Paper porosity

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). 

Automatic. This can take prefolded, sheet-fed, or roll-fed leaflets and present them to be pushed into the carton by the product. In comparison to manual and semiautomatic operation, automatic equipment is very sensitive to paper porosity, physical size, paper calliper, fold design and accuracy, flying leaves, and so on, and has difficulty with two different size leaflets. 

Figure 1 shows the comparison of theory for the trickling-pulsing transition with experimental results from pilot scale columns for air-water systems. Since most experimental studies did not mention the pressure inside the column, a value of 1.5 atm has been assumed. The agreement with the data of Weekman and Myers (1) is excellent and a good agreement with that of Chou et al. (8) is attained up to moderate gas flow rates. The theory would appear to be in poor agreement with Sato et al. however, in Sato s paper, porosity was not mentioned. Experimental data... 

The other parameter of lightweight paper to be considered is the porosity of the chosen paper. This is because many cartoning machines use a vacuum type of pickup for the leaflet no matter in what form it may be presented to the cartoning machine. Even so-called reel-fed leaflets have to be cut, picked and moved through folding plates up to the insertion point into the carton. For this reason both specification of paper porosity to air and pick tests (to keep down the amount of lint or dust) are sensible. 

Because of its vapor pressure properties, phenol is present in both the particulate phase and the vapor phase of cigarette MSS aerosol. Thus, it is amenable to removal from the vapor phase by selective filtration and to reduction of its level in the particulate phase by all the technologies whereby MSS particulate phase or tar delivery is reduced, for example, filtration efficiency, air dilution (increased paper porosity, filter-tip ventilation), and inclusion of expanded tobacco in the blend. 

TSNAs, because of their low volatility, occur predominantly in the MSS particulate phase and behave similarly to other particulate-phase components such as the PAHs, that is, they are not selectively reduced by hltration with plasticized cellulose acetate. However, Hoffmann et al. (1685) noted that MSS TSNA yields are reduced by any technology designed to reduce the MSS particulate phase, such as increased hltration efficiency, increased air dilution (hlter-tip perforation, paper porosity), and tobacco expansion. 

Air dilntion by increased paper porosity and/or ventilated hlter tips (Hoffmann et ah, 1984). 

The oxygen level in the tobacco rod a short distance (1-2 mm) behind die tobacco rod-fire cone interface is influenced by diluting air entering die tobacco rod through the cigarette paper and this diluting air increases as die cigarette paper porosity increases. 

Air dilution (increased paper porosity, filter tip perforations)... 

The temperature of the room should be measured at the beginning and at the end of the extraction, as well as the temperature of the extracting solution in the bottle at the end of the shaking period. The extracts should be immediately filtered through a filter paper (porosity 0.4-1.1 pm capable of retaining particles of 2.7 pm size) previously rinsed with 0.05 mol L EDTA followed by distilled water. The filtrates should be collected in polyethylene bottles. Blank extractions i.e. without soil) should be carried out for each set of analyses using the same reagents as described above. 

The dry strength of paper relates strongly to the distribution of fibres and bonds (controlled by the formation process) and the mechanical properties of the fibres. Surface chemistry plays the main role in the development and strength of fibre-fibre bonds. Fibres are often chemically and/or mechanically refined to increase bond areas and strength. This is not always desired since it may slow down drainage and decrease the paper porosity, which may result in loss of bulk, and detrimentally affect stiffness, tearing resistance and opacity. 

Both natural wood pulp fibres and staple viscose fibres dominate wet-laid filter media, and their pulp fibres are available from various lengths ranging from 1 to 12 mm in many special geometries and shapes these cross sections include traditional round, flat and grooved, ttilobal, C-shaped and V-shaped, hollow, and cross-shaped fibres. Round fibres with a smaller diameter have less impact on the pressure drop, and they have a positive influence on strength of paper filter made from wood pulp. Tri-lobal fibres have a similar influence on paper porosity to round fibres, but have improved particle capture capacities. 

The resins used in air and oil filters are moderate-to-low molecular weight, catalyzed by caustic in one step 10—20% alcohol is added soHds content is in the range of 50—60%. These resins are designed to penetrate the sheet thoroughly, yet not to affect the porosity of the paper. In the B-stage, the resin must have sufficient flexibiHty to permit pleating the C-stage should have stiffness and resistance to hot oil. 

Paper printabdity, its ability to be ink-receptive, is determined by smoothness, absorbency, porosity, and ink holdout capability. 

Surface Sizing. Surface sizing is generally used for modification of other properties of paper or paperboard such as printabiHty, smoothness, porosity, coefficient of friction, opacity, surface strength, anti-linting or coating holdout. Anionic starch is perhaps the most common additive or co-additive used for surface sizing. 

Oil Repellent. Fluorochemicals are the only class of material that can provide oil repeUency without altering the porosity of the paper or paperboard. Physical barriers to oil penetration are used primarily for their moisture- or gas-barrier properties, with retarded oil penetration as a secondary benefit. The most common od-repeUent additives are long-chain perfluoroalkyl phosphate salts of ammonia or diethanol amine. Commercial sources include Scotchban (3M), Zonyl (DuPont), and Lodyne (Ciba Specialties). There are also a fluorochemical carboxylate salt, Lodyne (Ciba Specialties), and fluorochemical copolymers, eg, Scotchban (3M). The widest range of oily fluid holdout is provided by the fluorochemical copolymers. 

A.STM B741, Std. Test Methodfor Porosity in Gold Coatings on Metal Substrates by Paper Electrography, American Society for Testing and Materials, Philadelphia, Pa., 1990. 

Some advantages of paper in electrophoresis are that paper is readily available, easy to handle, and new methodologies can be developed rapidly. The disadvantages of paper electrophoresis are that the porosity of paper caimot be controlled, the technique is not very sensitive, and it is not easily reproducible. 

Figure 13.5 Plug-type dezincification on the internal surface of a brass condenser tube. Note the extreme porosity of the copper plugs. Tube wall thickness was 0.040 in. (0.10 cm). Compare to Fig. 13.13. (Courtesy of National Association of Corrosion Engineers, Corrosion 89 Paper No. 197 by H. M. Herro.)...

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