Gary Chinga Carrasco - Academia.edu (original) (raw)

Papers by Gary Chinga Carrasco

Wear, 2013

Paper can be coated with liquid flame spray (LFS) generated nanoparticles to control the wettabil... more Paper can be coated with liquid flame spray (LFS) generated nanoparticles to control the wettability of its surface from hydrophilic to superhydrophobic. The adhesion of the nanoparticles on paper is of interest both for understanding the product durability during its lifetime and for product safety issues. Poor particle adhesion influences the desired functional properties and released nanoparticles cause health and environmental concerns. To investigate the wear resistance of LFS-TiO 2 and -SiO 2 coated papers, the nanoparticle surfaces were exposed to rotary abrasion tests. The changes in the samples were analyzed by contact angle measurements and high resolution field-emission scanning electron microscopy (FESEM). After abrasive action with another paperboard surface, only relatively small changes in wettability of superhydrophobic/hydrophilic coatings were found. A more severe abrasive action will remove some of the nanoparticle coating, but the hydrophobic/hydrophilic character of the surface is still maintained to large extent. The results indicate that the wear resistance of LFS nanocoated paper surfaces differs and depends on the nanoparticle material type used for the coating. This is clearly reflected as changes in surface structure shown by FE-SEM and wettability. The results can help understanding which paper-related application areas could be targeted with the LFS-nanoparticle coating process.

Micron, 2009

A shape description approach is introduced as a step for performing an automatic processing of fi... more A shape description approach is introduced as a step for performing an automatic processing of fibre cross-sectional images. The approach, in combination with appropriate mathematical morphology, yields edited images, which are suitable for further computerized image analysis. Important parameters such as fibre wall thickness, fibre perimeter, form factor and collapse index are quantified effectively and objectively. Although some differences are encountered within groups of split fibres, manual and automatic quantification of intact fibres yields similar results. In addition, the suitability of a distance transform approach for quantifying the fibre inter-distances in composites is demonstrated. Such tools will be valuable for understanding the mechanical properties of engineered fibre-reinforced composite materials.

Micron, 2010

Please cite this article in press as: Chinga-Carrasco, G., et al., Structural quantification of w... more Please cite this article in press as: Chinga-Carrasco, G., et al., Structural quantification of wood fibre surfaces-Morphological effects of pulping and enzymatic treatment. Micron (2010), a b s t r a c t Wood fibres have been utilized by our society as an important component of paper products and are presently gaining more interest as reinforcement in composite materials. During the last decades biochemical treatments have also found applications in the processing of wood fibres. The chemical, mechanical and biochemical treatments affect the morphology of the fibre wall structure at the microand nano-level. In this study, we present a modern approach where field-emission SEM (FE-SEM) and relevant computerized image analysis are applied to quantify the fibre wall characteristics. Details such as surface roughness and texture of the fibre walls are quantified objectively. Global polar plots are generated, which are considered to represent the fingerprint of a given pulp. The approach offers a novel perspective in the characterisation of surface structures, moving forward from performing subjective evaluations to performing objective quantifications of wood pulp fibre surfaces. Please cite this article in press as: Chinga-Carrasco, G., et al., Structural quantification of wood fibre surfaces-Morphological effects of pulping and enzymatic treatment. Micron (2010), Please cite this article in press as: Chinga-Carrasco, G., et al., Structural quantification of wood fibre surfaces-Morphological effects of pulping and enzymatic treatment. Micron (2010),

Journal of Colloid and Interface Science, 2011

The nature of layers formed by cellulose nanofibrils that had been surface modified (hydrophobize... more The nature of layers formed by cellulose nanofibrils that had been surface modified (hydrophobized) at the oil/water (o/w) interface was investigated. The aim of the study was to clarify the mechanism underlying the excellent ability of these nanoparticles to stabilize emulsions. Layers of hydrophobized nanofibrillated cellulose spread at the o/w interface were deposited on glass slides by the Langmuir-Blodgett deposition technique. Overall evaluation of layer structures was performed by image analysis based on a Quadtree decomposition of images obtained from a flatbed scanner. A more detailed characterization of the layer structures was performed by Atomic Force Microscopy (AFM), and Field-Emission Scanning Electron Microscopy (FE-SEM). The results show that nanofibrils that were able to stabilize emulsions occur as single, dispersed fibrils or form large, network-like aggregates at the o/w interface. Fibrils that were insufficiently hydrophobized and therefore did not stabilize emulsions were only partially deposited and formed small, compact aggregates. We conclude that it is likely that the network formation is the main mechanism by which the fibrils prevent coalescence of emulsion droplets.

