MECHANICAL OXIDATION OF MULTI-WALLED CARBON NANOTUBES AS A REPLACEMENT OF ACID OXIDATION METHOD

Priyanka Pandey,Smita Mohanty,SANJAY K. NAYAK 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.8

In the present study, a candid approach using mechanical oxidation, for modifcation of multiwalled carbon nanotubes (CNTs) has been utilized, and its advantages over conventional acid oxidation methods have been established. Higher concentration of acidic groups was found in case of mechanically oxidized CNTs (i.e., McCNT) as compared to acid oxidized CNT (i.e., ACNT). Raman spectrum exhibited greater degree of transformation of sp2 carbon into sp3 carbon. X-ray diffraction (XRD) analysis reveale maintained crystalline organization in McCNT. The major finding of the study was that, the mechanical oxidation method can be used easily to replace the conventional acid treatment method. This is because in the mechanical oxidation crystalline organization of CNTs can be maintained, relatively higher number of acid groups can be incorporated, no loss to the mass of CNTs is allowed etc.

Nanotoxicity of Rare Earth Metal Oxide Anchored Graphene Nanohybrid: A Facile Synthesis and In-Vitro Cellular Response Studies

Sriparna De,Smita Mohanty,Sanjay Kumar Nayak,Suresh K. Verma,Mrutyunjay Suar 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.6

Graphene, a single sp2 bonded carbon, is now a burgeoning interest with various fascinating properties in a large number of biomedical applications. Consequently, the impact of graphenebased functional nanohybrid and its potential risk to human health have raised considerable public concerns. In this present study, we have synthesized cerium oxide (CeO2) anchored reduced graphene oxide (RGO) nanohybrid and a detailed study on its nanotoxicity profile has also been scrutinized. To confirm the efficient synthesis of nano-CeO2/RGO nanohybrid, the systematic characterization has been carried out using FTIR, Raman and UV-Vis spectroscopic analysis. The successful imprint of CeO2 nanoparticles (NPs) on RGO nanosheet was also evident from the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs. A dose-dependent in vitro nanotoxicity of the nanohybrid has been assessed by using monocyte macrophage cells-Raw264.7 and colon cancer cells-HCT116 as compared with RGO and CeO2. The results conferred that as compared with single nanostructures (RGO or CeO2), nanohybrid showed excellent biocompatibility and no such prominence morphological alteration of the cell structure. Moreover, after exposure of different nanomaterials to HCT116 cells, the possible cellular interaction was investigated through reactive oxygen species (ROS) measurements using flow cytometry analysis dicholoro-dihydro-fluorescen dia-acetate (DCF) assay. These results conveyed that nanohybrid adapts an oxidative stress mechanism upon cellular interaction where it utilizes the scavenging property of CeO2, which induces the cell proliferation. Overall, the nano-CeO2/RGO nanohybrid exhibits a prolonged biocompatibility and cell viability, which is highly desired for biomedical applications.

Synthesis and Characterization of Vegetable Oil Based Polyurethane Derived from Low Viscous Bio Aliphatic Isocyanate: Adhesion Strength to Wood-Wood Substrate Bonding

Swarnalata Sahoo,Hemjyoti Kalita,Smita Mohanty,Sanjay Kumar Nayak 한국고분자학회 2017 Macromolecular Research Vol.25 No.8

In the current study, biobased polyurethane (PU) adhesives at three different stoichiometric ratios of hard (NCO) to soft segment (OH) (1.1:1, 1.3:1, 1.5:1) were prepared by reacting castor oil (CO) based polyol with partially biobased polyisocyanate (PBPI) in the presence of dibutyltin dilaurate (DBTDL) as catalyst. The synthesis of PU adhesive films such as CO-PU1.1:1, CO-PU1.3:1, and CO-PU1.5:1 was confirmed by Fourier transform infrared (FTIR) spectroscopy. The effect of stoichiometric ratios on the bonding strength of wood-to-wood substrate was studied using lap shear strength test. The change in lap shear strength of PU adhesive films subjected to acid and alkali solution was tested. The chemical resistance, surface properties and wetting energies of PU adhesive films were evaluated using scanning electron microscopy (SEM) analysis and contact angle measurement. Thermal stability and activation energy of the films were determined employing thermogravimetric analysis (TGA). The experimental result showed that CO-PU1.3:1 exhibited higher adhesive strength, where as CO-PU1.5:1 exhibited higher thermal stability.

