15 results on '"Joby J. Kochumalayil"'
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2. Nanostructurally Controlled Hydrogel Based on Small‐Diameter Native Chitin Nanofibers: Preparation, Structure, and Properties
- Author
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Joby J. Kochumalayil, Qi Zhou, Nicholas Tchang Cervin, Ngesa Ezekiel Mushi, and Lars Berglund
- Subjects
Materials science ,Small diameter ,Compressive Strength ,General Chemical Engineering ,Chitin ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,nanofibers ,Polymer chemistry ,Environmental Chemistry ,General Materials Science ,Porosity ,Full Paper ,Molecular Structure ,Hydrogels ,Full Papers ,021001 nanoscience & nanotechnology ,compression ,0104 chemical sciences ,General Energy ,Chemical engineering ,chemistry ,Nanofiber ,Self-healing hydrogels ,rheology ,hydrogel ,0210 nano-technology - Abstract
Chitin nanofibers of unique structure and properties can be obtained from crustacean and fishery waste. These chitin nanofibers have roughly 4 nm diameters, aspect ratios between 25–250, a high degree of acetylation and preserved crystallinity, and can be potentially applied in hydrogels. Hydrogels with a chitin nanofiber content of 0.4, 0.6, 0.8, 1.0, 2.0, and 3.0 wt % were successfully prepared. The methodology for preparation is new, environmentally friendly, and simple as gelation is induced by neutralization of the charged colloidal mixture, inducing precipitation and secondary bond interaction between nanofibers. Pore structure and pore size distributions of corresponding aerogels are characterized using auto‐porosimetry, revealing a substantial fraction of nanoscale pores. To the best of our knowledge, the values for storage (13 kPa at 3 wt %) and compression modulus (309 kPa at 2 wt %) are the highest reported for chitin nanofibers hydrogels.
- Published
- 2016
3. Xyloglucan coating for enhanced strength and toughness in wood fibre networks
- Author
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Albert Serra, Fabiola Vilaseca, and Joby J. Kochumalayil
- Subjects
Toughness ,Nanocomposite ,Materials science ,Polymers and Plastics ,Bond strength ,Organic Chemistry ,Composite number ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Xyloglucan ,chemistry.chemical_compound ,chemistry ,Ultimate tensile strength ,Materials Chemistry ,Composite material ,Cellulose ,0210 nano-technology ,Wood fibre - Abstract
In recent times, cellulosic materials are witnessing strong interest from both industry and academia for their ability to progress in high-value products with green stamp. Besides the renewability and biodegradability appeal, exceptional properties such as mechanical strength together with toughness are pursued. In the present work, wood fibre networks from eucalyptus Kraft pulp fibres and cellulose nanofibres are combined to produce nanostructured composite networks with outstanding mechanical behaviour. For this purpose, xyloglucan (XG) polymer is adsorbed on cellulose nanofibres (CNF) forming core-shell CNF fibrils in hydrocolloidal suspension which is used to dramatically strengthen wood fibre networks. TEMPO-CNF at two different oxidation levels were coated with XG. The exceptional Young’s modulus and tensile strength found for fibre networks with only 10 wt% CNF was attributed to the fibre-fibre bond strength with better homogeneous stress distribution at the micro/nano scale. The production, mechanical characterization and structure analysis of such bionanocomposites is here presented.
- Published
- 2020
4. Water-soluble hemicelluloses for high humidity applications – enzymatic modification of xyloglucan for mechanical and oxygen barrier properties
- Author
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Joby J. Kochumalayil and Lars Berglund
- Subjects
chemistry.chemical_classification ,Polymer ,engineering.material ,Pollution ,Xyloglucan ,Hildebrand solubility parameter ,Oxygen permeability ,Oxygen transmission rate ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,engineering ,Environmental Chemistry ,Organic chemistry ,Relative humidity ,Biopolymer ,Solubility - Abstract
Bio-based polymers are of increasing interest in packaging applications as alternatives to petroleum-based polymers. Xyloglucan (XG) derived from tamarind seed waste was recently explored as a high performance biopolymer for packaging applications. Xyloglucan films have high strength, stiffness and oxygen barrier performance, but suffer from limitations in properties under high humidity conditions. This aspect is addressed in the present work using XG modification by enzymatic removal of side chain galactose residues. The modified XG was characterized using carbohydrate analysis and MALDI-TOF MS analysis for sugar and oligosaccharide compositions respectively. The consequence of galactose removal for XG chain packing was theoretically predicted using a group contribution method and the estimation of Hansen's solubility parameters. The properties of films made from modified XG in terms of tensile, oxygen transmission rate, and thermo-mechanical behaviour were measured and related to the structure of modified XGs. Modified XG films preserved the Young's modulus at high humidity at a level of 4.3 GPa at 92% relative humidity. Moreover, the oxygen permeability of modified XG samples was very low and was about 1.5 cc μm [m2 day]−1 kPa−1 at 80% relative humidity, more than 80% lower than that for native XG. The main reason is that modified XG absorbs less moisture, due to a decreased solubility. Decreased free volume may also contribute, as galactose residues are removed and XG branches become shorter.
