| 1. |
- Barbier, Christophe, 1974-, et al.
(författare)
-
Coating models for an analysis of cracking behavior between folded paper and creased board
- 2012
-
Konferensbidrag (refereegranskat)abstract
- Creasing coated carton board or folding coated magazine paper, result in large strains in the surface layer of the paper product and might result in surface cracks, which decrease the quality of the products. A better understanding of the mechanical properties of coated layers increases the knowledge needed to reduce crack formation in coated fiberbased materials.The crack area on a coated board was measured after creasing and folding and the crack area on a coated copy paper was measured after folding. A clay pigment and a Ground Calcium Carbonate (GCC) pigment were used. The binder was either an S/B latex or an S/B latex combined with starch.
|
|
| 2. |
- Barbier, Christophe, et al.
(författare)
-
Coating models for an analysis of cracking behavior between folded paper and creased board
- 2012
-
Ingår i: 12th TAPPI Advanced Coating Fundamentals Symposium Proceedings, Co-located with the 16th International Coating Science and Technology Symposium, ISCST 2012. - 9781595102201 ; , s. 5-16
-
Konferensbidrag (refereegranskat)abstract
- Creasing coated carton board or folding coated magazine paper, result in large strains in the surface layer of the paper product and might result in surface cracks, which decrease the quality of the products. A better understanding of the mechanical properties of coated layers increases the knowledge needed to reduce crack formation in coated fiberbased materials. The crack area on a coated board was measured after creasing and folding and the crack area on a coated copy paper was measured after folding. A clay pigment and a Ground Calcium Carbonate (GCC) pigment were used. The binder was either an S/B latex or an S/B latex combined with starch. The type of pigment seemed to have the greatest influence on the crack area during creasing and folding of thick board. Clay based coatings showed a larger crack area than the GCC based coatings and coatings containing starch showed generally a larger crack area than the coatings that contained only S/B latex. After folding of thin copy papers, the crack area showed a slightly different pattern. Here, it seemed that the binder was of greater importance than the type of pigment. Coatings containing only latex binder showed a considerably lower crack area than the coatings containing both latex and starch binders. The clay based coatings also showed similar crack areas as the GCC based coatings. A micromechanical model was used to estimate the in-plane and out-of-plane mechanical properties of clay based- and GCC based- coating layers. The clay-based coatings showed an anisotropic material behavior with considerably lower stiffness and strength during out-of-plane compared to in-plane. GCC based coatings, on the other hand, showed an isotropic material behavior with similar in-plane and out-of-plane properties. The calculated material behavior of coating layers, together with the data from the literature was used to explain the difference in cracking behavior between Clay- and GCC- based coatings during creasing of thick coated board and folding of thin coated copy paper.
|
|
| 3. |
|
|
| 4. |
- Hallberg Hofstrand, Erik, et al.
(författare)
-
Dynamic Measurements of Nip Force Variations during Post-Printing of Corrugated Board
- 2006
-
Ingår i: Nordic Pulp & Paper Research Journal, 21(1), 111-114 (2006).
-
Tidskriftsartikel (refereegranskat)abstract
- A method has been developed in order to measure nip force variations during flexographic post-printing of corrugated board. This method can be used to study the influence of the nip mechanics on the final print quality
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Hallberg Hofstrand, Erik, 1975-
(författare)
-
Flexographic Post-Printing of Corrugated Board : Contact Mechanics and Print Quality
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As the corrugated board industry strives to produce products with a higher print quality in the converting stage, there is a need for a greater understanding of the factors influencing the final print quality and how we perceive the print. In this work, a method for quantifying the print quality of printed corrugated board is presented as well as methods that quantitatively characterize the mechanical interaction between the printing form and the corrugated board in the printing nip. The results of investigations addressing the impact of the mechanical properties of the printing form on ink transfer are also presented. A band-pass image analysis method adapted to the spatial wavelength of B-flute corrugated board was used to quantify the print quality on the board in terms of print banding. The findings were substantiated by a perceptual evaluation which showed a high correlation to the instrumental quantification. The main cause of print banding is a higher local contact pressure on the fluting tips than in the fluting valleys, which leads to a higher ink transfer to the fluting tips. A greater difference between the local contact pressure on the fluting tips than in the fluting valleys generated a higher degree of banding. The difference in local contact pressure as well as nip force variations could be measured using the proposed methods to characterize the interaction between the printing form and the corrugated board. The difference in local contact pressure was highly dependent on the mechanical properties of the components of the printing form. An increase in the stiffness in compression mode and in the bending stiffness of the printing form led to a smaller contact area in the printing nip and consequently a higher external pressure on the ink, resulting in an overall higher ink transfer but also a higher degree of banding. The influence of the mechanical properties of the printing form components was supported by the results of numerical simulations of the contact between the printing form and the corrugated board. Contact area, pressure level and texture of the local contact pressure were compared with measurements of local contact pressures for different printing forms and the results showed a high degree of agreement. Numerical simulations could thus predict the print quality achieved with different printing forms under different printing conditions.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
- Javed, Asif, 1982-, et al.
