The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Niranjan Karak - One of the best experts on this subject based on the ideXlab platform.
-
tannic acid based tough hyperbranched epoxy thermoset as an advanced environmentally sustainable high performing material
Iranian Polymer Journal, 2016Co-Authors: Purnima Baruah, Rituparna Duarah, Niranjan KarakAbstract:Bio-based resources are progressively replacing those of petroleum-based to address the detrimental impact on environment and health issues. In this regard, hyperbranched epoxy resins with three different compositions were synthesized by simple polycondensation reaction of bio-based branching reactant, diethanolamide of gallic acid with bisphenol-A, and epichlorohydrin. Diethanolamide of gallic acid was obtained from the reaction between tannic acid and diethanol amine in the presence of sodium methoxide catalyst. FTIR, 1H NMR, and 13C NMR spectroscopic analyses were employed to confirm the structure of branching unit and hyperbranched resins. Poly(amido amine)-cured hyperbranched epoxy thermosets exhibited superior properties, such as tensile strength (45–57.2 against 38.5 MPa), elongation-at-break (16.3–24.2 against 5 %), Scratch Hardness (>10 against 7 kg), toughness (577.8–859.1 against 150.2 MPa), tensile adhesive strength (1647–2086 against 581 MPa), and biodegradability (17.6–31 against 2.2 %), compared with the conventional bisphenol-A-based epoxy, prepared under the same conditions. These results simply indicate the advantageous of the bio-based moiety and hyperbranched architecture on the overall performance of the thermosets. Moreover, good antioxidative response of these thermosets expands their applications as protective coatings and adhesive materials. Thus, diethanolamide of gallic acid-based hyperbranched epoxy thermoset can be used as potent ecofriendly advanced material in multifaceted applications.
-
bio based waterborne polyurethane carbon dot nanocomposite as a surface coating material
Progress in Organic Coatings, 2016Co-Authors: Biplab Ghosh, Satyabrat Gogoi, Suman Thakur, Niranjan KarakAbstract:Abstract Waterborne surface coating materials with low volatile organic compounds (VOCs) are environmentally friendly and hence the most desired materials for the modern society. The present study reports in situ fabricated thermosetting hyperbranched waterborne polyurethane (WPU)/carbon dot (CD) nanocomposites as surface coating materials. CD was used as a nanoreinforcing agent (at 0.25, 0.5 and 1.0 weight percentages) in the nanocomposites. The structures of the waterborne polyurethane and its fabricated thermosetting nanocomposites were analyzed by using different spectroscopic and analytical tools like Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, UV–visible spectroscopy and X-ray diffractometry. The mechanical properties of the pristine thermosetting WPU were significantly improved after incorporation of CD (tensile strength from 4.5 to 8.5 MPa, elongation at break value from 96 to 136%, Scratch Hardness from 3 to 9 kg, impact strength from 70 to 100 cm). The thermal stability of WPU also enhanced from 250 to 280 °C after incorporation of CD in the matrix. Interestingly, the fabricated nanocomposites demonstrated an excitation wavelength and concentration dependent photoluminance behavior as well as exhibited good transparency. Thus, the fabricated WPU nanocomposites show great potential as low VOC containing environment friendly transparent surface coating material.
-
a starch based sustainable tough hyperbranched epoxy thermoset
RSC Advances, 2015Co-Authors: Rituparna Duarah, Niranjan KarakAbstract:With the growing concern of long term environmental and waste management problems, the recent trend in the polymer industry is aimed to utilize environmentally benign substrates for development of sustainable polymers with the required properties for their potential applications as substitutes for petrochemical derivatives. In this arena, the authors aspired to use starch, a natural renewable polysaccharide obtained from a wide variety of crops, as one of the reactants for a one-pot synthesis of a bio-based sustainable hyperbranched epoxy resin. Nuclear magnetic resonance (1H NMR and 13C NMR), Fourier transformed infrared spectroscopy (FTIR) along with different analytical techniques confirmed the chemical structure of the resin. The poly(amido amine) cured epoxy thermoset exhibited acceptable biodegradation along with desirable properties. It exhibits excellent impact resistance (>100 cm), outstanding Scratch Hardness (>10 kg), exceptionally high tensile adhesive strength (up to 2906 MPa for aluminum), moderate tensile strength (up to 29 MPa), good elongation at break (up to 38%), high toughness (up to 8.40 MJ m−3) and very good chemical resistance against a number of chemical environments. Moreover, the thermoset displayed potent biomedical attributes by exhibiting cytocompatibility with erythrocytes as assessed through a hemolytic assay. Thus, the synthesized eco-friendly and sustainable hyperbranched epoxy thermoset with good toughness and exceptional adhesive strength can be a worthy replacement for petroleum-based epoxy thermosets as an advanced engineering material.
