Exploring the effect of radiation crosslinking on the physico‐mechanical,dynamic mechanical and dielectric properties of EOC–PDMS blends for cable insulation applications

This work focuses on the effect of electron beam irradiation on the physico‐mechanical, dynamic mechanical and dielectric properties of blends based on ethylene octene copolymer (EOC) and poly dimethyl siloxane (PDMS) rubber. It is found that electron beam irradiation caused considerable improvement in the physico‐mechanical properties; the tensile strength was enhanced by nearly 35% for 70:30 EOC:PDMS blend. Phase morphology of the blends analyzed before irradiation by scanning electron microscopy (SEM) exhibited droplet/matrix morphology with sizes of the PDMS rubber domain varying from 0.55 µm to 0.47 µm as the amount of PDMS rubber decreased from 30 wt% to 10 wt%. This reduction in the PDMS rubber domain has been correlated with the physico‐mechanical properties of the blends. Further, the dynamic mechanical properties and creep behavior of these EOC:PDMS blends before and after irradiation has been studied. It is inferred that the 70:30 blend after radiation crosslinking shows a 17% decrease in the creep compliance, i.e. higher creep resistance compared to neat blends. All the radiation crosslinked blends exhibited lower dielectric constant, lower dielectric loss and higher electrical resistivity as compared to the virgin blends which makes it suitable for cable insulating application. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of subphthalocyanines as probes for the accessibility of silica nanochannels

The synthesis of a new subphthalocyanine is reported. Its structural and photophysical properties are ideal for probing the accessibility of arrays of silica nanochannels.     

Physico-mechanical properties and biodegradation of oxo-degradable HDPE/PLA blends

Blends of high density polyethylene/poly(lactic acid) with/without compatibilizer and pro-oxidant (cobalt stearate) were prepared by melt blending technique. In ratio 80/20, the blend revealed a good combination of tensile properties and optimum poly(lactic acid) content. The improvement in mechanical properties of this blend was achieved by addition of 4 phr compatibilizer. Cobalt stearate (CoSt) was added to 80/20 blends in 0.1% and 0.2% (w/w) ratios. The obtained blends were characterized by DSC, SEM, FTIR spectroscopy, rheological study, etc. All the prepared blends were able to biodegrade in composting environment and the blend containing pro-oxidant was maximum degraded.     

A New Ultrasensitive Chromogenic Chelating Reagent for use in the Chromatographic Separation and Detection of Metal Ions

JPC – Journal of Planar Chromatography – Modern TLC - The heavy metal ions Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Bi3+, and Ag+ can be visualized as violet, black, green, yellow-green,...     

Effect of electron beam irradiation on dynamic mechanical,thermal and morphological properties of LLDPE and PDMS rubber blends

The effect of electron beam irradiation on the blends of linear low-density polyethylene (LLDPE) and poly dimethyl siloxane rubber (PDMS) prepared over a wide range of compositions starting from 70:30 to 30:70 (LLDPE: PDMS) by varying the radiation doses from 50 to 300 kGy has been studied. The dynamic modulii and dielectric strength of the blends increase on irradiation at 100 kGy as compared to that for the unirradiated blends. Degree of crystallinity and melting behaviour remain unchanged upon irradiation upto a dose of 100 kGy, beyond which it decreases. Thermal stability increases with increase in the proportion of PDMS rubber in the blend as well as on irradiation at 100 kGy. The phase morphology of the blends examined under the SEM exhibit two phase morphology before electron beam irradiation, whereas single phase morphology is observed after electron beam irradiation due to intra- as well as inter-molecular crosslinking leading to a miscible system.     

Thermally amendable tailor‐made functional polymer by RAFT polymerization and “click reaction”

This investigation reports the preparation and characterization of thermally amendable functional polymer bearing furfuryl functionality via reversible‐addition fragmentation and chain transfer (RAFT) polymerization and Diels‐Alder (DA) reaction. In this case, furfuryl methacrylate (FMA) was polymerized using 4‐cyano‐4‐[(dodecylsulfanylthiocarbonyl)sulfanyl] pentanoic acid as RAFT reagent and 4,4′‐azobis(4‐cyanovaleric acid) as thermal initiator. ¹H NMR, ¹³C NMR, and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry analysis showed that furfuryl group in poly(furfuryl methacrylate) (PFMA) was not affected during RAFT polymerization and the tailor‐made polymer had RAFT end group. The DA reaction was successfully carried out between the reactive furfuryl functionality of PFMA and different bismaleimides. The thermoreversible property of these DA polymers was characterized by FT‐IR and DSC analysis. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3365–3374     

