Manas Chanda

Photocatalytic degradation of organic dyes in aqueous solution with TiO2 nanoparticles immobilized on foamed polyethylene sheet

Degussa TiO2 nanoparticles have been immobilized on a foamed polyethylene by thermal bonding to produce a stable catalyst sheet containing 0.7 mg TiO2 cm(-2) and retaining 40-50% of active surface area of the particles. On such a catalyst sheet, exposed to radiation of a 125 W mercury vapour lamp, decomposition of about 0.3 mg of methylene blue (MB) is obtained per cm(2) in 1 h at ambient temperature from an aqueous solution of 200 ppm MB. The rate data fit well to classical Langmuir-Hinshelwood (L-H) rate form. This rate form also results from mechanisms based on the assumption of hydroxyl radical formation on the irradiated catalyst and a reaction between the hydroxyl radical and the organic dye molecule, either or none of them being adsorbed on the catalyst surface. An activation energy of 14.5 kcal mol(-1) is obtained for the photocatalytic decomposition of methylene blue following the L-H rate laws.

Use of maleic anhydride–grafted polyethylene as compatibilizer for HDPE–tapioca starch blends: Effects on mechanical properties

Tapioca starch in both glycerol-plasticized and in unplasticized states was blended with high-density polyethylene (HDPE) using HDPE-g-maleic anhydride as the compatibilizer. The impact and tensile properties of the blends were measured according to ASTM methods. The results reveal that blends containing plasticized starch have better mechanical properties than those containing unplasticized starch. High values of elongation at break at par with those of virgin HDPE could be obtained for blends, even with high loading of plasticized starch. Morphological studies by SEM microscopy of impact-fractured specimens of such blends revealed a ductile fracture, unlike blends with unplasticized starch at such high loadings, which showed brittle fracture, even with the addition of compatibilizer. In general, blends of HDPE and plasticized starch with added compatibilizer show better mechanical properties than similar blends containing unplasticized starch

A Fickian diffusion model for permeable fibre polymer composites

A brief description of the Fickian diffusion behaviour in polymer composites, con taining impermeable fibres (glass and graphite) is presented. The applicability of such a model to composites based on a permeable fibre phase (jute) is verified, both under the influence of varied internal (fibre volume fraction) and external (ambient temperature) factors. Very good correlations are found between the experimental data and a modified Fickian diffusion plot. The significance of a resin impregnated fibre volume fraction in such a composite is highlighted.

Gel-coated ion-exchange resin : A new kinetic model

Abstract Regenerable ‘gel-coated’ cationic resins with fast sorption kinetics and high sorption capacity have application potential for removal of trace metal ions even in large-scale operations. Poly(acrylic acid) has been gel-coated on high-surface area silica (pre-coated with ethylene–vinyl acetate copolymer providing a thin barrier layer) and insolubilized by crosslinking with a low-molecular-weight diepoxide (epoxy equivalent 180 g) in the presence of benzyl dimethylamine catalyst at 70°C. In experiments performed for Ca 2+ sorption from dilute aqueous solutions of Ca(NO 3 ) 2 , the gel-coated acrylic resin is found to have nearly 40% higher sorption capacity than the bead-form commercial methacrylic resin Amberlite IRC-50 and also several times higher rate of sorption. The sorption on the gel-coated sorbent under vigorous agitation has the characteristics of particle diffusion control with homogeneous (gel) diffusion in resin phase. A new mathematical model is proposed for such sorption on gel-coated ion-exchange resin in finite bath and solved by applying operator-theoretic methods. The analytical solution so obtained shows good agreement with experimental sorption kinetics at relatively low levels (

Monte Carlo simulation of network formation based on structural fragments in epoxy-anhydride systems

A method combining the Monte Carlo technique and the simple fragment approach has been developed for simulating network formation in amine-catalysed epoxy-anhydride systems. The method affords a detailed insight into the nature and composition of the network, showing the distribution of various fragments. It has been used to characterize the network formation in the reaction of the diglycidyl ester of isophthalic acid with hexahydrophthalic anhydride, catalysed by benzyldimethylamine. Pre-gel properties like number and weight distributions and average molecular weights have been calculated as a function of epoxy conversion, leading to a prediction of the gel-point conversion. Analysis of the simulated network further yields other characteristic properties such as concentration of crosslink points, distribution and concentration of elastically active chains, average molecular weight between crosslinks, sol content and mass fraction of pendent chains. A comparison has been made of the properties obtained through simulation with those predicted by the fragment approach alone, which, however, gives only average properties. The Monte Carlo simulation results clearly show that loops and other cyclic structures occur in the gel. This may account for the differences observed between the results of the simulation and the fragment model in the post-gel phase.