-
biobased biodegradable waterborne hyperbranched polyurethane as an ecofriendly sustainable material
ACS Sustainable Chemistry & Engineering, 2014Co-Authors: Satyabrat Gogoi, Niranjan KarakAbstract:Research thrust to address the problems confronting the use of conventional polymers like high volatile organic compound (VOC) content still remains a challenge. In this context, the authors report the synthesis of a sustainable and biodegradable waterborne hyperbranched polyurethane (WHPU) using polyphenolic tannic acid in lieu of vegetable oil as the biobased component. The chemical structure of WHPU was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. An UV–visible peak at the wavelength of 282 nm confirmed the presence of catechol moiety in WHPU. WHPU exhibited pronounced thermostability and desirable performance (tensile strength, 6.87 MPa; elongation at break, 315%; Scratch Hardness, 5.5 kg for 15 wt % tannic acid based WHPU). The radical scavenging and hemolytic assays of WHPU showed their potent antioxidant activity and cytocompatibility with the erythrocytes, respectively. Furthermore, WHPU exhibited bacterial degradation by Pseudomonas aeruginosa. Thus, th...
-
biodegradable hyperbranched epoxy from castor oil based hyperbranched polyester polyol
ACS Sustainable Chemistry & Engineering, 2014Co-Authors: Bibekananda De, Manabendra Mandal, Kuldeep Gupta, Niranjan KarakAbstract:An outstanding tough, highly elastic, biodegradable, and thermostable hyperbranched epoxy was synthesized by a simple polycondensation reaction between a castor oil-based hyperbranched polyester polyol (HBPP) of monoglyceride of oil and bis(hydroxy methyl)propionic acid (Bis-MPA) and in situ-generated diglycidal ether of bisphenol A (DGEBA). The structure of HBPP was confirmed from FTIR, NMR, and different analytical studies. The formation of hyperbranched epoxy along with its structure was analyzed by different spectroscopic and analytical techniques. The poly(amido amine)-cured hyperbranched epoxy exhibited high tensile strength (42 MPa), extensibility (88% elongation), toughness (3144), Scratch Hardness (>10.0 kg), impact resistance (>100 cm), flexibility (bent up to 180° without damage), and biodegradation. The results indicate the strong influence of the amount of polyester polyol and bisphenol A on the performance of the thermosets. The study showed the superiority of the studied hyperbranched epoxy...
Yencon Hung - One of the best experts on this subject based on the ideXlab platform.
