8 results
Search Results
2. An anisotropic fibre-network model for mechano-sorptive creep in paper
- Author
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Strömbro, Jessica and Gudmundson, Peter
- Subjects
- *
WEATHER , *METEOROLOGY , *ATMOSPHERIC water vapor , *MOISTURE - Abstract
Abstract: In this paper a simplified network model for mechano-sorptive creep is presented, which is a further development of an earlier paper [Strömbro, J., Gudmundson, P., 2008. Mechano-sorptive creep under compressive loading – a micromechanical model. International Journal of Solids and Structures 45 (9), 2420–2450.]. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys a constitutive law that is non-linear. Fibre kinks are included in order to capture experimental observations of larger mechano-sorptive effects in compression than in tension. Moisture dependent material parameters and anisotropy in the fibre distribution have been introduced. Theoretical predictions based on the model are compared to experimental results for an anisotropic paper both under tensile and compressive loading at varying moisture content and it is found that the important features in the experiments are captured by the model. Different kinds of drying conditions have also been examined. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
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3. Mechano-sorptive creep under compressive loading – A micromechanical model
- Author
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Strömbro, Jessica and Gudmundson, Peter
- Subjects
- *
MOISTURE , *HUMIDITY , *MICROMECHANICS , *SOLID state physics - Abstract
Abstract: The creep of paper is accelerated by moisture cycling, an effect known as mechano-sorptive creep. It has also been observed that the mechano-sorptive effects are larger in compression than in tension. In this paper a simplified network model for mechano-sorptive creep is presented. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre–fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys constitutive laws that are non-linear in stress. Geometrical fibre effects are included in the model in order to capture experimental observations of the differences between paper loaded in tension and compression. Theoretical predictions based on the developed model are compared to experimental results for paper both under tensile and compressive loading at varying moisture content. The important features in the experiments are captured by the model, i.e. the creep is accelerated by the moisture cycling and the mechano-sorptive effects are larger in compression than in tension. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
4. The characterisation of paper-composite porcelain in a green state
- Author
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Jeoung-Ah, Kim
- Subjects
- *
PORCELAIN , *COMPOSITE materials , *CERAMICS , *SCANNING electron microscopy , *ELECTRON microscopy - Abstract
Abstract: A porcelain body traditionally used to produce ceramic art and design objects was re-formulated using additional waste paper. The aim of this study was to develop knowledge into the technological properties of paper-composite porcelain in its green state, for use within the traditional practices of ceramic art and design production. Characterisation was made by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Two different production methods used by potters, slip casting and free-hand pressing, were used. The presence of the paper fibre, the paper type and the content amount are the important factors in strengthening development. Significant differences were found in relation to the content amount of paper fibre, between the mother porcelain body and the different content amount of paper fibre in the paper-composite porcelain body. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
5. Conducting Polymers on Paper Fibres
- Author
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Johnston, James H, Moraes, John, and Borrmann, Thomas
- Subjects
- *
POLYMERS , *MACROMOLECULES , *COMPOSITE materials , *GLUCANS - Abstract
Abstract: Conducting polymers have generated a great deal of interest because of their physical and chemical properties as well as their potential in industrially useful materials. However, one of the shortcomings of most conducting polymers is that they are often formed as intractable films that are difficult to process [1]. To overcome this problem we have incorporated various conducting polymers into sheets of paper in order to create new composite materials which combine the universal properties of a paper sheet or paper products with the chemical and electrically conducting properties of the conducting polymer. Various composite paper – conducting polymer products have been prepared by polymerizing polypyrrole and polyaniline directly onto the paper sheet using ferric chloride as the oxidant. Electronmicroscopy shows that the polymers comprise spheres of about 50–150 nanometers in size fused together such that they fully encapsulate the individual cellulose fibres in the paper sheet. The open matrix of fibres characteristic of the original paper sheet is maintained and hence provides a much greater specific surface area for the conducting polymer than that of a continuous flat sheet which would be the case if the polymer simply formed a laminar coating on the paper surface. In the case of polyaniline, it was also possible to form a different morphology of the polymer comprising a mix of nano-size spheres, rods and plates using ammonium persulfate as the oxidant. Conductivities of up to 6 Scm−1 have been measured for paper-polypyrrole composites and up to 2x10−3 Scm−1 for paper-polyaniline composites. [Copyright &y& Elsevier]
- Published
- 2005
- Full Text
- View/download PDF
6. Formability of paper and its improvement
- Subjects
fibres ,extensibility ,formability ,paper ,packaging ,3D forming ,compaction ,SDG 7 - Affordable and Clean Energy ,bonding - Abstract
