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Wood pulp fibres are an important component of environmentally sound and renewable fibre-reinforced composite materials. The high aspect ratio of pulp fibres is an essential property with respect to the mechanical properties a given composite material can achieve. The length of pulp fibres is affected by composite processing operations. This thus emphasizes the importance of assessing the pulp fibre length and how this may be affected by a given process for manufacturing composites. In this work a new method for measuring the length distribution of fibres and fibre fragments has been developed. The method is based on; (i) dissolving the composites, (ii) preparing the fibres for image acquisition and (iii) image analysis of the resulting fibre structures. The image analysis part is relatively simple to implement and is based on images acquired with a desktop scanner and a new ImageJ plugin. The quantification of fibre length has demonstrated the fibre shortening effect because of an extrusion process and subsequent injection moulding. Fibres with original lengths of >1 mm where shortened to fibre fragments with length of <200 μm. The shortening seems to be affected by the number of times the fibres have passed through the extruder, the amount of chain extender and the fraction of fibres in the polymer matrix. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We present preliminary theoretical-experimental results in the crystalline growth of Fe(OH) 3 and CuS inorganic nanomaterials. These were obtained employing the Chemical Bath Deposition technique and thermally annealing treated at ~ 1000 °C in the air atmosphere. In each case, the proposed chemical kinetic model supports the obtained complex coordination [Fe(NH 3) 6 ]3+ and [Cu(NH 3) 4 ]2+ ions and then serves to investigate theoretical-experimental insights of the Fe(OH) 3 and CuS products. Scanning Electron Microscopy (SEM) images show spongy crystals in Fe(OH) 3(s) and CuS (s) that drastically change to dense plates in both inorganic materials due to thermal annealing treatment. The X-ray diffraction (XRD) studies identify Fe(OH) 3 →α-Fe 2 O 3(s) phase transition to oxide (Rhombo.H.axes). Differential Scanning Calorimetric (DSC) studies show the loss of mass and the gradual transition of Fe(OH) 3 →α-Fe 2 O 3(s). Likewise, the CuS (s) (Orthorhombic S 8 cyclo-octasulfur) is identified. It is possibly interlaced and forming -S-Cu-S- chemical bonds, with small nanoparticles of CuS (s) trapped within the (zig-zag) cyclical chains of the S 8. The GS ranges between ~ 23.2 and 27.8 nm for CuS 8(s) and ~ 35.5 and 38.8 for CuO (s). [ABSTRACT FROM AUTHOR]

Cellulose nanofibrils (CNF) were isolated from agro-industrial waste (corn husks and oat hulls) and market kraft pulp fibres, and a detailed comparative study was performed. Initially, the raw materials were subjected to a conventional pulping process to remove lignin and hemicelluloses. The chemical pre-treatment was based on 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation and the mechanical treatment was carried out with a high-pressure homogenizer. An extensive characterization of the raw material and of the nanofibrillated celluloses was performed, considering structural and chemical aspects. CNF films were produced for their characterization by optical methods, laser profilometry (LP), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Considering the same pulping and chemical pre-treatment, the analyses indicated that the oxidized corn husks fibres had higher carboxylate content and thus a larger tendency to nanofibrillate compared to the oat hulls fibres. The obtained content of carboxylic acids was directly proportional to the content of cellulose in the assessed samples, confirming the selectivity of the TEMPO-mediated oxidation. The fibrillated corn husks material had a minor fraction of residual fibres (<4%) and homogeneous nanofibril width distribution (<20 nm), which is a major achievement. The homogeneous CNF morphology was confirmed by AFM analysis. Hence, this study demonstrates that the assessed agro-industrial wastes are sustainable resources for production of CNF, which may have a wide range of value-added applications. [ABSTRACT FROM AUTHOR]