Hot platen

Figure 12.22. The effects of time on temperature and moisture content within a conventionally pressed panel are shown for different layers within the panel. Layer 1 spans the midpoint of the thickness of the mat while layer 10 is in contact with the hot platen (Humphrey and Bolton, 1989).

Polyethylene. The effect of crystallinity on the diffusion coefficient of iso-octane at 54°C in PE was determined in a sorption experiment. Films of Sclair PE (DuPont Chemical Co., Kingston, Ontario) were compression-molded in a hot platens press at 170°C and were allowed to cool in the press. All films were 200 /xm thick. The properties of the resins are given in Table II. 

The liquid glue-mix spread used was 380 g/m d.g.l. (double glueline), press temperature was 130°C, and pressure was 15 kg/m for both types of panels. Press time was 5 min for the thicker panel type, this being rather short, and 4 min for the thinner one. These press times were chosen because industrial plywood panels are manufactured with press times calculated as 1 min/mm panel thickness to the flirthest glueline from the press hot platen + 2 min. The panels were tested for dry tensile strength according to European Norm EN 314 [25]. 

In this method, after alignment the green sheets are laminated layer by layer on a hot platen and pressure is applied. This is efficient since alignment and lamination are performed at the same time. However, as shown in Figure 7-11, the lowest green sheet is constantly heated, and it is pressed cumulatively many times. Therefore the lowest green sheet looses its flexibility so that the structure of the laminated body in the z axis becomes uneven making the method unsuitable for substrates with many layers. 

Hot platen presses are commonly used for the hot sizing of titanium. The tooling is designed for the hot sizing of preforms that is, it must only hold the workpiece to the required shape for the necessary time at temperature. Hot sizing in hot platen presses is done in the following sequence of operations ... 

In hot plate welding, the parts to be joined are pressed against the hot platen platens ean be eoated with polytetrafluoroethylene (PTFE) to inhibit melt sticking. Welding can be performed in either of two... 

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