Spray coating technique asa surface treatment for woodcontaining paper grades

The objective of this work was to introduce the emerging non-contacting spray coating process and compare it to the existing coating techniques. Particular emphasis was given to the details of the spraying process of paper coating colour and the base paper requirements set by the new coating method. Spraying technology itself is nothing new, but the atomisation process of paper coating colour is quite unknown to the paper industry. The differences between the rheology of painting and coating colours make it very difficult to utilise the existing information from spray painting research. Based on the trials, some basic conclusion can be made:The results of this study suggest that the Brookfield viscosity of spray coating colour should be as low as possible, presently a 50 mPas level is regarded as an optimum. For the paper quality and coater runnability, the solids level should be as high as possible. However, the graininess of coated paper surface and the nozzle wear limits the maximum solids level to 60 % at the moment. Most likelydue to the low solids and low viscosity of the coating colour the low shear Brookfield viscosity correlates very well with the paper and spray fan qualities. High shear viscosity is also important, but yet less significant than the low shear viscosity. Droplet size should be minimized and besides keeping the brrokfield viscosity low that can be helped by using a surfactant or dispersing agent in the coating colour formula. Increasing the spraying pressure in the nozzle can also reduce the droplet size. The small droplet size also improves the coating coverage, since there is hardly any levelling taking place after the impact with the base paper. Because of the lack of shear forces after the application, the pigment particles do not orientate along the paper surface. Therefore the study indicates that based on the present know-how, no quality improvements can be obtained by the use of platy type of pigments. The other disadvantage of them is the rapid deterioration of the nozzle lifetime. Further research in both coating colour rheology and nozzle design may change this in the future, but so far only round shape pigments, like typically calcium carbonate is, can be used with spray coating. The low water retention characteristics of spray coating, enhanced by the low solids and low viscosity, challenge the base paper absorption properties.Filler level has to be low not to increase the number of small pores, which have a great influence on the absorption properties of the base paper. Hydrophobic sizing reduces this absorption and prevents binder migration efficiently. High surface roughness and especially poor formation of the base paper deteriorate thespray coated paper properties. However, pre-calendering of the base paper does not contribute anything to the finished paper quality, at least at the coating colour solids level below 60 %. When targeting a standard offset LWC grade, spraycoating produces similar quality to film coating, but yet blade coating being on a slightly better level. However, because of the savings in both investment and production costs, spray coating may have an excellent future ahead. The porousnature of the spray coated surface offers an optimum substrate for the coldset printing industry to utilise the potential of high quality papers in their business.

Miksi etsiä kuvan ja olemisen alkuja? : miksi ei?

Kirjallisuusarvostelu

Effects of Surface Properties and Wood Modification into Direct Printing on Wood

Building industry is a high volume branch which could provide prominent markets for wood based interior decoration solutions. Competition in interior decoration markets requires versatility in appearance. Versatility in wood appearance and added value could be achieved by printing grain patterns of different species or images directly onto wood. The problem when planning wood printing’s implementing into durable applications is basically how to transfer a high quality image or print sustainably onto wood, which is porous, heterogeneous, dimensionally unstable, non-white and rough. Wood preservation or treating, and modification can provide durability against degradation but also effect to the surface properties of wood which will effect on printability. Optimal adhesion is essential into print quality, as too high ink absorbance can cause spreading and too low ink absorbance cause pale prints. Different printing techniques have different requirements on materials and production. The direct printing on wood means, that intermedias are not used. Printing techniques with flexible printing plates or in fact non-impact techniques provide the best basis for wood printing. Inkjet printing of wood with different mechanical or chemical surface treatments, and wood plastic composite material gave good results that encourage further studies of the subject. Sanding the wood surface anti-parallel to the grain gave the best overall printing quality. Spreading parallel to the grain could not be avoided totally, except in cases where wood was treated hydrophobic so adhesion of the ink was not sufficient. Grain pattern of the underlying wood stays clearly visible in the printed images. Further studies should be made to fine tune the methods that already gave good results. Also effects of moisture content of wood, different inks, and long-term exposure to UV-radiation should be tested.

