conductivity and water transport properties were studied for the first time. Graphite flakes propose enhanced properties to the composites suggesting homogeneous distribution of the nanofiller in the matrix and strong interaction with the matrix. 2wt% nanofiller loading showed superior essential characteristics and after that the properties reduced may be due to the nucleating tendency of the nanofiller particles. The XRD pattern showed the compatibility of the graphite flakes by introducing a peak around 26.55⁰ in the nanocomposites. SEM Properties are also in agreement with the compatibility. Nanocomposite with 2wt% graphite also showed remarkable enhancement in transport, mechanical, viscoelastic and thermo gravimetric properties. So by introduction of a small quantity of graphite endow the new class of multiphase nanocomposites with inimitable structure and tremendous application.

Abstract: Carbon nanotubes (CNTs) are made out of carbon atoms connected in hexagonal shapes, with every carbon molecule covalently attached to three other carbon particles. The properties of nanotubes have made scientists and organizations think about utilizing them in many fields. For instance, since carbon nanotubes have the most noteworthy quality to-weight proportion of any known material. Nanocomposites of adjusted multi walled carbon nanotubes (MWCNTs) installed in a polymer matrix yield a one of a kind mix of warm and electrical properties and mechanical quality. The composites combine the vast pseudo capacitance of the directing polymers with the quick charging/releasing two-fold film impedance and incredible machine-driven possessions of the carbon nanotubes. The electrochemically co-stored composites are the most homogeneous and demonstrate an unordinary communication between the polymer and nanotubes, offering ascend to a reinforced electron delocalisation and conjugation along the polymer chains

Abstract: The availability of sustainable and environmentally friendly energy sources is one of the biggest challenges faced by scientists and engineering communities. First of all, the fossil fuels used to meet existing energy demands cause the depletion of resources, the increase of greenhouse gas emissions, and eventually destruction of nature. Polymers have many industrial application areas due to the ease of processing, the reasonable price and the ability to modify with the desired features. Biopolymers have become a focus of attention in terms of the polymer sector because biomass can be separated into harmless products such as CO₂ and H₂O in the natural environment and can have sustainable resources. The studies on biomass and hydrogen fuel cells are more advantageous than other alternative and clean energy sources because they have the continuous energy supply, compact design, and wide application areas without being dependent on nature. In practice, the polymer electrolyte membrane fuel cells are pinched among the other fuel cells. For this purpose, in this chapter diffusion, transport and water absorption properties of eco-friendly polymer composites generally used are discussed.