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Editor’s Choice : Structurally Functionalized Polyurethane Foam for Elimination of Lead Ions from Drinking Water
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Abstract: Polyurethane foams functionalized with Sulfonic acid groups have been found to be strong cation exchangers. This novel property of the foam was used to exchange lead (Pb2+) ions from aqueous solutions. Polyurethane foam synthesis is based on addition polymerization of the highly reactive isocyanate (-NCO) groups of an isocyanate with the hydroxyl (–OH) groups of a polyol to form the urethane species. Toluene-2,4-2,6- diisocyanate was reacted with Polypropylene glycol 1200 in 2:1 molar ratio to form a linear pre-polymer. The linear pre-polymer was further polymerized using a chain extender, N, N-bis (2-hydorxyethyl)-2-aminoethane-sulfonic acid (BES). BES also acts as a functional group to exchange Pb2+ ions. A set of experiments were designed to study various process parameters. The functionalized polyurethane foam was characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, scanning electron microscopy, and energy dispersive x-ray spectroscopy. The Pb2+ ion exchange capacity was determined using an Inductively Coupled Plasma Mass Spectrometer. The maximum Pb2+ ion exchange capacity of the foam was found to be 47 parts per billion per gram (ppb/g) from a 100 parts per billion (ppb) Pb2+ solution over a period of 60 minutes. A multistage batch filtration process increased the Pb2+ ion removal to 50-54 ppb/3g of foam over a period of 90 minutes. Keywords: Adsorption, Functionalized, Ion exchange, Polyurethane foams, Sulfonic.Download Full Article |
Editor’s Choice : Study on Flexural Strength and Flexural Failure Modes of Carbon Fiber/Epoxy Resin Composites
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Abstract: The flexural failure modes and flexural strength of unidirectional carbon fiber/epoxy (CF/epoxy) composites was theoretically analyzed and calculated. The hypothesis that the maximal flexural strength of unidirectional CF/epoxy composites occurred in outer sheet layer was brought forward. Load-displacement curve of unidirectional CF/epoxy composites also demonstrates that it is correct, which is consistent with the assume. Unidirectional CF/epoxy composites were fabricated with winding and compression molding, and three different kinds of fiber packing modes were proposed and the effects of these modes on flexural prosperities of composites had also been analyzed respectively. Three failure modes, namely fracture of fiber, fracture of epoxy resin and interfacial delamination between fiber and matrix, were analyzed by scanning electron microscopy (SEM). The load-displacement curve of unidirectional CF/epoxy composites indicates the plastic deformation is increased with increasing phenolic resin. Keywords: Bending strength, carbon fiber, packing modes, failure mode, composite.Download Full Article |
Editor's Choice : Optimization of Process Parameters for Generation of Nanocellular Polymer Foams
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Abstract: High melt strength polypropylene nanocomposites, PPNC/Cloisite 20A (clay) with exfoliated and intercalated morphologies were prepared and subsequently foamed in a batch setup under different foaming conditions. The foaming parameters were varied to relate the foam cell structure to these parameters and determine the efficiency of clay in producing fine cell foams. A Box Benkhen design approach was used initially to determine the effect of processing parameters on foam cell morphology and also to perform optimization studies. The optimization process helped in identifying the range of operating conditions needed to minimize foam cell sizes. Saturation pressure and temperature and foaming time and temperature are the four processing variables used in these studies. Nanocellular foam cells were effectively generated for the first time in Polypropylene nanocomposites. Keywords: Nanocellular, DOE, optimization, batch foaming.Download Full Article |
Editor's Choice : Organomodified Silicone Elastomer (OMSE) for Next Generation Personal Care Products
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Abstract: Personal care (PC) products containing commercial silicone elastomer (SE) blends offer superior sensory, due to their silky and non-greasy characteristics. These products contain functional organic actives; namely sunscreens, antibacterial agents and dyes. The functional performance of the PC products is determined by the extent of deposition of the actives on the skin or hair. However, this performance is limited due to incompatibility of organic actives with the silicone elastomer (SE) blend. This review described recent development of organomodified silicone elastomers (OMSE) for enhanced compatibility and superior deposition of actives on the skin or hair. OMSEs contain covalently linked functional actives to the cross-polymeric silicone backbone. OMSE were synthesized by reacting alkenyl functional derivatives of avobenzone, benzylidene malonate, curcumin or hydroxyanthraquinone, suitable crosslinker, solubilizing (e.g. CnH2n i.e. alkyl) / emulsifying agents (e.g. polyether) with the poly(dimethyl)-co-(methylhydrogen)siloxane copolymer in the presence of platinum catalyst. OMSE showed superior functional performance due to uniform molecular distribution of sunscreen / dye molecules on the substrate surface. Covalently attached sunscreen / dye molecules on the cross-polymeric silicone backbone would show enhanced safety profile due to negligible possibility of penetration through skin. Keywords: Organomodified polymer, silicone elastomers, skin / hair photodamage, hair color photodegradation, sunscreens, hair colorants, antibacterial polymers, active deposition.Download Full Article |
