One severe weakness of most biopolymers, in terms of their use as packaging materials, is their relatively high solubility in water. The addition of kraft lignin to starch coating formulations has been shown to reduce the water solubility of starch in dry coatings. However, lignin may also migrate into aqueous solutions. For this paper, kraft lignin isolated using the LignoBoost process was used in order to examine the effect of pH level on the solubility of lignin with and without ammonium zirconium carbonate (AZC). Machine-glazed (MG) paper was coated in a pilot coating machine, with the moving substrate at high speed, and laboratory-coated samples were used as a reference when measuring defects (number of pinholes). Kraft lignin became soluble in water at lower pH levels when starch was added to the solution, due to the interactions between starch and lignin. This made it possible to lower the pH of the coating solutions, resulting in increased water stability of the dry samples; that is, the migration of lignin to the model liquids decreased when the pH of the coating solutions was reduced. No significant difference was observed in the water vapor transmission rate (WVTR) between high and low pH for the pilot-coated samples. The addition of AZC to the formulation reduced the migration of lignin from the coatings to the model liquids and led to an increase in the water contact angle, but also increased the number of pinholes in the pilot-coated samples.

Dewatering and air flow in high vacuum suction boxes was examined. The work was mainly numerical and was based on, and compared with, previously published experimental results of vacuum dewatering from laboratory equipment and from a pilot paper machine. A previously published numerical model for wet pressing is used as the basis for this work. The aims of this study were to find new fitting parameters that allows the previous model to be used for vacuum dewatering instead of pressing, and to examine two extensions to the original model. The results indicate that the new vacuum dewatering model for moisture can predict the dewatering behavior for several different experimental data series both from laboratory equipment and a pilot paper machine using the same set of fitting parameters. Two different numerical models for air flow through the paper sheet, during vacuum dewatering, were developed based on postulating that the decrease in moisture permeability is accompanied by a simultaneous increase in air permeability. The models for air flow can also be fitted to experimental data and predict the magnitudes of air flow during vacuum dewatering. The data sets for air flow exhibit a certain degree of operator dependence though, so that one set of fitting parameters is not enough for obtaining good agreement with all data sets.

The addition of nano-and micro-fibrillated cellulose to conventional softwood Kraft pulps can enhance the product performance by increasing the strength properties and enabling the use of less raw material for a given product performance. However, dewatering is a major problem when implementing these materials to conventional paper grades because of their high water retention capacity. This study investigated how vacuum dewatering is affected by different types of additives. The hypothesis was that different types of pulp additions behave differently during a process like vacuum suction, even when the different additions have the same water retention value. One reference pulp and three additives were used in a laboratory-scaled experimental study of high vacuum suction box dewatering. The results suggested that there was a linear relationship between the water retention value and how much water that could be removed with vacuum dewatering. However, the linear relationship was dependent upon the pulp type and the additives. Additions of micro-fibrillated cellulose and dialcohol cellulose to the stock led to dewatering behaviors that suggested their addition in existing full-scale production plants can be accomplished without a major redesign of the wire or high vacuum section.

Barrier coatings based on starch and starch-PVOH plasticized with glycerol and without plasticizer were applied to two different paperboard substrates, a triple coated board and duplex board, in order to investigate the tendency for cracks to develop in the barrier coating layers during creasing and folding. Tensile properties of films based on the starch and starch-PVOH blend were determined to investigate the relationship between the flexibility of the films and the cracking in the barrier coating layers. Furthermore, the oxygen transmission rate through the barrier-coated paperboard was measured before and after creasing and folding. The oxygen transmission rate through the barrier-coated samples was over the measurable range i. e. OTR>10000cm³/m²day after creasing and folding, which indicated failure in the barrier coating layers. Optical microscopy revealed small cracks in the barrier coating layers, probably related to an increase in flexibility of the barrier coating layers. It was observed in scanning electron micrographs that cracks in the barrier coating layers seemed to follow the fibers when the barrier coating was applied on the rear side of the duplex board. Scanning electron micrographs and surface profiler images revealed that cracks in the barrier coating layers might have originated from the mineral coating layer when the starch and starch/PVOH coating layers were applied on the mineral-coated side of the triple coated board. An increase in the thickness of the barrier coating layer did not seem to increase the resistance to failure.

