Extrusion of plastics

H. R. Jacobi, S crew Extrusion of Plastics, Life Books Ltd., London, 1963. 

It has been suggested by producers of brominated flame retardants that the health risks related to the extrusion of plastics containing PBB and PBDE could be avoided by strengthened worker protection measures In the recycling installations. As an example It was recommended that workers carry protection masks. Clearly, the substitution of the concerned substances would provide the best protection of the concerned workers." European Parliament and Council, 2002. 

Simonds HR, Weith AJ, Schack W. Extrusion of Plastics, Rubber and Metals. New York Reinhold Publishing, 1962 10,001. 

The viscous dissipation term is normally not important. Its significance has been considered in connection with lubrication theory (VI), flow through tubes (B20), extrusion of plastics melts (BIO), and viscometry in rotating-cylinder systems (W6). There is also an additional contribution to the energy flux vector describing energy transport by radiation. See discussion in connection with Eq. (29). 

A few patents have been issued covering the use of screw presses [39], but they do not include details of the design of the presses. However these do not differ from the screw presses widely used for extrusion of plastic rods, tubes and other shapes. A detailed description of the screw presses used in plastics technology can be found in monographs [40, 41]. A diagrammatic representation of a screw press is given in Fig. 266. 

Screw extruders usually are built with a single screw as shown, but may have as many as four screws and the die may have multiple holes of various cross sections. An 8 in. dia screw can have a capacity of 2000 Ib/hr of molten plastics. Tubing can be extruded at 150-300 ft/min. To make pellets, the extrudate goes to cutting machines in which parts as small as washers can be made at rates as high as 8000/min. The extrusion of plastics is described at length by Schwartz and Goodman (Plastics Materials and Processes, Van... 

Fisher EG and Whitfield EC, "Extrusion of Plastics", Wiley, New York, 1976. 

FIGURE 14-24 The calibrator used in the extrusion of plastic pipes. 

Extrusion of plastic clays from source beds... 

Agglomeration by extrusion of plastic material or of particulate matter containing binders through bores of dies in pelleting machines . 

The quasi-continuous extrusion of plasticized materials, mostly mixtures of steam-conditioned animal feeds and binders, such as molasses, through bores in differently shaped dies by press rollers (see Figure 180), was developed during the first part of this century. Today, the process, which is called pelleting, is used for the manufacture of cylindrical extrudates from many pasty, plastic, or deformable materials. 

Figure 4.31 Laboratory unit for the degradative extrusion of plastic wastes.111...

Viscosity of the products obtained by degradative extrusion of plastic mixtures as a function of the shear rate.1... 

A term slip modifier is often used in extrusion of plastics and composite materials where slip-stick of the hot melt at the die is typically observed at too slow or too fast melt flow (see Chapter 17). To avoid confusion, we will use in this chapter the term slip enhancer or friction enhancer. Friction enhancer is a material that increases friction between two surfaces so as to attain a specihc friction level in a controlled manner. 

Colorflol. [Colorco] liq. color dispersions for use in inj. molding, blow molding, and extrusion of plastic resins. 

Fisher, E. G., Extrusion of Plastics, Plastics Institute Monograph, Iliffe, London (1958). 

Miladinov et al. reported the preparation of starch-fatty acid esters by reactive extrusion of plasticized starch and acid anhydrides (acetic, propionic, heptanoic and palmitic anhydrides) in the presence of sodium hydroxide as a catalyst [87]. Starch esters have been prepared by REX using maleic anhydride (MA) as a cyclic dibasic acid anhydride in the presence of 20 wt% glycerol as plasticizer. This material was melt-blended with biodegradable polyester. 

Like the extrusion of metals, the extrusion of plastics involves the continuous forming of a shape by forcing softened plastic material through a die orifice that has approximately the geometric profile of the cross-section of the work. The extruded form is subsequently hardened by cooling. With the continuous extrusion process, such products as rods, tubes, and shapes of uniform cross-section can be economically produced. Extrusion to obtain a sleeve of the correct proportion almost always precedes the basic process of blow molding. 

Figure 9.12. Illustration of the phenomenon of interfacial instability with co-extrusion of plasticized starch/polyester systems [MAR 01b]...

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