Paper and paperboard are the most utilized packaging materials in the world. This position has been achieved due to several advantageous features of paper such as: renewability, biodegradability, recyclability, and unmatched printability. Paper can be produced anywhere in the world, using local resources and at relatively low cost, which also makes it the most sustainable packaging material. Despite these beneficial features, paper packaging is in tough competition with plastic materials. The competitiveness of paper is mitigated by barrier properties, sensitivity to moisture, and limited ability to be converted into advanced 3D shapes with added functionality. The ability of paper and paperboard to be formed into 3D shapes is described as formability, or sometimes, mouldability. Formability can be defined as the ability of paper to be formed into 3D shapes without defects in appearance and functionality. Formability as a mechanical property represents a group of parameters which vary according to the type of forming process used. The primary objective of this thesis is to improve the formability of paper by increasing its extensibility. An additional objective is the characterization of formability as a mechanical property of paper and the development of a testing platform for the evaluation of formability. It was found that the formability of paper in fixed blank forming processes is governed by the extensibility and tensile strength of paper. On the other hand, in sliding blank forming processes, it is dependent on the compressive properties of paper, elastic recovery, and the paper-to-metal coefficient of friction. The criteria of good formability are also different in these two cases, as fixed blank process formability is evaluated via the maximum depth of the shape, i.e. the deeper the shape, the better the formability. In the sliding blank process, formability is evaluated via the visual appearance of the shapes, i.e. the shapes with less profound compressive wrinkles and defects reflect good formability of paper. These results were established by comprehensive investigation of different forming processes and comparison of the outcome with the mechanical properties of paper. Taking into account the hypothesis that the formability of paper is governed by the extensibility of paper, a set of methods for its improvement was suggested. These methods included combined high- and low-consistency treatment of fibres, spraying of agar and gelatine, in-plane compaction of paper and unrestrained drying. High-consistency treatment of fibres under elevated temperature induces permanent deformations to fibres such as microcompressions and dislocations, which in turn may decrease the axial stiffness of fibres, promoting shrinkage of paper and fibres. The low-consistency treatment straightens the fibres and induces the fibrillation of fibres to promote bonding, while microcompressions in fibres still exist. The spraying of agar and gelatine is likely to modify the character of the fibre joints by making them more deformable, and the drying shrinkage is also increased due to polymer addition. Finally, the fibre network was subjected to in-plane compaction and drying shrinkage which lead to buckling and fibre and network compression. As a result of these treatments, the extensibility of unrestrained dried paper was increased from 4% points (untreated fibres) to 15-18% points (mechanical treatment and addition of polymers). The extensibility can be increased further by up to 30% points in one direction by compaction. This corresponds to tray-like shapes with a depth of 2-3 cm, depending on the curvature. Such values of formability are the highest reported so far in the scientific literature. The approach for the production of formable paper developed in this thesis work allows the production of a paper-based material with unmatched formability, which can replace certain types of plastic packaging. Replacement of plastics with paper improves the sustainability of packaging in general, and reduces the harmful environmental impact of non-degradable and non-renewable packaging.
- Published
- 2015
7. Formability of paper and its improvement
- Subjects
fibres ,extensibility ,formability ,paper ,packaging ,3D forming ,compaction ,ta216 ,bonding - Published
- 2015
8. Rapid functionalisation of cellulose-based materials using a mixture containing laccase activated lauryl gallate and sulfonated lignin
- Author
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Cristina Valls, M. Blanca Roncero, Oriol Cusola, Teresa Vidal, Universitat Politècnica de Catalunya. Departament d'Enginyeria Tèxtil i Paperera, and Universitat Politècnica de Catalunya. CELBIOTECH - Grup de Recerca: Enginyeria Paperera
- Subjects
Paper ,Materials science ,Sonication ,dispersants ,Dispersant ,Biomaterials ,Contact angle ,chemistry.chemical_compound ,functionalisation ,Enginyeria paperera::Primeres matèries papereres::Cel·lulosa [Àrees temàtiques de la UPC] ,Lignin ,Organic chemistry ,Lignosulfonates ,Cellulose ,hydrophobicity ,Laccase ,Lignocel·lulosa ,Fibres ,lignosulfonates ,Surface energy ,cellulose ,Fibers ,chemistry ,Chemical engineering ,Cel·lulosa per a paper ,laccase treatment - Abstract
An innovative method has been developed for the surface hydrophobisation of cellulose-based materials by coating it with a functionalised solution (FS), in which sonicated lauryl gallate (LG, dodecyl 3,4,5,-trihydroxybenzoate), sulfonated kraft lignin, and the enzyme laccase play a pivotal role. The rapid treatment with FS increases the hydrophobicity of cellulose sheets considerably. The FS retention on the paper surface was analysed as a function of refining and application of additives. The properties of the functionalised sheets were assessed by the water-drop test (WDT), and the surface free energy (SFE) was determined via contact angle (CA) measurements in a goniophotometer. WDT resulted in long absorption times of up to 4000 s and CA values were around 130°. Functionalised solution modification of eucalyptus paper sheets decreased SFE essentially from 55 mJ m-2 to 10 mJ m-2. ATR-FTIR suggested that FS was grafted onto the cellulosic sheets. The stability of FS and the control solutions were characterised by Z potential and light scattering measurements. The functionalised solution method is a one-step roll-to-roll process, which is easy to perform also in industrial application without additional investments. It has a potential to substitute the traditional hydrophobing processes.
- Published
- 2014
- Full Text
- View/download PDF
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