Study of UV aging on the performance characteristics of vegetable oil and palm oil derived isocyanate based polyurethane

Sonalee Das,Priyanka Pandey,Smita Mohanty,Sanjay Kumar Nayak 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.2

The impact of UV aging on the characteristic properties of synthesized polyurethane (PUs) from castor oil and transesterified castor oil with palm oil based isocyanate and 1,4 butanediol was investigated at different exposure time of 0, 250, 500, 750 and 1,000 h, respectively. The aging properties of the PU films were analyzed through differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Tensile tests. The PU films derived from castor oil showed noticeable changes in chemical structure after 250 h of UV exposure owing to chain scission of the urethane group. A considerable decrease in the thermal and tensile properties of the developed PU films was observed due to the plasticization phenomenon. SEM micrographs revealed morphological changes through the appearance of cracks and blisters composed of primary amines on the surface of exposed PU films. However, PUs derived from transesterified castor oil with a higher hydroxyl value exhibited improved UV resistance characteristics due to higher crosslinking and degrade only after 750 h of exposure. Thus, the synthesized green PUs based on transesterified castor oil with palm oil based isocyanate compositions can be candidate materials for developing UV resistant coating material.

Effect of nanofillers on selectivity of high performance mixed matrix membranes for separating gas mixtures

Suchhanda Srabanee Swain,Lakshmi Unnikrishnan,Smita Mohanty,Sanjay Kumar Nayak 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.8

Techniques for separation of gas mixtures obtained from various sources, such as effluents from industries, and biogas, have always fascinated researchers. The advent of mixed matrix membranes (MMMs) has opened up a new window of opportunity for developing membranes coupled with flexibility, processability, and permeability of polymers and selectivity of inorganic nanomaterials. This review is a detailed overview of the effect of various nanofillers on the separation performance of MMMs including the major factors affecting the perm-selectivity and possible solutions for overcoming the emerging challenges. The paper also presents contemporary approaches for cost-effective implementation of MMMs. Methodologies for designing MMMs with improved interfacial morphology to exploit their full potential in tailoring the selectivity efficiency are also discussed in detail. This review can act be a guideline for the future development of high-performance MMMs for industrial applications without compromising long-term separation performance, durability, and stability to processing conditions.

Influence of thermally induced, dehydroxylated nanoclay on polymer nanocomposites

Priyanka Pandey,Sanjay Kumar Nayak,Smita Mohanty 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.8

This work reports a novel approach towards a chemical-free treatment of nanoclay through extensive thermalexposure. Dehydroxylation at high temperature was utilized to enhance the influence of nanoclay on the propertiesof polymer. The effect of this treatment of nanoclay, on the polymer properties, with reference to Polypropylene (PP)has been investigated. The FTIR spectra revealed the successful removal of water from the intergallery spacing of thenanoclay. The maintained structural configuration of the clay was confirmed using WAXD pattern. The uniform dispersionand exfoliation of thermally treated clay layers inside the polymer matrix was confirmed through enhancedmechanical properties. Improved crystallization properties, thermal stability and flame retardant characteristic werealso noticed in the nanocomposites reinforced with thermally dehydroxylated clay. This study revealed that the dehydroxylationapproach of modification of nanoclay may provide much enhanced properties of polymer, without involvementof any chemical for modification.

Biobased Epoxy Blends from Epoxidized Castor Oil: Effect on Mechanical, Thermal, and Morphological Properties

Sudha G. S.,Hemjyoti Kalita,Smita Mohanty,Sanjay Kumar Nayak 한국고분자학회 2017 Macromolecular Research Vol.25 No.5

In the present study, in-situ epoxidation was employed to prepare epoxidized castor oil (ECO). Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectra analysis were used to analyze the chemical structures of ECO. Biobased epoxy blends were synthesized from diglycidyl ether of bisphenol A (DGEBA) and ECO at variable wt% using triethylenetetramine as curing agent. The thermal, mechanical and morphological behavior of blends has been investigated. The morphological study showed homogeneous mixing of the ECO and DGEBA blends. The blend prepared using 20wt% of ECO showed optimum impact and flexural strength as compared with commercially available epoxy resin. The fracture toughness parameters, critical stress intensity (KIC) and the critical strain of blends were also observed to increase as compared with the virgin matrix which revealed enhancement in toughness. The tensile property of the blend reduced with the increasing ECO content which confirmed the fact that the addition of the high amount of ECO reduces the crosslink density of the biobased epoxy.