- Published
- 2014
5. Regioselective modification of a xyloglucan hemicellulose for high-performance biopolymer barrier films
- Author
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Joby J. Kochumalayil, Qi Zhou, Wakako Kasai, and Lars A. Berglund
- Subjects
Materials science ,Polymers and Plastics ,Starch ,engineering.material ,chemistry.chemical_compound ,Biopolymers ,Polysaccharides ,Tensile Strength ,Spectroscopy, Fourier Transform Infrared ,Tamarindus ,Materials Chemistry ,Transition Temperature ,Organic chemistry ,Hemicellulose ,Cellulose ,Glucans ,chemistry.chemical_classification ,Molecular Structure ,Hydrolysis ,Organic Chemistry ,Water ,Polymer ,Dynamic mechanical analysis ,Biomechanical Phenomena ,Oxygen ,Xyloglucan ,Thermogravimetry ,chemistry ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,Seeds ,Chromatography, Gel ,engineering ,Xylans ,Biopolymer ,Oxidation-Reduction - Abstract
Biobased polymers such as starch and hemicelluloses from wood are of interest for packaging applications, but suffer from limitations in performance under moist conditions. Xyloglucan from industrial tamarind seed waste offers potential, but its Tg is too high for thermal processing applications. Regioselective modification is therefore performed using an approach involving periodate oxidation followed by reduction. The resulting polymer structures are characterized using MALDI-TOF-MS, size-exclusion chromatography, FTIR and carbohydrate analysis. Films are cast from water and characterized by thermogravimetry, dynamic mechanical thermal analysis, dynamic water vapor sorption, oxygen transmission and tensile tests. Property changes are interpreted from structural changes. These new polymers show much superior performance to current petroleum-based polymers in industrial use. Furthermore, this regioselective modification can be carefully controlled, and results in a new type of cellulose derivatives with preserved cellulose backbone without the need for harmful solvents.
- Published
- 2013
6. Focused ion beam irradiation: morphological and chemical evolution in epoxy polymers
- Author
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Wulff Possart, Flavio Soldera, Joby J. Kochumalayil, and A. Meiser
- Subjects
chemistry.chemical_classification ,Materials science ,Scanning electron microscope ,technology, industry, and agriculture ,Analytical chemistry ,food and beverages ,Surfaces and Interfaces ,General Chemistry ,Polymer ,Epoxy ,Condensed Matter Physics ,Focused ion beam ,Surfaces, Coatings and Films ,Scanning probe microscopy ,chemistry ,Etching ,Attenuated total reflection ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,Surface layer ,Composite material - Abstract
This work contributes to the understanding of focused ion beam (FIB) technology for polymers. The conditions of treatment are varied, in particular by etching under ‘dry’ ultra-high vacuum conditions or in the presence of water vapour. For a glassy epoxy network, the changes in chemistry and morphology are characterised. Energy-dispersive X-ray analysis reveals that gallium is always implanted in the epoxy but the content is higher in the case of ‘dry’ FIB milling. According to attenuated total reflection infrared micro-spectroscopy, new chemical structures form in the surface region of the epoxy during FIB milling with or without water vapour. Scanning electron microscopy and scanning force microscopy were used to image the topography of the etched epoxy surfaces. Quite smooth surfaces result under ‘dry’ etching conditions. In the presence of water vapour, rough surfaces with a sub-micrometre globular morphology are obtained. This is an indication of the heterogeneous morphology of the epoxy polymer. As compared to ‘dry’ conditions, the introduction of water vapour during FIB milling increases the milling yield significantly. As a result, the FIB treatment changes the chemistry and the structure of the epoxy network not only at the very surface but also in some significant surface layer of the sample. It can be expected that such a modified zone will also form on other cross-linked polymers. Copyright © 2009 John Wiley & Sons, Ltd.