The mechanical properties and chemical stability in water of self-supporting films made from aqueous solutions of starch and lignin, and the barrier properties of paperboard coated with solutions of these polymers have been studied. The dissolution of starch from the starch-lignin films in contact with the model liquids was decreased significantly when lignin was added to the starch films. The addition of ammonium zirconium carbonate (AZC) to the formulations as a crosslinking agent substantially increased the storage modulus of the starch-lignin films, which indicated that crosslinking had occurred. The addition of AZC to the formulations also led to a decrease in dissolution of both starch and lignin from the starch-lignin films in contact with model liquids. The effect of AZC on the water stability of the films was greater when the pH of the starch-lignin-AZC solution was adjusted with ammonia rather than NaOH. The addition of NH4Cl solution as a presumed catalyst to the recipe when the pH adjustment was performed with NaOH did not improve the effect of AZC on the water stability of the films. The water vapour transmission rate of the coated paperboard decreased slightly when AZC was added to the coating formulation.

An ecofriendly approach for the synthesis of plastic biomaterials based on renewable materials suitable for 3D printing application or other applications has been developed. The material was prepared from native (microcrystalline) or amorphous cellulose, citric acid, and glycerol or ethylene glycol, by a pretreatment at 40 degrees C and a curing at 175 degrees C for 1 h. The results showed that tensile properties and the water absorption level of the material were acceptable. The highest strain at break (14%) was obtained from materials made of 10% amorphous cellulose with 90% glycerol/citric acid. It had a maximum stress at 37 MPa. Moreover, materials were without ash content. Possible applications of the material in 3D-printers were discussed. In addition, application of mechanical pulp and wood powder into novel plastic material production was discussed. Foaming during curing might be a problem for this type of material, but this can be avoided by using amorphous cellulose in the recipe.

Hypothesis: The sol-gel transition in aqueous suspensions consisting of silica particles and thermosensitive polymer is controlled by inter-particle forces and solution properties of the polymer. Addition of a second non-thermosensitive polymer may affect the transition. The purpose of this work was to characterize the kinetics of the sol-gel transition and to understand the effects of a second non-thermosensitive polymer on the microstructure, using a combination of classical rheology and microrheology. Experiments: Classical rotational rheology as well as two microrheology methods, Multiple Particle Tracking (MPT) and Diffusing Wave Spectroscopy (DWS), were used to investigate the sol-gel transition of a ternary silica-Pluronic F127-starch thermosensitive system. Findings: Classical rheometry and DWS indicated sol-gel transition temperature similar to 25 degrees C at 1 wt% Pluronic, independently of the concentration of the other components. DWS showed a fast gelation process, less than two minutes for all samples, beside a second slow kinetic process. In the gel state, MPT indicated micro-structural and micro-viscoelastic differences compared to rotational rheology. This was explained by formation of an elastic matrix of silica and polymers in combination with assembly of silica particles in large macroporous agglomerates. Presence of starch led to breakdown of the macro porous network, leaving the homogeneous elastic network left.

Creating efficient water-borne dispersions based mainly on renewable materials for coating of flexible packaging paper was the aim of this study. The effects of an ethylene modified poly(vinyl alcohol) grade and a standard poly(vinyl alcohol) on the oxygen and water vapor barrier performance of corn starch and potato starch coatings was studied. The results showed that a coating composition with a high fraction of a renewable polymer was effective in keeping the oxygen barrier at a technically and commercially applicable level. An ethylene modified poly(vinyl alcohol) grade was found to provide lower oxygen transmission rates at high relative humidity, as compared to a standard poly(vinyl alcohol) grade. The oxygen barrier properties of blends of starch and poly (vinyl alcohol) were similar to that of the pure modified poly(vinyl alcohol) in the range from 0% starch to 60% starch. This was observed with both hydroxypropylated and octenyl succinate modified starch grades. The drying conditions of the mixed starch:poly(vinyl alcohol) coatings were based on drying trials with pure poly (vinyl alcohol) coatings. Drying at moderate temperatures indicated the possibility to slightly decrease water vapor transmission rate by higher drying temperature. Several secondary effects of increased drying temperature such as coating hold-out and formation of defects may also be of importance.

Starch and poly(vinyl alcohol) based barrier coatings for flexible packaging papers were studied. Both octenyl succinate modified and hydroxypropylated corn and potato starches were blended with regular and ethylene modified poly(vinyl alcohol) to increase the water vapor barrier properties and enhance the flexibility of the starch coatings, in order to accomplish superior barrier performance. Phase separation between starch and poly (vinyl alcohol) was studied in detail, both in the solution and in dry draw-down coatings on paper. The barrier performance of the coated paper was evaluated with respect to water vapor transmission rate. Conditions for the creation of a thin surface layer consisting of only one of the pure polymers were identified and discussed in terms of phase separation in solution migration of poly(vinyl alcohol) to the uppermost surface layer. The phase separation promoted low water vapor transmission rates also with a rather high fraction of starch in the coatings