Journal of Nanoparticle Research, 2011

Films made of nanofibrils were modified by adsorption of a cationic surfactant directly on the fi... more Films made of nanofibrils were modified by adsorption of a cationic surfactant directly on the film surfaces. The nanofibrils were prepared by 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation and mechanical fibrillation, and were relatively homogeneous in size. The average nanofibril diameter and surface porosity was quantified based on computer-assisted field-emission scanning electron microscopy (FE-SEM). The cationic surfactant used in the adsorption was n-hexadecyl trimethylammonium bromide (cetyltrimethylammonium bromide, CTAB). The adsorption of CTAB was confirmed by Fourier transform infrared (FTIR) spectroscopy and high-resolution transmission electron microscopy (HRTEM) analyses. It was shown that the adsorbed layer of CTAB increased the hydrophobicity, without affecting the tensile index significantly. This capability, combined with the antiseptic properties of CTAB, may be a major advantage for several applications.

This work presents a comparison of two statistical approaches for automatic classification of fib... more This work presents a comparison of two statistical approaches for automatic classification of fibre shapes, i.e. Canonical Discriminant Analysis (CDA) and Mahalanobis Discriminant Analysis (MLDA). The discriminant analyses were applied to identify and classify several fibre cross-sectional shapes, including e.g. intact, collapsed, touching and fibrillated fibres. The discriminant analyses perform differently, giving clear indications of their suitability for classifying a given group of fibre elements. Compared to CDA, MLDA was more reliable and relatively stable.

Procedia Engineering, 2010

In this paper, the double layer concept of knitted fabrics suitable for performance sportswear, w... more In this paper, the double layer concept of knitted fabrics suitable for performance sportswear, where each layer is separate from the other, was studied. Aerodynamic properties of this assembly, where the base layer is made of 100% wool and an external layer made of 100% filament polyester were determined. Fabric samples were placed over a single diameter cylinder to imitate the human leg. The aerodynamic resistance was acquired at different speeds relevant to high speed winter sports. Evaluation of comfort properties (liquid moisture transport in multi-dimensions) of each layer as well as a double layer was performed and the liquid moisture management capacity of the assembly was classified.

Journal of Microscopy-oxford, 2009

Printing paper is an important communication and information medium affecting our daily activitie... more Printing paper is an important communication and information medium affecting our daily activities in several ways. The structure of paper may affect its optical, mechanical, fluid transport and print properties. In order to achieve a complete understanding of these processes a comprehensive characterization of relevant surface and bulk structures of paper is necessary. The paper grades considered in this study are newsprints, super calendered and coated papers. A detailed description of several image acquisition techniques used to assess the printing paper structures is given, including desktop scanners, profilometry, light microscopy, confocal laser scanning microscopy, scanning electron microscopy, atomic force microscopy, focused-ion-beam, X-ray microtomography and transmission electron microscopy. The presented methods cover a wide range of structure sizes, from the macro- to the sub-nano level. The complementary capabilities of the image acquisition techniques for assessing structural details of paper and prints are discussed.

Carbohydrate Polymers, 2011

This work comprises a comparison between Eucalyptus and Pinus radiata pulp fibres, as raw materia... more This work comprises a comparison between Eucalyptus and Pinus radiata pulp fibres, as raw materials for producing nanofibrils. The cellulose nanofibrils were produced mechanically and chemi-mechanically. Series of the fibres were subjected to a TEMPO mediated oxidation ...

Journal of Materials Science

Due to the typical large variability in the measured mechanical properties of flax fibres, they a... more Due to the typical large variability in the measured mechanical properties of flax fibres, they are often employed only in low grade composite applications. The present study aims to investigate the reasons for the variability in tensile properties of flax fibres. It is found that an inaccuracy in the determination of the cross-sectional area of the fibres is one major reason for the variability in properties. By applying a typical circular fibre area assumption, a considerable error is introduced into the calculated mechanical properties. Experimental data, together with a simple analytical model, are presented to show that the error is increased when the aspect ratio of the fibre cross-sectional shape is increased. A variability in properties due to the flax fibres themselves is found to originate from the distribution of defects along the fibres. Two distinctive types of stress–strain behaviours (linear and nonlinear) of the fibres are found to be correlated with the amount of defects. The linear stress–strain curves tend to show a higher tensile strength, a higher Young’s modulus, and a lower strain to failure than the nonlinear curves. Finally, the fibres are found to fracture by a complex microscale failure mechanism. Large fracture zones are governed by both surface and internal defects; and these cause cracks to propagate in the transverse and longitudinal directions.