- Published
- 2009
7. Focused ion beam irradiation-morphological and chemical evolution in PMMA
- Author
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Wulff Possart, Joby J. Kochumalayil, A. Meiser, and Flavio Soldera
- Subjects
Beam diameter ,Chemistry ,Scanning electron microscope ,Analytical chemistry ,Infrared spectroscopy ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Focused ion beam ,Surfaces, Coatings and Films ,Amorphous solid ,Ion ,Attenuated total reflection ,Materials Chemistry ,Ion milling machine - Abstract
For poly(methyl methacrylate) (PMMA) as a representative of amorphous thermoplastic polymers, the milling effects, and the chemical changes due to ion bombardment with a focused ion beam (FIB) at normal incidence are studied with scanning force microscopy (SFM), scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), and infrared (IR) spectroscopy for varying conditions of Ga+ treatment, including the effect of partial water pressure. Stopping and Range of Ions in Matter (SRIM) simulation results for 30 keV Ga+ at normal incidence show that the zone of primary ion–polymer interaction extends ca 100 nm into the PMMA. Accordingly, this interaction region is much wider than the original beam diameter. The width of the region where the recoiled ions interact strongly with the polymer chains is larger. Secondary processes, such as fragment diffusion and phonon transport, are expected to extend even farther into the polymer. SEM and SFM reveal distinct topologies of areas milled without or in presence of water vapour. Water vapour–assisted FIB milling produces more roughness and defects. The infrared attenuated total reflection spectroscopy (IR-ATR) spectra indicate that ion milling in PMMA damages methacrylate side groups in particular. In contrary to metals, an increase in the degree of milling is found when the beam spot overlap parameter increases. Copyright © 2009 John Wiley & Sons, Ltd.
- Published
- 2009
8. Oriented clay nanopaper from biobased components--mechanisms for superior fire protection properties
- Author
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Federico Carosio, Joby J. Kochumalayil, Giovanni Camino, Fabio Cuttica, and Lars Berglund
- Subjects
Paper ,Thermogravimetric analysis ,Materials science ,biocomposite ,Hot Temperature ,Poison control ,thermal stability ,Fires ,Nanocellulose ,Nanocomposites ,Materials Testing ,General Materials Science ,Thermal stability ,Composite material ,Particle Size ,Cellulose ,nanocellulose ,Flammability ,Flame Retardants ,brick and mortar ,Biological Products ,Nanocomposite ,nanocomposite ,fire protection ,layered silicate ,Thermal Conductivity ,Anisotropy ,Clay ,Aluminum Silicates ,Biocomposite ,Fire retardant - Abstract
The toxicity of the most efficient fire retardant additives is a major problem for polymeric materials. Cellulose nanofiber (CNF)/clay nanocomposites, with unique brick-and-mortar structure and prepared by simple filtration, are characterized from the morphological point of view by scanning electron microscopy and X-ray diffraction. These nanocomposites have superior fire protection properties to other clay nanocomposites and fiber composites. The corresponding mechanisms are evaluated in terms of flammability (reaction to a flame) and cone calorimetry (exposure to heat flux). These two tests provide a wide spectrum characterization of fire protection properties in CNF/montmorrilonite (MTM) materials. The morphology of the collected residues after flammability testing is investigated. In addition, thermal and thermo-oxidative stability are evaluated by thermogravimetric analyses performed in inert (nitrogen) and oxidative (air) atmospheres. Physical and chemical mechanisms are identified and related to the unique nanostructure and its low thermal conductivity, high gas barrier properties and CNF/MTM interactions for char formation.
