| 1. |
- Kugge, C, et al.
(författare)
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A scanning electron microscope study of the surface structure of model paper coatings
- 2004
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Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 238, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the structure of model paper coating layers, composed of mineral pigments, latex binders and polymeric thickeners and dispersants, using Scanning Electron Microscopy (SEM). The main aim of the study is to identify how systematic variations in the composition of the coating, including pigment type (calcium carbonate, clay), the glass transition temperature of the binder, type (CMC, EHEC) and molecular weight of the polymeric thickener affect the surface features of the coating layer, including surface roughness and porosity and, consequently, gloss. The samples are investigated mainly in conventional high-vacuum SEM mode; however some studies are also performed with the environmental feature (ESEM mode) at higher pressures and humidities, in order to track dynamic changes drying and rewetting. The results are compared to those of recent measurements on the same systems obtained with Atomic Force Microscopy (AFM), where the local latex film formation process has been carefully studied
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| 2. |
- Kugge, C
(författare)
-
An AFM study of local film formation of latex in paper coatings
- 2004
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 30, s. 105-111
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Tidskriftsartikel (refereegranskat)abstract
- The local film formation of latex in model paper coating suspensions of low latex to CaCO3 volume fraction ratio, 0.27, has been studied using both topographic and phase images of atomic force microscopy. Local film formation is believed to work concurrently with latex migration. Both the dosage and molecular weight of carboxymethylcellulose (CMC) have a visible effect on latex film formation. A greater dosage of CMC retards latex migration and a higher molecular weight of CMC prolongs the film-formation process. Another thickener, ethyl(hydmxyethyl)cellulose (EHEC), was compared to CMC, and EHEC creates a composite where deformed latex particles are encapsulated in EHEC. A higher Tg latex increases the amount of latex in the upper region of the coating. It is suggested that a lower Tg latex halts migration, which leads to film formation at an earlier stage, further down in an evaporating pore
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| 3. |
- Kugge, C, et al.
(författare)
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Compressional rheology of model paper coatings
- 2001
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Ingår i: The Science of Papermaking. - Lancashire : FRC, Pulp & Paper Fundamental Research Society. ; , s. 1183-1202
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Bokkapitel (refereegranskat)abstract
- The surface treatment of paper is commonly undertaken in order to improve a set of key end-use properties, including optical response and printability. These properties can be influenced, to a significant extent, by the sub-surface structure of the coating layer. The nature of coating dewatering also has strong implications for machine runnability. Thus, there is a clear need to understand in suitable detail the nature of the coating consolidation process. In this study, we have applied a novel approach to characterising the equilibrium consolidation state of calcium carbonate sediments, both with and without polymeric thickener. The aim is to provide a quantitative link between the structure of consolidated layers and their network strength, though the compressive yield stress. A suspension, prepared at a given volume fraction of solid, is centrifuged to produce a consolidated particle sediment (or gel). The solidity variation of that sediment as a function of depth is then measured using one-dimensional magnetic resonance imaging (MRI), and the compressive yield stress calculated directly from the volume fraction profile. The results obtained are discussed in the light of particle network structure, the effect of polymer on particle consolidation, and the relation to viscoelastic properties of the suspensions. The link to the dewatering of coating suspensions, and structure formation in coating layers, is also considered.
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| 4. |
- Kugge, C, et al.
(författare)
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Pressure filtration of cellulose fibres
- 2005
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 31, s. 95-100
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Tidskriftsartikel (refereegranskat)abstract
- The compressional rheology of cellulose fibre suspensions has been studied using a pressure filtration technique. The dewatering of these systems is thus described in terms of various key properties of the suspension, including the compressive yield stress, permeability and solids diffusivity, permitting a quantitative characterisation of the consolidation process. We investigate as a particular example the effect of a commercial debonding agent additive on the compressional properties of a fibre suspension. Such agents are commonly used in the production of hygiene products where they are added to decrease the strength of fibre-fibre bonds. Here we investigate their effect on the compressive response of fibre suspensions as an example of how measurements of this type can be used to characterise the effect of additives on bulk properties. The results indicate that addition of debonder causes a somewhat higher dewatering tendency as the solids level is increased.
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| 5. |
- Kugge, C, et al.
(författare)
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Shear response of concentrated calcium carbonate suspensions
- 2004
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 271, s. 241-248
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Tidskriftsartikel (refereegranskat)abstract
- The rheology of concentrated calcium carbonate suspensions is investigated with respect to addition of solution and dispersion polymers. System materials and composition are chosen to be similar, generically, to those in use in the coating of paper. Specifically, we investigate the particle volume fraction dependence of the relative viscosity, using both capillary and steady-shear concentric cylinder measurement methods to cover a broad range of concentrations. The results are interpreted in terms of semi-empirical models, such as the Krieger–Dougherty model. Oscillatory shear measurements are also employed to investigate the viscoelastic behavior of the concentrated suspensions. The measurements indicate that a common solution polymer thickener, carboxymethyl cellulose (CMC), causes depletion flocculation of calcium carbonate suspensions.
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