The Possibilities and Dosimetric Limitations of MLC-Based Intensity-Modulated Radiotherapy Delivery and Optimization Techniques

The use of intensity-modulated radiotherapy (IMRT) has increased extensively in the modern radiotherapy (RT) treatments over the past two decades. Radiation dose distributions can be delivered with higher conformality with IMRT when compared to the conventional 3D-conformal radiotherapy (3D-CRT). Higher conformality and target coverage increases the probability of tumour control and decreases the normal tissue complications. The primary goal of this work is to improve and evaluate the accuracy, efficiency and delivery techniques of RT treatments by using IMRT. This study evaluated the dosimetric limitations and possibilities of IMRT in small (treatments of head-and-neck, prostate and lung cancer) and large volumes (primitive neuroectodermal tumours). The dose coverage of target volumes and the sparing of critical organs were increased with IMRT when compared to 3D-CRT. The developed split field IMRT technique was found to be safe and accurate method in craniospinal irradiations. By using IMRT in simultaneous integrated boosting of biologically defined target volumes of localized prostate cancer high doses were achievable with only small increase in the treatment complexity. Biological plan optimization increased the probability of uncomplicated control on average by 28% when compared to standard IMRT delivery. Unfortunately IMRT carries also some drawbacks. In IMRT the beam modulation is realized by splitting a large radiation field to small apertures. The smaller the beam apertures are the larger the rebuild-up and rebuild-down effects are at the tissue interfaces. The limitations to use IMRT with small apertures in the treatments of small lung tumours were investigated with dosimetric film measurements. The results confirmed that the peripheral doses of the small lung tumours were decreased as the effective field size was decreased. The studied calculation algorithms were not able to model the dose deficiency of the tumours accurately. The use of small sliding window apertures of 2 mm and 4 mm decreased the tumour peripheral dose by 6% when compared to 3D-CRT treatment plan. A direct aperture based optimization (DABO) technique was examined as a solution to decrease the treatment complexity. The DABO IMRT technique was able to achieve treatment plans equivalent with the conventional IMRT fluence based optimization techniques in the concave head-and-neck target volumes. With DABO the effective field sizes were increased and the number of MUs was reduced with a factor of two. The optimality of a treatment plan and the therapeutic ratio can be further enhanced by using dose painting based on regional radiosensitivities imaged with functional imaging methods.

Imagining a New Society: Public Painting as Politics in Postwar Finland

The thesis is the first comprehensive study on Finnish public painting, public artworks generally referred to as murals or monumental paintings. It focuses on the processes of production of public paintings during the post-WWII decades in Finland and the complex relationships between the political sphere and the production of art. The research studies the networks of agents involved in the production of public paintings. Besides the human agents—artists, assistants, commissioners and viewers—also public paintings were and are agents in the processes of production and in their environments. The research questions can be grouped into three overlapping series of questions: First, the research investigates the production public paintings: What kinds of public paintings were realised in postwar Finland—how, where, by whom and for what purposes? Second, it discusses the publicness of these paintings: How were public paintings defined, and what aspects characterised them as “public”? What was their relation to public space, public authorities, and audience? And third, it explores the politics of public paintings: the relationship between Finnish public painting, nationalism, and the memory of war. To answer these questions, extensive archival work has been performed, and over 200 public paintings have been documented around Finland. The research material has been studied in a sociological framework and in the context of the political and economic history of Finland, employing critical theories on public space and public art as well as theories on the building of nationalism, commemoration, memory, and forgetting. An important aim of this research was to open up a new field of study and position public painting within Finnish art history, from which it has been conspicuous by its absence. The research indicates that public painting was a significant genre of art in postwar Finland. The process of creating a national genre of public painting participated in the defining of municipal and state art politics in the country, and paintings functioned as vehicles of carrying out the agenda of the commissioning bodies. In the formation of municipal art policies in Finland in the 1950s, public painting connected to the same tendency of democratising art as the founding of public art museums. Public painting commissions also functioned as an arena of competition and a means of support for the artists. Public paintings were judged and commissioned within the realm of political decision-making, and they suggested the values of the decision-making groups, generally conveyed as the values of the society. The participation of official agents in the production allocated a position of official art to the genre. Through the material of this research, postwar public painting is seen as an agent in a society searching for a new identity. The postwar public painting production participated in the creation of the Finnish welfare society as indications of a humane society. It continued a tradition of public art production that had been built on nationalist and art educational ideologies in the late 19th and early 20th century. Postwar public paintings promoted the new national narrative of unification by creating an image of a homogeneous society with a harmonious communal life. The paintings laid out an image of Finnishness that was modern but rooted in the agrarian past, of a society that was based on hard work and provided for its members a good life. Postwar public painting was art with a mission, and it created an image of a society with a mission.