- Published
- 2015
9. 'Brick-and-Mortar' Composites of Platelet-Reinforced Polymers
- Author
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Joby J. Kochumalayil and Lars A. Berglund
- Published
- 2015
10. Molecular adhesion at clay nanocomposite interfaces depends on counterion hydration-molecular dynamics simulation of montmorillonite/xyloglucan
- Author
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Joby J. Kochumalayil, Lars Berglund, Jakob Wohlert, Malin Bergenstråhle-Wohlert, Hans Ågren, Yaoquan Tu, and Yan Wang
- Subjects
inorganic chemicals ,Models, Molecular ,Polymers and Plastics ,Polymer nanocomposite ,Surface Properties ,Bioengineering ,Molecular Dynamics Simulation ,complex mixtures ,Divalent ,Nanocomposites ,Biomaterials ,Molecular dynamics ,chemistry.chemical_compound ,Adsorption ,Biopolymers ,Tensile Strength ,Polymer chemistry ,Materials Chemistry ,Glucans ,chemistry.chemical_classification ,Nanocomposite ,Chemistry ,Water ,Adhesion ,Montmorillonite ,Chemical engineering ,Bentonite ,Clay ,Aluminum Silicates ,Xylans ,Counterion - Abstract
Nacre-mimetic clay/polymer nanocomposites with clay platelet orientation parallel to the film surface show interesting gas barrier and mechanical properties. In moist conditions, interfacial adhesion is lowered and mechanical properties are reduced. Molecular dynamic simulations (MD) have been performed to investigate the effects of counterions on molecular adhesion at montmorillonite clay (Mnt)-xyloglucan (XG) interfaces. We focus on the role of monovalent cations K(+), Na(+), and Li(+) and the divalent cation Ca(2+) for mediating and stabilizing the Mnt/XG complex formation. The conformation of adsorbed XG is strongly influenced by the choice of counterion and so is the simulated work of adhesion. Free energy profiles that are used to estimate molecular adhesion show stronger interaction between XG and clay in the monovalent cation system than in divalent cation system, following a decreasing order of K-Mnt, Na-Mnt, Li-Mnt, and Ca-Mnt. The Mnt clay hydrates differently in the presence of different counterions, leading to a chemical potential of water that is highest in the case of K-Mnt, followed by Na-Mnt and Li-Mnt, and lowest in the case of Ca-Mnt. This means that water is most easily displaced from the interface in the case of K-Mnt, which contributes to the relatively high work of adhesion. In all systems, the penalty of replacing polymer with water at the interface gives a positive contribution to the work of adhesion of between 19 and 35%. Our work confirms the important role of counterions in mediating the adsorption of biopolymer XG to Mnt clays and predicts potassium or sodium as the best choice of counterions for a Mnt-based biocomposite design.
- Published
- 2014
11. Multifunctional nanoclay hybrids of high toughness, thermal, and barrier performances
- Author
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Houssine Sehaqui, Lars Berglund, Tanja Zimmermann, Joby J. Kochumalayil, and Andong Liu
- Subjects
chemistry.chemical_classification ,Toughness ,Materials science ,Dynamic mechanical analysis ,Polymer ,chemistry.chemical_compound ,Montmorillonite ,chemistry ,General Materials Science ,Dynamic vapor sorption ,Composite material ,Ductility ,Hydroxyethyl cellulose ,Tensile testing - Abstract
To address brittleness of nanoclay hybrids of high inorganic content, ductile polymers (polyethylene oxide and hydroxyethyl cellulose) and montmorillonite (MTM) have been assembled into hybrid films using a water-based filtration process. Nacre-mimetic layered films resulted and were characterized by FE-SEM and XRD. Mechanical properties at ambient condition were studied by tensile test, while performance at elevated temperature and moisture conditions were evaluated by TGA, dynamic vapor sorption, and dynamic thermomechanical and hygromechanical analyses. Antiflammability and barrier properties against oxygen and water vapor were also investigated. Despite their high MTM content in the 60-85 wt % range, the hybrids exhibit remarkable ductility and a storage modulus above 2 GPa even in severe conditions (300°C or 94% RH). Moreover, they present fire-shielding property and are amongst the best oxygen and water vapor barrier hybrids reported in the literature. This study thus demonstrates nanostructure property advantages for synergistic effects in hybrids combining inexpensive, available, and environmentally benign constituents.
- Published
- 2013
12. Toward an alternative compatibilizer for PLA/cellulose composites: grafting of xyloglucan with PLA
- Author
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Camilla Nilsson, Joby J. Kochumalayil, E. Kristofer Gamstedt, Andrew Marais, and Linda Fogelström
- Subjects
Polymers and Plastics ,Polymers ,Polyesters ,Organic Chemistry ,Substrate (chemistry) ,Grafting ,Ring-opening polymerization ,Xyloglucan ,chemistry.chemical_compound ,Monomer ,chemistry ,Polymerization ,Polylactic acid ,Polymer chemistry ,Materials Chemistry ,Xylans ,Lactic Acid ,Composite material ,Cellulose ,Glucans - Abstract
Poly(L-lactic acid) (PLLA) chains were grafted on xyloglucan substrates via ring-opening polymerization of the L-lactide monomer. Different parameters such as the nature of the substrate (native or modified xyloglucan) and the substrate/monomer ratios were varied in the synthesis to achieve different lengths of the grafted chains. A range of experimental techniques including infrared spectroscopy and nuclear magnetic resonance were used to characterize the final product. Thermal analysis showed that the glass transition temperature of xyloglucan was decreased from 252 °C to 216 °C following the grafting of PLLA. The grafting of less hydrophilic chains from xyloglucan also affected the interaction with water: the PLLA-grafted xyloglucan was insoluble in water and the moisture uptake could be decreased by about 30%. Xyloglucan adsorbs strongly to cellulose; therefore such a graft copolymer may improve the compatibility between cellulose fibers and PLLA. The PLLA-grafted xyloglucan may be useful as a novel compatibilizer in fiber-reinforced PLLA composites.