(författare)
-
Crack analysis of barrier coatings based on starch and starch-PVOH with and without plasticizer
- 2018
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:2, s. 336-347
-
Tidskriftsartikel (refereegranskat)abstract
- 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 > 10000 cm 3 / m 2 day\text{OTR}>10000\hspace{0.1667em}{\text{cm}}^{3}/{\text{m}}^{2}\hspace{0.1667em}\text{day} 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.
|
|
| 14. |
|
|
| 15. |
- Javed, Asif, 1982-
(författare)
-
Effects of plasticizing and crosslinking on coatings based on blends of starch-PVOH and starch-lignin
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A barrier material is usually needed on a fiber-based food package to protect the packed food from gases and moisture and thus maintain its quality. Barrier materials presently used in food packaging applications are mostly petroleum-based polymers. Over the last few decades, efforts have been made to replace petroleum-based materials with bio-based materials. The present work has focused on the possibility of using a natural barrier material on a fiber-based food package and the effects of plasticizing and cross-linking on the mechanical and barrier properties, and the stability in water of coatings based on starch-poly(vinyl alcohol) (PVOH) and starch-lignin blends.The flexibility of the starch films was increased by adding PVOH further by adding a plasticizer. It was shown that citric acid can act as a compatibilizer and cross-linker for starch and PVOH, and the use of citric acid may slow down the diffusion of both oxygen and water vapor if a multilayer coating strategy is used. The addition of polyethylene glycol to the pre-coating recipe resulted in a lower oxygen transmission rate through polyethylene-extruded board than when citric acid was added to the pre-coating. The flexibility of the barrier coatings and the properties of the base substrate affect the cracking tendency of the barrier coatings during the creasing and folding of a barrier-coated board.The addition of lignin to the starch reduced the migration of starch from the starch-lignin films and the addition of ammonium zirconium carbonate as a cross-linker reduced the migration of both starch and lignin from the films. The addition of starch to the lignin solution increased the solubility of lignin at low pH, and the pilot-coated board showed a significant decrease in migration of lignin from the coatings containing ammonium zirconium carbonate when the pH of the coating solution was decreased.
