Wet pressing

The area of the polar diagram is related to variables such as refining and wet press pressure. The load-elongation curve during tensile testing also shows marked differences in the two directions (Figure 4.8). 

Figure 1 illustrates a typical particle size distribution of some feed mill pulp fractions. The distribution of wet press cake and dried pulp fractions were similar in that a fraction of the particles were about 1 mm with another fraction distributed in the 2 to 5 mm range (2). The major particle distributions of the meal and dust portions of the fines were below 1 mm. 

Aftertreatment of substantive dyeings with cationic organic substances has lately begun to gain in importance. Improvements are obtained in particular in wetfastness properties, especially fastness to water, washing, and wet pressing, as well as fastness to perspiration and cross-dyeing. 

Wet/Wet Pressing, Representative press cycles, conceptual schematics of mass transfer in the sheet, and density profiles through the thickness of the sheet are portrayed in Figure 7, Pressing of wet mats starts with a steady pressure rise to 400 psi platen pressure so as to compress the mat to minimum void volume and express water retained from cold pressing. Platen steam pressures up to 400 psig heat the mat and reduce water viscosity and raise its vapor pressure. This high-presstire inversion cycle is followed by a period of low platen pressure intended to dry the sheet to anhydrous condition. 

WET PRESSING. Where wet presses have a plain roll in direct contact with the wet paper web, serious difficulties have been encountered, attributed to hydrolysed and poorly retained neutral size residues (22). These are deposited on the surface of the roll, building up a film to which the wet web adheres, causing wrap rounds and web breaks. If no solution can be found, this would be a big enough problem to preclude running neutral/alkaline particular attention needs to be paid to minimising pre-hydrolysis and maximising size retention. 

Property Unit polymer Isotropic Extruded Wet pressed... 

Figure 13.19. A papemiachine (not to scale, the dryer section is mnch longer than the Fourdrinier and wet press section).

Relatively low molecular weight polymers such as polyacrylamides or polyvinylamines are widely used as synthetic dry strength additives. These offer both economic and quality benefits to the papermaker that could not be obtained through increases in refining or wet pressing. Additions of active resin as low as 0.2% can achieve increases in dry strength of up to 50%. Collateral benefits can include increases in retention, drainage, machine runnability, productivity and reduced raw material costs. 

Source From Paulapuro, H., Developments in Wet Pressing, PIRA Information Services, Leatherhead, Surrey, U.K., 1993. 

C. A. Brebbia, V. G. DeGiorgi, and R. A. Adey, editors. Cathodic protection systems. Section 1 in Simulation of Electrochemical Processes, WET Press, Southampton, U.K., 2005, pp. 1-56. 

Alcan LV63 or Martinal ON904 + 2 wt% BYK W996 Maximum dispersion viscosity for resin transfer moulding is accepted as around 1000 cps. So, under ambient conditions, these 2 dispersions are only suitable for wet press and vacuum moulding. Source of data Ashland Specialty Chemicals ... 

Shen, X. (1996), An Application of Needle Punched Nonwoves in Wet Press Casting of Concrete, PhD Thesis, The University of Leeds, November 1996, p.24. 

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