-
effect of binder on the physical stability and bactericidal property of titanium dioxide tio2 nanocoatings on food contact surfaces
Food Control, 2015Co-Authors: Veerachandra K Yemmireddy, Yencon HungAbstract:TiO2 is a promising photocatalyst for use in food processing environment as an antimicrobial coating. The purpose of this study was to determine the effect of different binding agents on the physical stability and bactericidal property of TiO2 nanocoatings created on stainless steel surfaces. A total of six different coating suspensions were prepared by mixing TiO2 (Aeroxide® P-25) nanoparticles (NPs) with three different types of binders (Shellac (A), polyuretahne (B), and polycrylic (C)) at a 1:4 to 1:16 NP to binder weight ratio. Bactericidal activity of these TiO2 coatings against Escherichia coli O157:H7 (5-strain) was determined at three different UV-A light intensities (0.25, 0.50 and 0.75 mW/cm2) for 3 h. The type of binder used in the coating had a significant effect on the log reduction of E. coli O157:H7. TiO2 coatings with binder C showed highest reduction (>4 log CFU/cm2) followed by TiO2 coating with binder B and A. Increasing the binder concentration in the formulation from a 1:4 to 1:16 weight ratio decreased the log reduction of E. coli O157:H7. Increasing the UV-A light intensity from 0.25 to 0.75 mW/cm2 increased the log reduction of bacteria for all the TiO2 coatings. The physical stability of the TiO2 coatings was determined using ASTM procedures. TiO2 coatings with binder B showed highest adhesion strength and Scratch Hardness when compared to coatings with other binders. However, on repeated use experiments (1, 3, 5, and 10 times), TiO2 coatings with binder C were found to be physically more stable and able to retain their original bactericidal property. The results of this study showed promise in developing durable TiO2 coatings with strong photocatalytic bactericidal property on food contact surfaces using appropriate binding agents to help ensure safe food processing environment.
-
development of titanium dioxide tio2 nanocoatings on food contact surfaces and method to evaluate their durability and photocatalytic bactericidal property
Journal of Food Science, 2015Co-Authors: Veerachandra K Yemmireddy, Glenn Farrell, Yencon HungAbstract:Titanium dioxide (TiO2) is a well-known photocatalyst for its excellent bactericidal property under UVA light. The purpose of this study was to develop physically stable TiO2 coatings on food contact surfaces using different binding agents and develop methods to evaluate their durability and microbicidal property. Several types of organic and inorganic binders such as polyvinyl alcohol, polyethylene glycol, polyurethane, polycrylic, sodium and potassium silicates, shellac resin, and other commercial binders were used at 1:1 to 1:16 nanoparticle to binder weight ratios to develop a formulation for TiO2 coating on stainless steel surfaces. Among the tested binders, polyurethane, polycrylic, and shellac resin were found to be physically more stable when used in TiO2 coating at 1:4 to 1:16 weight ratio. The physical stability of TiO2 coatings was determined using adhesion strength and Scratch Hardness tests by following standard ASTM procedures. Further, wear resistance of the coatings was evaluated based on a simulated cleaning procedure used in food processing environments. TiO2 coating with polyurethane at a 1:8 nanoparticle to binder weight ratio showed the highest Scratch Hardness (1.08 GPa) followed by coating with polycrylic (0.68 GPa) and shellac (0.14 GPa) binders. Three different techniques, namely direct spreading, glass cover-slip, and indented coupon were compared to determine the photocatalytic bactericidal property of TiO2 coatings against Escherichia coli 0157:H7 at 2 mW/cm2 UVA light intensity. Under the tested conditions, the indented coupon technique was found to be the most appropriate method to determine the bactericidal property of TiO2 coatings and showed a reduction of 3.5 log CFU/cm2 in 2 h. Practical Application A simple approach to create physically stable and bactericidal TiO2 nanocoatings was developed on food contact surfaces of stainless steel using different binding agents. The developed TiO2 nanocoatings might help to minimize microbial cross-contamination and ensure safe food processing environment.
Rituparna Duarah - One of the best experts on this subject based on the ideXlab platform.
