Blow processings

Andre, J. M. ct al., 1998. Numerical modelling of the polymer film blowing process. Int. J. Forming Processes 1, 187-210. 

Steam Active Reforming Steam-blowing process Steam ejectors Steam explosion Steam gasification Steam generator... 

The one-time important applications in photographic film, in bicycle parts (pump covers and mudguards) and in toys manufactured by a blowing process from flat sheet are no longer of importance. 

Although plastic sheet and film may be produced using a slit die, by far the most common method nowadays is the film blowing process illustrated in Fig. 4.20. The molten plastic from the extruder passes through an annular die and emerges as a thin tube. A supply of air to the inside of the tube prevents it from collapsing and indeed may be used to inflate it to a larger diameter. 

Most rigid polyurethane foams have a closed cell structure. Closed cells form when the plastic cell walls remain intact during the expansion process and are not ruptured by the increasing cell pressure. Depending on the blowing process a small fraction (5-10%) of the cells remain open. Closed cell structures provide rigidity and obstruct gaseous or fluid diffusional processes. 

Schuler, F. (1959), Ancient glassmaking techniques The blowing process, Archaeology 12, 47-53, 116-120. 

An early problem was that the blowing process as originally developed produced rounded bases, and so the bottles could not be stacked upright on shelves. Initially, bottles were equipped with separately moulded base cups, usually made from polyolefin and readily attached by a snap-on or glue-on process. The Continental Group then introduced in the USA a bottle with a shaped multilobal bottom that did not require a base cup, and further designs have followed [64],... 

Blown, or oxidized, petroleum asphalts were first produced commercially by Byerley about 1894. But neither blown nor residual asphalts from the early crudes enjoyed very good repute in the United States, partly because of the nature of the crudes and partly because of insufficient care in manufacture. Discovery of sources of asphaltic and semi-asphaltic crudes made possible the production of residual petroleum asphalts suitable for paving, and improvements in the blowing process led to products well suited for the manufacture of prepared roofings. In fact, the early growth of the roofing industry corresponded closely with the production of petroleum asphalts (86). 

Melt Blowing. The melt blowing process uses very high melt flow polymers, sometimes in excess of 400 dg/min, and extrusion and tempeiatuies above 300°C to pioduce very fine fibeis (<5 pm dia). 

Despite the non-isothermal nature of the film blowing process we will develop here an isothermal model to show general effects and interactions during the process. In the derivation we follow Pearson and Petrie s approach [20], [19] and [21]. Even this Newtonian isothermal model requires an iterative solution and numerical integration. Figure 6.21 presents the notation used when deriving the model. 

Figure 6.21 Schematic diagram of the film blowing process.

Figure 6.23 Predicted film blowing process using an isothermal Newtonian model for a...

J.R. Pearson and C.J.S. Petrie. A fluid-mechanical analysis of the film-blowing process. Plast. 

An alternative way of producing film is the blowing process. An annular die is used, from which the material emerges as a thin-walled tube, which is immediately blown-up by internal pressure to a much larger diameter (Figure 11.26). 

Figure 8-7. Schematic diagram for film blowing process.

Moore, S., Two-Stage Stretch (Injection) Blow Process Claims Benefits for Drink Cups, MP, Jan. 2003. 

Both injection blow molding and pinch tube processes are especially suitable for metallic pigments, because the expansion of the plastic during the blowing process causes further orientation of the metallic pigment parallel to the surface. 

Stretch-blow processing is used to develop biaxial molecular orientation. If blow pressure alone were used, the stresses in the preform wall would be predominantly circumferential, producing orientation only in the hoop direction of the bottle. However, the additional stresses generated longitudinally by the stretch rod result in biaxial orientation. 

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