Susy Varughese

Recycled Polyolefin-Based Plastic Wastes for Sound Absorption

Recycling of high-volume polyolefin-based packaging wastes in India is challenging, as they have low recycle value, high levels of contamination, and lack of direct processing methods. This work discusses a two-stage mechanical processing method for recycling the polyolefin-based plastic wastes that are not conventionally recycled. With the objective of improving specific properties like sound absorption and noise reduction, inhomogeneities were introduced in the recycled product. This was achieved by mixing polyolefin-based packaging wastes with other waste materials such as plastic-coated aluminium foils, expanded polystyrene, and coir pith in varying quantities. More than 30 times volume reduction was achieved by a two-stage compression molding process. The sound absorption properties of the recycled materials are found to be comparable to expanded polystyrene and glass wool when small quantities (2–3 wt%) of materials like expanded polystyrene waste and coir pith were added. Impact strength of the recycled material decreased with increasing amounts of secondary additives like metal foils. Flexural strength of the recycled material was found to be maximum at about 30 wt% of metal foils. The end product could find applications in the construction industry due to the sound-absorption properties and the mechanical strength.

Coalescence Dynamics of PEDOT:PSS Droplets Impacting at Offset on Substrates for Inkjet Printing.

UNLABELLED The dynamics of coalescence and consequent spreading of conducting polymer droplets on a solid substrate impacting at an offset are crucial in understanding the stability of inkjet printed patterns, which find application in organic flexible electronic devices. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PEDOT PSS) dispersion in water is a widely used commercial conducting polymer for the fabrication of electron devices. The effects of droplet spacing, impact velocity, substrate hydrophilicity, polymer concentration, and charges on the coalescence of two sessile droplets have been experimentally investigated, and the characteristics of dynamic spreading during the coalescence process are determined through image processing. The equilibrium spreading length of the coalesced droplets decreases with concentration and spacing of the droplets, revealing the necessity of optimum fluid properties (viscosity and surface tension) for the stability of the desired pattern. The droplets impact energy governs the maximum extent of spreading and receding dynamics, as the velocity gradients developed in polymer droplets during coalescence are a function of the inertia of the fluid elements. Hydrophilicity affects the maximum spreading extent but it has no influence on the equilibrium droplet diameter. The spreading length dynamics of charge-neutralized PEDOT PSS is found similar to the charged droplets, which show that the charged nature of the polymer does not affect the coalescence behavior. Furthermore, different spreading regimes are identified and the governing forces in each regime are described using a semianalytical formulation derived for the coalescence of two droplets. The model has been found to accurately provide insight into the various mechanisms that play a role during the complex spreading event.

Electromechanical Behavior of Conductive Polyaniline/Poly (Vinyl Alcohol) Blend Films Under Uniaxial Loading

Polyaniline (PANI) an electronically conducting polymer, and its charge transfer complexes are interesting engineering materials due to their unique electronic conductivity, electrochemical behavior, low raw material cost, ease of synthesis and environmental stability in comparison with other conjugated polymers. The main disadvantage of PANI is its limited processability. Blending of conducting polymers with insulating polymers is a good choice to overcome the processability problem. In this study a solution-blend method is adopted to prepare conductive polyaniline/polyvinyl alcohol (PANI/PVA) blend films at various blend ratios. Interest in applications for polyaniline (PANI) has motivated investigators to study its electro mechanical properties, and its use in polymer composites or blends with common polymers. The work described here looks at the uniaxial deformation behavior of the conducting polymer films and the anisotropic dependency of electrical conductivity of the blend films exposed to static and dynamic loading conditions. The relation between mechanical strain, electrical conductivity and film microstructure is investigated on PANI/PVA blend films.Copyright

Parametric studies for strontium separation and volume reduction of a simulated nuclear waste solution

ABSTRACT Volume reduction of a radioactive waste solution and recovery of the long-lived radionuclides are very much essential for effective nuclear waste management. A combination of complexation and nanofiltration for selective separation of strontium from a simulated Intermediate-Level Waste (ILW) solution has been studied. The advantages of nanofiltration membranes such as high retention, low operating pressure, and higher permeate flux were explored for the “concentrate and contain” strategy of waste management. An ethylenimine (EI) oligomer mixture containing primary, secondary, and tertiary amines as functional groups was used as a complexing ligand. The key process parameters, such as the EI concentration, feed pH, and initial strontium concentration, were optimized for strontium rejection. Statistical design of experiments was adopted to study the individual effects and combined interaction effects of these parameters. The optimization of these process parameters for strontium rejection and permeate flux was carried out using central composite design (CCD). The EI concentration and feed pH showed significant but opposing effects on strontium rejection and permeate flux. A strontium rejection of 98% was obtained for an EI concentration of 2.85 g/l and a feed pH of 8. The volume of the strontium-containing waste solution was successfully reduced to 10% of the initial volume.

Solvent Induced Shape Memory Behaviour of Sulfonated Poly Ether Ether Ketone (SPEEK)

Shape memory polymers (SMPs) are a widely studied class of materials due to their numerous applications in various fields of engineering. They find applications in deployable structures, biomedical devices, adaptive optical devices, sensors and actuators, in textiles etc. Recent studies have shown shape memory behavior in many polymers. Sulfonated poly ether ether ketone (SPEEK) is an ionic polymer which is being extensively studied for its application in fuel cells as a Proton Exchange Membrane (PEM) polymer due to its relatively higher thermal and mechanical stability over other PEMs in addition to proton transport. Recent studies on a sulfonated ionomer, Nafion® which has only one broad reversible phase transition, can show tunable, multiple shape memory effects by deforming the polymer at different temperatures without compromising the shape fixity (Rf). This paper reports, for the first time, the swelling (in solvents) induced shape memory behavior observed in SPEEK. The study was motivated by the preliminary observations of the response of SPEEK to solvent stimulus. SPEEK samples of varying degrees of sulfonation (DS) were prepared by the sulfonation of poly ether ether ketone (PEEK). The shape fixation and recovery rates (Rr) of the polymer under different temperatures and solvent conditions are reported. A comparative study of the shape memory response of the material with varying DS was also carried out. We also report for the first time the potential use of the parallel plate geometry of a rheometer for estimating the force during the shape recovery process. Visual demonstration of the shape memory effect is carried out using solvents at different temperatures.Copyright