-
tannic acid based tough hyperbranched epoxy thermoset as an advanced environmentally sustainable high performing material
Iranian Polymer Journal, 2016Co-Authors: Purnima Baruah, Rituparna Duarah, Niranjan KarakAbstract:Bio-based resources are progressively replacing those of petroleum-based to address the detrimental impact on environment and health issues. In this regard, hyperbranched epoxy resins with three different compositions were synthesized by simple polycondensation reaction of bio-based branching reactant, diethanolamide of gallic acid with bisphenol-A, and epichlorohydrin. Diethanolamide of gallic acid was obtained from the reaction between tannic acid and diethanol amine in the presence of sodium methoxide catalyst. FTIR, 1H NMR, and 13C NMR spectroscopic analyses were employed to confirm the structure of branching unit and hyperbranched resins. Poly(amido amine)-cured hyperbranched epoxy thermosets exhibited superior properties, such as tensile strength (45–57.2 against 38.5 MPa), elongation-at-break (16.3–24.2 against 5 %), Scratch Hardness (>10 against 7 kg), toughness (577.8–859.1 against 150.2 MPa), tensile adhesive strength (1647–2086 against 581 MPa), and biodegradability (17.6–31 against 2.2 %), compared with the conventional bisphenol-A-based epoxy, prepared under the same conditions. These results simply indicate the advantageous of the bio-based moiety and hyperbranched architecture on the overall performance of the thermosets. Moreover, good antioxidative response of these thermosets expands their applications as protective coatings and adhesive materials. Thus, diethanolamide of gallic acid-based hyperbranched epoxy thermoset can be used as potent ecofriendly advanced material in multifaceted applications.
-
a starch based sustainable tough hyperbranched epoxy thermoset
RSC Advances, 2015Co-Authors: Rituparna Duarah, Niranjan KarakAbstract:With the growing concern of long term environmental and waste management problems, the recent trend in the polymer industry is aimed to utilize environmentally benign substrates for development of sustainable polymers with the required properties for their potential applications as substitutes for petrochemical derivatives. In this arena, the authors aspired to use starch, a natural renewable polysaccharide obtained from a wide variety of crops, as one of the reactants for a one-pot synthesis of a bio-based sustainable hyperbranched epoxy resin. Nuclear magnetic resonance (1H NMR and 13C NMR), Fourier transformed infrared spectroscopy (FTIR) along with different analytical techniques confirmed the chemical structure of the resin. The poly(amido amine) cured epoxy thermoset exhibited acceptable biodegradation along with desirable properties. It exhibits excellent impact resistance (>100 cm), outstanding Scratch Hardness (>10 kg), exceptionally high tensile adhesive strength (up to 2906 MPa for aluminum), moderate tensile strength (up to 29 MPa), good elongation at break (up to 38%), high toughness (up to 8.40 MJ m−3) and very good chemical resistance against a number of chemical environments. Moreover, the thermoset displayed potent biomedical attributes by exhibiting cytocompatibility with erythrocytes as assessed through a hemolytic assay. Thus, the synthesized eco-friendly and sustainable hyperbranched epoxy thermoset with good toughness and exceptional adhesive strength can be a worthy replacement for petroleum-based epoxy thermosets as an advanced engineering material.
R Subasri - One of the best experts on this subject based on the ideXlab platform.
-
effect of plasma surface treatment and heat treatment ambience on mechanical and corrosion protection properties of hybrid sol gel coatings on aluminum
Surface & Coatings Technology, 2010Co-Authors: R Subasri, A Jyothirmayi, D S ReddyAbstract:Abstract Hybrid sol–gel coatings derived from a base catalyzed hydrolysis of tetraethylorthosilicate and methyltriethoxysilane were deposited on aluminum substrates by a dip coating technique. Some of the coatings were deposited on substrates whose surfaces were pre-treated using atmospheric-air plasma prior to coating in order to study the effect of surface activation by plasma pre-treatment. The coated substrates were heat treated in different ambiences like air, flowing N 2 and vacuum to see the effect of heat treatment ambience on the properties of the coatings. Characterization of the coatings after heat treatment was carried out with respect to coating thickness, pencil Scratch Hardness, adhesion, water contact angle and their microstructure. Corrosion testing for all the coatings was carried out by electrochemical polarization measurements as well as electrochemical impedance spectroscopy in 3.5% NaCl solution for 1 h exposure time to investigate on their corrosion resistance. Coating thicknesses ranging from 1 μm–5 μm were obtained by varying the withdrawal speeds. Heat treatment in a controlled atmosphere with low oxygen content was seen to improve the hydrophobicity of coated surface, as measured by water contact angles (20 o — air; 71 o — N 2 ; 95 o — vacuum), thereby improving the corrosion resistance. Surface pre-treatment using open-air plasma was seen to improve the adhesion of the sol–gel coatings thus making it possible to obtain adherent and thick coatings in a single dip coating process. Both the methods of processing the coatings reduced the corrosion rate of aluminum from 1.95 mpy to 0.004 mpy in case of coatings densified in nitrogen and to 0.00068 mpy for coatings deposited on a plasma treated substrate and densified in air.