Thermokinetics behavior of epoxy adhesive reinforced with low viscous aliphatic reactive diluent and nano-fillers

Amit Kumar Singh,Bishnu Prasad Panda,Smita Mohanty,Sanjay Kumar Nayak,Manoj Kumar Gupta 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.11

The current study reports the effect of low viscous aliphatic reactive diluent (RD), MWCNT and VGCF on the curing kinetics of amine cured epoxy adhesive system employing non-isothermal differential scanning calorimetric (DSC) technique. Non-isothermal DSC thermograms of epoxy adhesive were studied at various heating rates: 5, 10 and 15 oC/min. The decrease in the exothermic peak height with the introduction of MWCNTs and VGCFs was taken as proof of the acceleration effect of nano-fillers on the epoxy-amine curing reaction. Also, increased Tonset, TP and ΔHcurs values were observed for epoxy/RD adhesive system at all heating rates. The value of activation energy (Ea) was determined using Kissinger and Flynn-Wall-Ozawa methods. Experimental results showed that the addition of 10 wt% RD increased the Ea from 60 to 63 kJ/mol on account of the reduced viscosity, allowing better contact of resin with the curing agent. Furthermore, MWCNTs have an accelerating effect on the cure kinetics that does not change the autocatalytic cure reaction mechanism of epoxy resin. It was also found that the addition of MWCNT and VGCF decreases the overall degree of conversion, as evident with lower ΔHcure and Ea of the cured adhesive when compared with epoxy/RD system. The dependency of Ea on degree of conversion ranging from α =0.1 to 0.9was also investigated. The two normalized functions y(α) and z(α) were also considered in order to study the complex curing mechanism. The kinetic parameters m, n and lnA were obtained by using two parameter autocatalytic Sestak-Berggren model. The curves revealed good agreement between experimentally determined and theoretically obtained MWCNT/VGCF reinforced epoxy adhesive systems.

Influence of Nanoclays and Nano-TiO2 on the Mechanical and Thermal Properties of Polycarbonate Nanocomposite

Jaya Vani. S,K Nayak,Smita Mohanty,M Rahail Parvaiz 한국고분자학회 2011 Macromolecular Research Vol.19 No.6

Polycarbonate (PC) nanocomposites were prepared using a melt intercalation technique with a series of organically modified clays and nano-TiO_2 (nTiO_2). The effect of the clay and nTiO_2 loading on the morphological,mechanical and thermal behavior of the PC nanocomposites was examined. The modulus enhancement was greater for the nanocomposite formed from PC with clay than the nTiO_2 nanocomposite. These nanocomposites also showed a significant decrease in tensile elongation and ductility with respect to nanoclays incorporation. The nTiO_2 nanocomposites also showed superior mechanical properties to the nanocomposite reinforced with nanoclay. The experimental results were compared with theoretical models. The thermal stability of PC and its nanocomposites were investigated by thermogravimetric analysis (TGA). The glass transition temperature was examined by differential scanning calorimetry (DSC). The incorporation of C30B improved the mechanical and thermal properties up to a 5wt% clay loading due to polar interactions between the PC matrix and the intercalant present in the C30B nanoclay. Wide angle X-ray diffraction (WAXD) showed an increase in the basal spacing of the C30B nanoclay confirming the presence of an intercalated structure. TEM confirmed the intercalation of a C30B clay layers and uniform dispersion of nTiO_2 particles in the PC matrix. The viscoelastic behavior examined by dynamic mechanical analysis (DMA) under a periodic stress revealed the stiffness of the PC nanocomposite in the presence of clay and n-TiO_2.

Synthesis and Characterization of Crosslinked Transparent Poly(ester-urethane-acrylate) Containing Methyl Methacrylate

Shyam Dev Maurya,Surendra K. Kurmvanshi,Smita Mohanty,Sanjay K Nayak 한국고분자학회 2017 Macromolecular Research Vol.25 No.9

The current study deals with the synthesis of various compositions of crosslinked poly(ester-urethane-acrylate) (PEUA)/methylmethacrylate (MMA) copolymer employing free radical polymerization. Initially, (1,4-butanediol) orthophthalate (BPE) polyester polyol has been synthesized by reacting 1,4 butanediol (BDO) and phthalic anhydride (PA). Subsequently the PEUA prepolymer was formed by reacting one mole of BPE with two mole of isophorone diisocyanate (IPDI) followed by end capping with two mole of 2-hydroxyethyl methacrylate (HEMA) in the presence of dibutyltin dilaurate (DBTL) catalyst. Finally, different compositions of crosslinked PEUA/MMA copolymer were prepared by reacting the PEUA prepolymer with MMA, in the presence of 1% azobisisobutyronitrile (AIBN) (w/w) as a chain initiator. The formation of BPE, PEUA and copolymers was confirmed by Fourier transform infrared (FT-IR) and 1H NMR spectroscopy. Water uptake, mechanical, thermal and optical properties of PEUA, PMMA and their copolymers have been also investigated. The impact fractured surface morphology of copolymers was observed using scanning electron microscope (SEM). The results showed that the increased miscibility, improved mechanical and physical properties of copolymer was influenced by the crosslink density. Dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), Haze and transparency of PEUA/MMAcopolymers were determined. The copolymer with 40wt% MMA loading exhibited optimum mechanical and physical properties with respect to the other compositions.