Roller drawing

Figure 10.2 Offset lithography rollers. (Drawing courtesy of Boris Listdat.)... 

Die drawing allows bars, tubing, and large-size sheets to be obtained. The polymer is drawn through a heated die with a conically shaped entrance. Sheets of oriented polymer can be produced by roller drawing while highly oriented films and rods can be obtained by co-extmsion. 

Kaito A, Nakayaina K and Kanetsuna H (1986) Roller drawing of polyoxymethylene, J Appl Polym Sci 32 3499-3513. 

The film tube is collapsed within a V-shaped frame of rollers and is nipped at the end of the frame to trap the air within the bubble. The nip roUs also draw the film away from the die. The draw rate is controlled to balance the physical properties with the transverse properties achieved by the blow draw ratio. The tube may be wound as such or may be sHt and wound as a single-film layer onto one or more roUs. The tube may also be direcdy processed into bags. The blown film method is used principally to produce polyethylene film. It has occasionally been used for polypropylene, poly(ethylene terephthalate), vinyls, nylon, and other polymers. 

The copolymers are used in the manufacture of filaments. These may be extruded from steam-heated extruders with a screw compression ratio of 5 1 and a length/diameter of 10 1. The filaments are extruded downwards (about 40 at a time) into a quench bath and then round drawing rollers which cause a three- to four-fold extension of the filaments and an increase in strength from about 10000 to 36 000 Ibf/in (70-250 MPa). The filaments are used for deck chair fabrics, car... 

Components for welding, tube drawing, and extruders. Ball and roller bearings. 

The amorphous PEN resin pellets are first dried at 180 °C and then extruded at 290-300 °C through a die, formed into a sheet, which is then followed by a two-step orientation (forward draw and sideway draw process) just above the glass transition temperature (Tg) (>120°C). After the orientation process, the PEN film is conveyed between rollers at 210-220 °C to induce crystallization. At the end of the orientation and crystallization process, the film is cut and rolled into widths and lengths to suit individual customers [14-16], Two of the process used to produce such films are shown in Figure 10.3. 

Be own s patent squeezer is acknowledged to be very effective. It consists of a series of massive rollers, so arranged that the heated bloom of puddled iron, being placed on the top of the machine, is taken in between the two upper rollers, and is gradually compressed between these and others as it descends. At the bottom, it falls upon an endless revolving chain ladder, by which it is elevated and thrown on to a platform in front of the rolls for drawing it out into bars. 

Cast film extrusion. In a cast film extrusion process, a thin film is extruded through a slit onto a chilled, highly polished, turning roll where it is quenched from one side. The speed of the roller controls the draw ratio and final film thickness. The film is then sent to a second roller for cooling of the other side. Finally, the film passes through a system of rollers and is wound onto a roll. A typical film casting process is depicted in Figs. 3.53... 

Where still used, cold drawing consists essentially of removing the yam from the package prepared in the melt spinning operation and feeding it forward at a uniformly controlled rate under low tension. It is passed around a godet or roller that determines the supply rate and prevents slippage for nylon 66, it then is wrapped several times around a stationary... 

One way to apply such moderate pressure is to enclose the wet-liquid resin material and mold in a flexible membrane or bag, and draw a vacuum inside the enclosure. Atmospheric pressure on the outside then presses the bag or membrane uniformly against the wet lay-up. An effective pressure of 69-283 kPa (10 to 14 psi) is applied to the product. Air is mechanically worked out of the lay-up by hand usually using serrated rollers. The vacuum direcdy helps to remove air in the wet lay-up via techniques such as using bleeder channels within the bag (using material such as jute, glass wool, etc.) to aid in the removal of air and also to permit drainage of any excess resin. This layup is than exposed to heat using an oven or heat lamp. 

---