A. Sujith

Imaging the cell wall of living single yeast cells using surface-enhanced Raman spectroscopy

The surface of a living yeast cell (Saccharomyces cerevisiae strain W303-1A) has been labeled with silver (Ag) nanoparticles that can form nanoaggregates which have been shown to have surface-enhanced Raman scattering (SERS) activity. The cell wall of a single living yeast cell has been imaged by use of a Raman microspectroscope. The SERS spectra measured from different Ag nanoaggregates were found to be different. This can be explained on the basis of detailed spectral interpretation. The SERS spectral response originates from mannoproteins which cover the outermost regions of the yeast cell wall. Analysis of SERS spectra from the cell wall and the extracted mannoproteins from the yeast has been performed for the clarification of variation in SERS spectra.

Sorption and Mechanical Properties of Nitrile Rubber Compatibilized Natural Rubber-Poly (Ethylene-Co-Vinyl Acetate) Blends

Acrylonitrile butadiene rubber (NBR) has been used as a compatibilizer for natural rubber—poly (ethylene-co-vinyl acetate) (NR—EVA) blends, vulcanized by sulfur. A significant reduction in solvent uptake is observed for compatibilized samples. This has been explained in terms of the increased interfacial adhesion between NR and EVA components of the blends in the presence of the compatibilizer. The threshold compatibilizer loading has been found to be 6 phr. The observed sorption features have been complemented by the evaluation of the surface morphology and mechanical properties of the blends. The kinetics of transport process through the compatibilized blends has also been discussed.

Organic vapor permeation through membranes based on ethylene propylene diene monomer and polyvinyl chloride

Composite membranes based on ethylene propylene diene monomer (EPDM) and polyvinyl chloride (PVC) has been prepared. The vapor permeation studies were conducted with aromatic hydrocarbons and aliphatic alcohols for the membrane characterization. Special attention has been given to the amount of PVC in the membrane, size of penetrant and also type of vulcanization. The permeability was found to decrease with increase in PVC content due to the stiff and rigid nature of PVC. The field emission scanning electron microscopy of the membranes showed a two-phase morphology. Here, the PVC is dispersed in the continuous EPDM phase. It was found that the permeability decreased with increase in the size of the penetrant. Different types of miscible liquid mixtures have been analyzed for finding out the separation efficiency of the membranes. In the case of benzene/propanol mixture, it has been found that when the concentration of benzene increases, the vapor permeation rate increases, indicating high interaction of benzene toward the composites.

Transport and mechanical properties of styrene butadiene rubber/ethylene vinyl acetate blends

Experimental results of sorption and desorption, obtained by a gravimetric method, have been presented for styrene butadiene rubber/ethylene vinyl acetate (SBR/EVA) blends with dichloromethane, chloroform and carbon tetrachloride as penetrants at 26°, 36° and 46 °C. The blends were crosslinked by using three different vulcanising systems viz. sulphur, peroxide, and a mixed system consisting of sulphur and peroxide. The liquid uptake tendency has been found to decreases with increase in EVA content in the blends. Transport parameters such as diffusivity, sorptivity and permeability were estimated. Attempts have been made to correlate the transport properties with the morphology of the blends. To examine the stability of the blends in solvent environment, mechanical testing was carried out for unswollen, swollen, and deswollen samples. An overall decrease in stress, strain, and elongation at break have been observed after a sorption-desorption cycle. The sorption results have been compared with relevant theoretical models.

Effect of unsaturation on physicochemical properties of maleic anhydride–grafted acrylonitrile butadiene styrene terpolymer:

In order to find out the shift of ductile nature of acrylonitrile-butadiene-styrene (ABS) polymer to brittle nature while maleic anhydride (MA) grafting, the iodine value of different MA-grafted ABS (MA-g-ABS) sampled has been determined. The iodine value of thermoplastic polymer is found by Wijs method with slight modification to overcome the poor solubility of thermoplastics in tetrachloromethane. Different samples with varying MA content were prepared using internal mixer. All the specimens were characterized by attenuated total reflectance IR spectroscopy and X-ray diffraction analysis. The iodine value measurements revealed that grafting and cross-linking evidently reduced the unsaturation in ABS polymer matrix. The grafting of MA causes the decrease in impact strength, flexural modulus, and a significant increase in crystallinity, tensile strength, yield point, and flexural strength, whereas thermal stability remains intact. Field emission scanning electron microscope images showed noticeable difference in broken surface texture between ABS and grafted samples.

Interactions of some liquid fuels with EPDM/PVC system

Composites based on Ethylene Propylene Diene Monomer (EPDM) and Poly Vinyl Chloride (PVC) has been prepared by static and dynamic vulcanization techniques. The effect of PVC as a filler on interactions of EPDM with three fuels viz; petrol, kerosene and diesel has been studied. The solvent transport was found to decrease with increase in PVC content in the composites. Diesel showed the lowest interaction with the composites compared to petrol and kerosene. The effect of cross linking system and the type of vulcanization on the swelling behavior has also been studied.

Compatibilisation of heterogeneous styrene butadiene rubber/poly(ethylene-co-vinyl acetate) blends

The compatibilisation of styrene butadiene rubber (SBR) and poly(ethylene–covinyl acetate) (EVA) blends with maleic-anhydride grafted poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS-g-MA) triblock copolymer has been investigated. The introduction of SEBS-g-MA resulted in an improvement in the mechanical properties of the blends with a reduction in damping characteristics, indicating the presence of efficient interfacial bonding. The optimum loading of SEBS-g-MA for SBR/EVA blends, has been found to be 6 phr. The better mechanical performance has been observed to be achieved for the compatibilised blends with DCP as curing agent. The results have been complemented by the studies using scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). It has also been found that the compatibilisation with SEBS-g-MA improved the thermal ageing characteristics of SBR/EVA systems.