-
effect of plasma surface treatment on mechanical and corrosion protection properties of uv curable sol gel based gpts zro2 coatings on mild steel
Surface & Coatings Technology, 2010Co-Authors: P Kiruthika, R Subasri, A Jyothirmayi, K Sarvani, Neha Y HebalkarAbstract:Abstract Hybrid sol-gel based nanocomposite coatings derived from hydrolysis and condensation of a photopolymerizable silane precursor 3-Glycidoxypropyltrimethoxy silane in combination with zirconium-n-propoxide were deposited on mild steel substrates by a dip coating technique. In some cases, substrates were subjected to an atmospheric air–plasma surface pre-treatment prior to coating deposition. The coatings were subsequently densified by exposure to ultraviolet radiation followed by a thermal treatment at 250 °C. Characterization of the coatings with respect to thickness, water contact angle, pencil Scratch Hardness, adhesion and abrasion resistance was carried out. Corrosion testing was carried out on the coatings for a 1 h exposure to a 3.5% NaCl solution by electrochemical polarization and impedance measurements. The hybrid sol-gel coatings were found to improve the mechanical properties and corrosion resistance of mild steel. Plasma surface pre-treatment was found to improve the adhesion of coatings significantly and decreased the corrosion rate from 0.2652 mpy obtained for coatings without any surface pre-treatment to 0.0015 mpy, which was nearly 600 times lower than that of bare mild steel.
R D K Misra - One of the best experts on this subject based on the ideXlab platform.
-
Scratch deformation behavior of thermoplastic materials with significant differences in ductility
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: R S Hadal, R D K MisraAbstract:Abstract A comparative study of the Scratch deformation behavior of neat ethylene–propylene copolymers and polypropylene with significant differences in ductility is made by combining morphological examination by electron microscopy and Scratch deformation parameters by atomic force microscopy. Also, the deformation behavior during Scratch tests is examined for their respective long and short chain polymers. The ability of polymeric materials to resist Scratch deformation under identical Scratch test conditions follows the sequence (from maximum resistance to minimum resistance): short chain polypropylene > long chain polypropylene > short chain ethylene–propylene > long chain ethylene–propylene. The Scratch tracks in ethylene–propylene copolymers were characterized by a consecutive parabolic pattern containing voids, while polypropylenes exhibited zig-zag periodic Scratch tracks. The greater plastic flow in ethylene–propylene copolymers is encouraged by the high ductility of the copolymer and the ability to nucleate microvoids. The quasi-static periodic Scratch tracks are a consequence of sequential accumulation and release of tangential force and represents the stick–slip process. The susceptibility to Scratch deformation is discussed in terms of modulus, elastic recovery, Scratch Hardness, and entanglement density of polymeric materials. A higher effective entanglement density and percentage crystallinity of short chain polymers is helpful in enhancing Scratch resistance as compared to their respective long chain polymers.
-
on the Scratch deformation of micrometric wollastonite reinforced polypropylene composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Aravind Dasari, J Rohrmann, R D K MisraAbstract:Scratch deformation characteristics of neat and wollastonite-containing polypropylenes under identical test conditions are examined by electron microscopy and atomic force microscopy techniques. The study indicates that the severity of plastic deformation during Scratch deformation in filled polypropylenes is a strong function of the debonding/detachment of wollastonite mineral particles from the polypropylene matrix. Scratch resistance is evaluated in terms of Scratch Hardness, Scratch depth, average Scratch roughness, thickness and density of the Scratch tracks. Atomic force microscopy suggests the presence of a localized region surrounding the reinforcement particle that is characterized by enhanced crystal nucleation in which the local chain conformation and kinetics are likely to be different from regions that are a significant distance away from the mineral particle.