- Published
- 2012
13. Tamarind seed xyloglucan – a thermostable high-performance biopolymer from non-food feedstock
- Author
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Lars Berglund, Qi Zhou, Joby J. Kochumalayil, and Houssine Sehaqui
- Subjects
Materials science ,Moisture ,Starch ,Sorption ,General Chemistry ,engineering.material ,Raw material ,Xyloglucan ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Materials Chemistry ,Glycerol ,engineering ,Thermal stability ,Biopolymer ,Composite material - Abstract
Polysaccharide biopolymers from renewable resources are of great interest as replacements for petroleum-based polymers since they have lower cradle-to-grave non-renewable energy use and greenhouse gas emissions. Starch is widely used as a packaging material but is based on food resources such as potato or corn, and suffers from high sensitivity to water vapor even under ambient conditions. For the first time, xyloglucan (XG) from tamarind seed waste is explored as an alternative high-performance biopolymer from non-food feedstock. XG is purified, and dissolved in water to cast films. Moisture sorption isotherms, tensile tests and dynamic mechanical thermal analysis are performed. Glycerol plasticization toughening and enzymatic modification (partial removal of galactose in side chains of XG) are attempted as means of modification. XG films show much lower moisture sorption than the amylose component in starches. Stiffness and strength are very high, with considerable ductility and toughness. The thermal stability is exceptionally high and is approaching 250 °C. Glycerol plasticization is effective already at 10% glycerol. These observations point towards the potential of XG as a “new” biopolymer from renewable non-food plant resources for replacement of petroleum-based polymers.
- Published
- 2010
14. Nanostructurally Controlled Hydrogel Based on Small-Diameter Native Chitin Nanofibers: Preparation, Structure, and Properties.
- Author
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Mushi NE, Kochumalayil J, Cervin NT, Zhou Q, and Berglund LA
- Subjects
- Compressive Strength, Molecular Structure, Porosity, Chitin chemistry, Hydrogels chemistry, Nanofibers chemistry
- Abstract
Chitin nanofibers of unique structure and properties can be obtained from crustacean and fishery waste. These chitin nanofibers have roughly 4 nm diameters, aspect ratios between 25-250, a high degree of acetylation and preserved crystallinity, and can be potentially applied in hydrogels. Hydrogels with a chitin nanofiber content of 0.4, 0.6, 0.8, 1.0, 2.0, and 3.0 wt % were successfully prepared. The methodology for preparation is new, environmentally friendly, and simple as gelation is induced by neutralization of the charged colloidal mixture, inducing precipitation and secondary bond interaction between nanofibers. Pore structure and pore size distributions of corresponding aerogels are characterized using auto-porosimetry, revealing a substantial fraction of nanoscale pores. To the best of our knowledge, the values for storage (13 kPa at 3 wt %) and compression modulus (309 kPa at 2 wt %) are the highest reported for chitin nanofibers hydrogels., (© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)
- Published
- 2016
- Full Text
- View/download PDF
15. Multifunctional nanoclay hybrids of high toughness, thermal, and barrier performances.
- Author
-
Sehaqui H, Kochumalayil J, Liu A, Zimmermann T, and Berglund LA
- Abstract
To address brittleness of nanoclay hybrids of high inorganic content, ductile polymers (polyethylene oxide and hydroxyethyl cellulose) and montmorillonite (MTM) have been assembled into hybrid films using a water-based filtration process. Nacre-mimetic layered films resulted and were characterized by FE-SEM and XRD. Mechanical properties at ambient condition were studied by tensile test, while performance at elevated temperature and moisture conditions were evaluated by TGA, dynamic vapor sorption, and dynamic thermomechanical and hygromechanical analyses. Antiflammability and barrier properties against oxygen and water vapor were also investigated. Despite their high MTM content in the 60-85 wt % range, the hybrids exhibit remarkable ductility and a storage modulus above 2 GPa even in severe conditions (300°C or 94% RH). Moreover, they present fire-shielding property and are amongst the best oxygen and water vapor barrier hybrids reported in the literature. This study thus demonstrates nanostructure property advantages for synergistic effects in hybrids combining inexpensive, available, and environmentally benign constituents.
- Published
- 2013
- Full Text
- View/download PDF
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