Journal of Nanoparticle Research, 2010

Films made of nanofibrillated cellulose (NFC) are most interesting for use in packaging applicati... more Films made of nanofibrillated cellulose (NFC) are most interesting for use in packaging applications. However, in order to understand the film-forming capabilities of NFC and their properties, new advanced methods for characterizing the different scales of the structures are necessary. In this study, we perform a comprehensive characterisation of NFC-films, based on desktop scanner analysis, scanning electron microscopy in backscatter electron imaging mode (SEM-BEI), laser profilometry (LP) and field-emission scanning electron microscopy in secondary electron imaging mode (FE-SEM-SEI). Objective quantification is performed for assessing the (i) film thicknesses, (ii) fibril diameters and (iii) fibril orientations, based on computer-assisted electron microscopy. The most frequent fibril diameter is 20–30 nm in diameter. A method for acquiring FE-SEM images of NFC surfaces without a conductive metallic layer is introduced. Having appropriate characterisation tools, the structural and mechanical properties of the films upon moisture were quantified.

Microscopy and Microanalysis, 2011

This work comprises the structural characterization of Eucalyptus and Pinus radiata pulp fibers a... more This work comprises the structural characterization of Eucalyptus and Pinus radiata pulp fibers and their corresponding fibrillated materials, based on quantitative electron microscopy techniques. Compared to hardwood fibers, the softwood fibers have a relatively open structure of the fiber wall outer layers. The fibrillation of the fibers was performed mechanically and chemi-mechanically. In the chemi-mechanical process, the pulp fibers were subjected to a TEMPO-mediated oxidation to facilitate the homogenization. Films were made of the fibrillated materials to evaluate some structural properties. The thicknesses and roughnesses of the films were evaluated with standardized methods and with scanning electron microscopy (SEM), in backscattered electron imaging mode. Field-emission SEM (FE-SEM) and transmission electron microscopy (TEM) were performed to quantify the nanofibril morphology. In this study, we give additional and significant evidences about the suitability of electron microscopy techniques for quantification of nanofibril structures. In addition, we conclude that standard methods are not suitable for estimating the thickness of films having relatively rough surfaces. The results revealed significant differences with respect to the morphology of the fibrillated material. The differences are due to the starting raw material and to the procedure applied for the fibrillation.

Cellulose, 2009

A new concept for both furnish composition and z-directional furnish arrangement involving the in... more A new concept for both furnish composition and z-directional furnish arrangement involving the interaction between specific thermo-mechanical pulp fractions (TMP), nanofibrillated cellulose (NFC) and clay in oriented layered laboratory sheets is presented. Used separately, NFC improves the strength properties of paper while fillers enhance the optical properties. Synergy effects of clay–NFC interactions are assessed. The study comprises a structural assessment, including laser profilometry, scanning electron microscopy (SEM) and field-emission (FE)-SEM analyses. In addition, optical and strength properties are assessed. It is demonstrated that a potential reduction of strength properties caused by filler addition may be counteracted by appropriate NFC addition to specific layers in the z-direction. Based on an estimation of an overall quality index considering five variables, it is concluded that the best sheet construction is obtained when placing the fillers in surface layers with the TMP accept fraction and the NFC in the centre of the sheets together with the refined TMP reject fraction.

During the last decade, major efforts have been made to develop adequate and commercially viable ... more During the last decade, major efforts have been made to develop adequate and commercially viable processes for disintegrating cellulose fibres into their structural components. Homogenisation of cellulose fibres has been one of the principal applied procedures. Homogenisation has produced materials which may be inhomogeneous, containing fibres, fibres fragments, fibrillar fines and nanofibrils. The material has been denominated microfibrillated cellulose (MFC). In addition, terms relating to the nano-scale have been given to the MFC material. Several modern and high-tech nano-applications have been envisaged for MFC. However, is MFC a nano-structure? It is concluded that MFC materials may be composed of (1) nanofibrils, (2) fibrillar fines, (3) fibre fragments and (4) fibres. This implies that MFC is not necessarily synonymous with nanofibrils, microfibrils or any other cellulose nano-structure. However, properly produced MFC materials contain nano-structures as a main component, i.e. nanofibrils.