|
|
| 16. |
- Javed, Asif, 1982-
(författare)
-
Effects of plasticizing and crosslinking on the mechanical and barrier properties of coatings based on blends of starch and poly(vinyl alcohol)
- 2015
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the last decades, intensive research has been carried out in order to replace oil-based polymers with bio-based polymers due to growing environmental concerns. So far, most of the barrier materials used in food packaging are petroleum-based materials. The purpose of the barrier is to protect the packaged food from oxygen, water vapour, water and fat. The mechanical and barrier properties of coatings based on starch-plasticizer and starch-poly(vinyl alcohol) (PVOH)-plasticizer blends have been studied in the work described in this thesis. The plasticizers used were glycerol, polyethylene glycol and citric acid. In a second step, polyethylene coatings were extruded onto paperboard pre-coated with a starch-PVOH-plasticizer blend. The addition of PVOH to the starch increased the flexibility of the film. Curing of the film led to a decrease in flexibility and an increase in tensile strength. The flexibility of the starch-PVOH films was increased more when glycerol or polyethylene glycol was added than citric acid. The storage modulus of the starch-PVOH films containing citric acid increased substantially at high temperature.It was seen that the addition of polyethylene glycol or citric acid to the starch-PVOH blend resulted in an enrichment of PVOH at the surface of the films. Tensile tests on the films indicated that citric acid acted as a compatibilizer and increased the compatibility of the starch and PVOH in the blend. The addition of citric acid to the coating recipe substantially decreased the water vapour transmission rate through the starch-PVOH coated paperboard, which indicated that citric acid acts as a cross-linker for starch and/or PVOH. The starch-PVOH coatings containing citric acid showed oxygen-barrier properties similar to those of pure PVOH or of a starch-PVOH blend without plasticizer when four coating layers were applied on a paperboard. The oxygen-barrier properties of coatings based on a starch-PVOH blend containing citric acid indicated a cross-linking and increase in compatibility of the starch-PVOH blends.Polyethylene extrusion coating on a pre-coated paperboard resulted in a clear reduction in the oxygen transmission rate for all the pre-coating formulations containing plasticizers. The addition of a plasticizer to the pre-coating reduced the adhesion of polyethylene to pre-coated board. Polyethylene extrusion coating gave a board with a lower oxygen transmission rate when the paperboard was pre-coated with a polyethylene-glycol-containing formulation than with a citric-acid-containing formulation. The addition of polyethylene glycol to pre-coatings indicated an increase in wetting of the pre-coated paperboard by the polyethylene melt, and this may have sealed the small defects in the pre-coating leading to low oxygen transmission rate. The increase in brittleness of starch-PVOH films containing citric acid at a high temperature seemed to have a dominating effect on the barrier properties developed by the extrusion coating process.
|
|
| 17. |
- Javed, Asif, 1982-, et al.
(författare)
-
Lignin-containing coatings for packaging materials
- 2018
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:3, s. 548-556
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 18. |
- Javed, Asif, 1982-, et al.
(författare)
-
Lignin-containing coatings for packaging materials—pilot trials
- 2021
-
Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 13:10
-
Tidskriftsartikel (refereegranskat)abstract
- 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. © 2021 by the authors
|
|
| 19. |
|
|
| 20. |
- Johnson, Johanna, 1970-
(författare)
-
Aspects of Flexographic Print Quality and Relationship to some Printing Parameters
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Flexographic printing is a common printing method in the packaging field. The printing method is characterized primarily by the flexible printing plate and the low viscosity inks which make it suitable for use on almost any substrate. The object of this study was to obtain further knowledge of the some important mechanisms of flexographic printing and how they influence the print quality. The thesis deals with printing primarily on board and liner but also on newsprint with water-borne ink using a full-scale flexographic central impression (CI) printing press. Several printing trials have been performed with a focus on the chemical interaction between the ink and substrate and the physical contact between the ink-covered printing plate and the substrate. Multicolour printing exposes the substrate to water from the water-containing ink. The emphasis was to investigate the relation between print quality and water-uptake of the paper surface with heat and water. Printing trials was carried out on substrates possessing a hydrophobic, and also a rather hydrophilic surface using a regular commercial water-borne ink. The favorable effect which water or surfactant solution had on the hydrophobic substrate with regard to print mottle could depend on its surface compressibility in combination with the hydrophobic nature of its surface that could affect the wetting properties. Conventional printing involves physical contact between plate and ink and between ink and substrate. A method for measuring the dynamic nip pressure using thin load cells is presented. Print quality was influenced by the plate material. A correction procedure taking into account the size of the sensor was developed in order to estimate the maximum dynamic pressure in the printing nip. An attempt was made to identify essential mechanical and chemical parameters, and also geometrical properties of the plate that affected print quality. Laboratory printing trials were carried out and a multivariate analysis was applied for evaluation of print quality data. The impact of the plate properties on print quality was evident. The essential properties of the plate that influence print quality were the small-scale roughness and long-scale roughness.
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
- Johnson, Johanna, et al.
(författare)
-
Measuring the Dynamic Nip Pressure in a Flexographic CI-Printing Press
- 2004
-
Ingår i: Nordic Pulp and Paper Journal, vol.19,2004,pp 84-88.
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamic pressure in a flexographic printing press was measured and the influence of impression, speed and choice of printing plate on the dynamic pressure was analysed. The measurements were complemented by measurements to assess the ink transfer to the substrate
|
|