Microspectroscopic analysis of green fluorescent proteins infiltrated into mesoporous silica nanochannels

The infiltration of enhanced green fluorescent protein (EGFP) into nanochannels of different diameters in mesoporous silica particles was studied in detail by fluorescence microspectroscopy at room temperature. Silica particles from the MCM-41, ASNCs and SBA-15 families possessing nanometer-sized (3-8 nm in diameter) channels, comparable to the dimensions of the infiltrated guest protein EGFP (barrel structure with dimensions of 2.4 nm × 4.2 nm), were used as hosts. We found that it is necessary to first functionalize the surfaces of the silica particles with an amino-silane for effective encapsulation of EGFP. We demonstrated successful infiltration of the protein into the nanochannels based on fluorescence microspectroscopy and loading capacity calculations, even for nanochannel diameters approaching the protein dimensions. We studied the spatial distributions of the EGFPs within the silica particles by confocal laser scanning microscopy (CLSM) and multimode microscopy. Upon infiltration, the fluorescence lifetime drops as expected for an emitter embedded in a high refractive index medium. Further, the spectral properties of EGFP are preserved, confirming the structural integrity of the infiltrated protein. This inorganic-protein host-guest system is an example of a nanobiophotonic hybrid system that may lead to composite materials with novel optical properties.     

Effect of Cloisite and modified Laponite clays on the rheological behavior of TPU–clay nanocomposites

The effect of nanoclays (modified Laponite and Cloisite) on the dynamic modulus, dynamic viscosity, and relaxation time of thermoplastic polyurethane (TPU)-based nanocomposites is studied by using the dynamic mechanical rheometer in strain, temperature, frequency sweeps, and stress relaxation experimental modes. Cloisite 20A preferentially associates to the soft domains and dodecyl amine-modified Laponite RD favors the hard domains of the TPU, whereas cetyl trimethyl ammonium bromide-modified Laponite RD does not show any preference and gets distributed both in the hard and soft domains randomly. Cloisite-based nanocomposites, having longer diskette size, possess greater dynamic modulus and viscosity than Laponite-based ones. The change in modulus and viscosity of the nanocomposites over the range of frequencies registers a completely different behavior at different temperature regimes depending on the size of diskettes of the nanoclays and their distribution (before and after the softening of the hard domains). Addition of clay is found to increase the elastic component of stress relaxation of the TPU at 120°C. This behavior is more prominent in the case of Cloisite-based nanocomposites as compared to their Laponite-based counterparts. The morphology correlates well with the dynamic rheological properties of these nanocomposites.     

Halogen-free flame retardant PUF: Effect of melamine compounds on mechanical, thermal and flame retardant properties

Water blown rigid polyurethane foam (PUF) was prepared with melamine polyphosphate (MPP) and melamine cyanurate (MC) as fire retardant (FR) additives. The effect of these additives on the properties of rigid PUF such as physico-mechanical, morphological, thermo-oxidative stability, flame retardancy and smoke density properties were studied. The mechanical and thermo-oxidative stability of PUF filled with MC was found to be better than those of MPP filled PUF. The insulation property of both MPP and MC filled PUF was improved with respect to the neat PUF. The FR properties of these filled PUF were evaluated by cone calorimeter, limiting oxygen index (LOI), smoke density, rate of burning and char residue estimation. The FR property of MPP filled PUF was better than that of the MC filled PUF.     

Kinetic investigation on the curing of ethylene methyl acrylate—Polydimethyl siloxane rubber blends by differential scanning calorimetry

Curing reactions of ethylene methyl acrylate (EMA) polydimethyl siloxane (PDMS) rubber blends have been investigated by differential scanning calorimetry (DSC) and by Rheometry. The curing exoterms obtained from DSC curves have been analysed to derive the kinetic parameters associated with the curing process. Crosslinking of EMA-PDMS rubber blends follow first order kinetics. The effect of blend ratio and peroxide concentration on the crosslinking characteristics of the blends have also been investigated. Department of Metallurgical Engineering