Plastics Fabrication and Recycling

Fabrication Processes Types of Processes Tooling for Plastics Processing Compression Molding Transfer Molding Injection Molding of Thermoplastics Injection Molding of Thermosetting Resins Extrusion Blow Molding Calendering Spinning of Fibers Thermoforming Casting Processes Reinforcing Processes Reaction Injection Molding Structural Reaction Injection Molding Resin Transfer Molding Foaming Processes Rubber Compounding and Processing Technology Miscellaneous Processing Techniques Decoration of Plastics Recycling of Polymers Introduction Outline of Recycling Methods Recycling of Poly(Ethylene Terephthalate) Recycling of Polyurethanes Recycling of Poly(Vinyl Chloride) Recycling of Cured Epoxies Recycling of Mixed Plastics Waste Post-Consumer Polyethylene Films Recycling of Ground Rubber Tires Recycling of Car Batteries Plastic Recycling Equipment and Machinery Appendices Index of Trade Names and Suppliers of Foaming Agents Formulations of Polyurethane Foams Formulations of Selected PVC Compounds Formulations of Selected Rubber Compounds Commercial Polymer Blends and Alloys Index References appear at the end of each chapter.

Oxidation of Aqueous Sulphur Dioxide Catalysed by Poly‐4‐vinylpyridine–Cu(II) Complex. Part 2: Combined Homogeneous and Heterogeneous Phase Oxidation

Aqueous phase oxidation of sulphur dioxide at low concentrations catalysed by a PVP-Cu complex in the solid phase and dissolved Cu(II) in the liquid phase is studied in a rotating catalyst basket reactor (RCBR). The equilibrium adsorption of Cu(II) and S(VI) on PVP particles is found to be of the Langmuir-type. The diffusional effects of S(IV) species in PVP-Cu resin are found to be insignificant whereas that of product S(VI) are found to be significant. The intraparticle diffusivity of S(VI) is obtained from independent tracer experiments. In the oxidation reaction HSO3- is the reactive species. Both the S(IV) species in the solution, namely SO2(aq) and HSO3- get adsorbed onto the active PVP-Cu sites of the catalyst, but only HSO3- undergoes oxidation. A kinetic mechanism is proposed based on this feature which shows that SO2(aq) has a deactivating effect on the catalyst. A rate model is developed for the three-phase reaction system incorporating these factors along with the effect of concentration of H2SO4 on the solubility of SO2 in the dilute aqueous solutions of Cu(II). Transient oxidation experiments are conducted at different conditions of concentration of SO2 and O-2 in the gas phase and catalyst concentration, and the rate parameters are estimated from the data. The observed and calculated profiles are in very good agreement. This confirms the deactivating effect of nonreactive SO2(aq) on the heterogeneous catalysis.

Oxidation of aqueous sulfur dioxide catalyzed by poly-4-vinylpyridine–Cu(II) complex. Part 1: Homogeneous phase oxidation

The oxidation of aqueous sulfur dioxide in the presence of polymer-supported copper(II) catalyst is also accompanied by homogeneous oxidation of aqueous sulfur dioxide catalyzed by leached copper(II) ions. Aqueous phase oxidation of sulfur dioxide of low concentrations by oxygen in the presence of dissolved copper(II) has therefore been studied. The solubility of SO2 in aqueous solutions is not affected by the concentration of copper(II) in the solution. In the oxidation reaction, only HSO3- is the reactive S(IV) species. Based on this observation a rate model which also incorporates the effect of sulfuric acid on the solubility of SO2 is developed. The rate model includes a power-law type term for the rate of homogeneous phase reaction obtained from a proposed free-radical chain mechanism for the oxidation. Experiments are conducted at various levels of concentrations of SO2 and O-2 in the gas phase and Cu(II) in the liquid phase. The observed orders are one in each of O-2, Cu(II) and HSO3-. This suggests a first-order termination of the free radicals of bisulfite ions.

Direct Synthesis of Nano-size Polymers by Microemulsion Polymerization

Microemulsions can be used as reaction media for free-radical polymerization of monomers. Polymerization, initiated in various ways (thermal, photochemical, or γ-irradiation), occurs in monomer reservoirs encapsulated in the nano-size space of microemulsion structures, producing thermodynamically stable nano-size latexes ( 106) polymers. Millions of tons of polymer microlatexes are thus produced annually, some notable examples being butadiene–styrene copolymers, poly(vinyl acetate), poly(vinyl chloride), acrylate ester copolymers, polyacrylamide and derivatives. These latexes are used in diverse fields including coatings, adhesives, binders, paints, flocculants, and rheological modifiers, while many novel applications, such as in separation technology, catalysis, and drug delivery, are being explored.

Corrosion and Radiation

The importance of stability of a material or a component under service conditions cannot be over-emphasized. Lack of stability considerations has often resulted in a premature failure of costly machines and parts. Service conditions involving the effects of temperature, irradiation, and chemical environment produce alterations in materials, which may be internal affecting the structure and thus leading to property changes, or on the surface causing material losses.