Paper surface

Fluidyibsorbamy. Fluids like ink penetrate into paper during the printing process. The further the ink penetrates, the less glossy the print. The degree of penetration in paper is generally a function of the paper porosity and wettabiUty by the fluid. It can be controlled by the particle size, shape, and chemical nature of the filler or filler surface. In particular, plate-like fillers, such as clays, tend to produce the best fluid holdout because they tend to overlap and reduce the porosity at the paper surface (see Inks). 

Curl Control. Many grades of paper tend to cud, especially as humidity varies, because of the stresses produced duting the dryiag process. This is especially troublesome when only one side of the paper receives a surface treatment. Judicious appHcation of water to the opposite side of the dry sheet followed by redryiag may correct the curling. Water may be appHed by surface appHcation at the size press, water box, or calender stack or it may be sprayed on. Small amounts of water can be appHed to the paper surface as a foam with exceUent results. 

Filiform corrosion is characterised by the formation of a network of threadlike filaments of corrosion products on the surface of a metal coated with a transparent lacquer or a paint him, as a result of exposure to a humid atmosphere. This phenomenon first attracted attention because of its formation on lacquered steel, and for this reason it is sometimes referred to as underfilm corrosion, but although it is most readily observed under a transparent lacquer it can also occur under an opaque paint film or on a bare metal surface. Filiform corrosion has been observed on steel, zinc, magnesium and aluminium coated with lacquers and paints, and with aluminium foil coated with paper. Surface treatment of the metal by phosphating or chromating lessens the tendency for filiform corrosion to occur, but it is not completely... 

Dry heat only Temperature-sensitive chemical Usually a temperature-sensitive white wax concealing a black marked or printed (paper) surface at a predetermined temperature the wax rapidly melts exposing the background mark(s) Temperature... 

Valuable results with Tof-SIMS imaging have been obtained e.g., with paper samples. The distribution of papermaking chemicals on the surface of coated and uncoated papers is very important for its further treatment, such as printing. Figure 16 [70] is an example of use of the technique for chemical microscopy analysis of paper surfaces. 

Figure 16 ToF-SIMS images of total ion current, AKD (alkyl ketene dimer) size, optical brightener and hexosan distribution on multipurpose paper surface after coating with Au-Pd. Reproduced from Fardim and Holmbom [70], with permission from Elsevier. 2005.

The particular colors that are observed at different angles will depend critically on the thickness of the thin film coating. Precision instrumentation is required to carefully control film thickness during production. The magnitude of the optical effect depends on the density of flakes in the ink, while the quality of the optical effect depends on the precise orientation or alignment of these flakes with respect to the paper surface. 

The data matrix is preprocessed using any signal enhancement technique to obtain the spectroscopic data of greatest interest as it relates to the spatial characteristics of the material or sample surface under study. In this particular case each data point represents the absorbance difference between a no absorbing wavelength for the paper surface and an absorbing wavelength for the transparent ink added to the paper. The difference in... 

Table 75-1 Simulated absorbance data depicting an ink pattern on a two-dimensional paper surface with spatial dimensions X and Y...

A further problem of the size press operation is that of films splitting. At the exit of the nip, the film sometimes splits into two layers with one part following the paper and the other remaining on the roll surface. The problem manifests itself as small scale nonuniformities on the paper surface caused by threads of the size solution being drawn out and deposited unevenly on the surface to give a kind of orange peel effect. 

Areas of application include wood coloration [45], paper mass coloration [46] and paper surface coating in the lime press [47], the office articles and artists colors sector pigments are used in colored pencils, crayons, and writing and pastel chalks or in water colors, as well as in cosmetics, especially soap [48],... 

P.R.188 is also employed in paper mass coloration, paper surface coloration, paper pulp, and paper spread-coating formulations, as well as in wallpaper and wax crayons. 

Incorporated in plasticized PVC, P.B.15, like other phthalocyanine pigments, is usually entirely fast to migration. Moreover, it provides excellent lightfastness. P.B.15 also finds use in various types of PUR foam materials as well as in rubber. Its redder and frequently cleaner shade compared to corresponding stabilized types makes it an equally useful pigment for other media. This applies especially for water-based systems. Textile printing, paper mass coloration, paper surface treatment, and paper pulp are areas of application as suitable for the use of P.B.15 as office articles, including colored pencils, blackboard chalks for schools, and water colors. 

As is clear from Table 2, zinc plates gave relatively deep images compared with those of the Photopolymer Plate. However, there is not much difference in the depth between those stereos obtained from zinc plates and the Photopolymer Plate, as shown in Table 3. This means that in reproduction work from a paper mold into a stereo, even if an effort is made to give more depth beyond necessity, it is not actually reproduced in the stereo. The Photopolymer Plate can show a satisfactory reproduceability if it has 30-40 urn depth in the shadow area. Further evaluations were made on isolated lines (in case of 60-150 jim line width) and depth in reverse area for their reproduceability onto paper surface, and the results were more stable than those with metal plates. Stereos can be also made with polypropylene as well as with lead. 

Back, E.L. and Danielsson, S. (1987). Oxidative activation of wood and paper surfaces for bonding and for paint adhesion. Nordic Pulp and Paper Research Journal, 2(special issue), 53-62. 

Fig. 1. The core particle, the DNA superhelix and H2B and H3 N-terminal tails, (a) Space-filling representation of the 2.8 A crystal structure of the 146 bp human a-satellite nucleosome core particle [22]. The dyad is in the plane of the paper and the superhelix axis slightly off that plane. Positive and negative numbers mark the superhelix locations (SHL) in the upper and lower gyres, respectively, and the dotted curve follows the path of the double helix axis, (b) Ribbon representation of the DNA superhelix slit along a line parallel to its axis, opened out and laid flat on the paper surface. SHL are also indicated, together with H2B and H3 tails passage points between the gyres. (From Fig. 5 in Ref [29].)...

Alum has two prime uses. About two thirds of it is bought by the pulp and paper industry for coagulating and coating pulp fibers into a hard paper surface by reacting with small amounts of sodium carboxylates (soap) present. Aluminum salts of carboxylic acids are very gelatinous. 

Starch glues are water dispersions for libraiy paste and wallpaper paste. They coat paper for better receptivity of inks and keep the inks held out on the paper surface. They are also used in corrugated cardboard and paper laminating. 

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