Extruding die

If the extruder is coupled to a die which is used to produce two laces for subsequent granulation, calculate the output from the extruder/die combination when the screw speed is 100 rev/min. Each of the holes in the lace die is 1.5 mm diameter and 10 mm long and the viscosity of the melt may be taken as 400 Ns/m. ... 

Example 5.8 It is desired to blow mould a plastic bottle with a diameter of 60 mm and a wall thickness of 2 mm. If the extruder die has an annular slot of... 

Extrusion conditions = 1.25 mil film blown at 2 and 1 blow up ratio using 63.5 mm, 20D smooth bore extruder, die gap 80 mil, melt temperature 193°C. 

There are two types of hot feed extruders, one similar to the screw type cold feed extruder, except that the strip feeding the extruder is taken directly off the two-roll mill. The mill is used to further blend and heat the compound. It is then taken off the mill in strip form and fed directly into the extruder. The second type of hot feed extruder is based on the action of a ram being used to feed the compound into the extruder die (Fig. 16). The compound is placed on a two-roll mill to further blend and heat rubber. It is then taken off the mill in pig form to fill the extruder chamber. 

Forming the hinge cross-section by using an extruder die results in a hinge with poor flex life. Because hinges are formed in the direction of the polymer flow, they cannot be sufficiently oriented when flexed. However, if an extruded hinge is formed by the take-off mechanism while the polypropylene... 

Extrudate It is the plastic hot melt as it emerges/discharges/exits from the extruder die s orifice into a desired product form such as film, sheet, etc. 

These include cold drawn, high pressure oriented chain-extended, solid slate extruded, die-drawn, and injection moulded polymers. Correlation of hardness to macroscopic properties is also examined. In summary, microhardness is shown to be a useful complementary technique of polymer characterization providing information on microscopic mechanical properties. 

There is a continuing interest to improve and extend the fimctional properties range of dairy proteins to provide both health benefits and their characteristic physical behaviors under different temperature, moisture, and pH conditions so that they may be included in foods that ordinarily do not contain them. One such research area is the extrusion texturization of whey proteins, which have resulted in dairy proteins with new characteristics imparted by a controlled texturization process, depending on the application desired (Hale et al., 2002 Manoi and Rizvi, 2008 Onwulata, 2009 Onwulata et al., 1998). Protein texturization is a two-step process that involves, first, the unfolding of the globular structure (denaturation) and, second, the alignments of the partially unfolded structures in the direction of mass flow in the extruder. The surface characteristics are imparted at the extruder die as the molten mass exits (Onwulata et al., 2003a). 

Difference in physical properties along and across a section of rubber compound resulting from the passage of the rubber through a mill nip, a calender nip or through an extruder die. See Calender Grain. 

An extruder die-box or head in the shape of a letter T used in wire covering. The rubber flow is thus at right angles to the direction of travel of the wire. 

Production of extruder dies for complex products, such as profiles, requires a method for accurately calculating the required shape of the die and the flow inlets. 

Control of the temperature of rubber compound whilst being processed in extruders and injection moulding machines is vital if the product from these processes is to be uniform in quality. Failure to control temperatures in processing equipment can lead to scorching of the compound as it emerges from the extruder die or injection machine nozzle. Most modem items of processing equipment are fitted to a temperature control unit using either oil or water as the circulatory medium. 

A variety of extruder die heads are used to produce the different tread profiles required for the different tyre types. 

The extmders were monitored using a pair of custom-made transmission probes inserted into the extruder die just downstream from the screws. Each probe consisted of a sapphire window brazed into a metal body a quartz rod behind the window piped the light to the end of the probe low-OH silica fiber-optic bundles connected the probe to the NIR analyzer, an LT Quantum 12001. Optical path lengths were typically between 0.3 and 2.0 cm. 

C did not puff when the products left the extruder die (Figure 15), These extrudates were recognized as "undertex-turzed". The common appearance of these undertexturized products was lack of smooth and continuous surface. A minimum temperature of 138°C was needed to produce puffed and retort-resistant extrudates when other process conditions were held constant. 

Figure 13.. Comparison of theoretical analysis and empirical NMR imaging of fluid flow during extrusion. Limiting cases for theoretical analysis (a), the velocity profile as a function of position with no pressure gradient in the z-direction (b), the velocity profile as a function of position with no net flow through the extruder. Limiting cases for empirical analysis by NMR flow imaging (c), no pressure gradient in the z-direction (die open) (d), no net flow through the extruder (die closed).[Reproduced with permission from Ref.61].

Figures 7.18(b) and 7.18(c) show the breakup into droplets of an extended filament of high density polyethylene in a polystyrene matrix. In Fig. 7.18(b) the distance between the extruder die and the quenching bath is short and the fiber freezes before breaking up, whereas in Fig. 7.18(c) the distance was increased, giving the filaments sufficient time for breakup. As the filament extends, its diameter is reduced until shear forces no longer dominate the surface tension cohesive forces and the filaments breaks into droplets, just like a stream of water from a faucet breaks up into droplets.

This is the simplest model of a melt extruder-die system, but it qualitatively represents the behavior of any melt extruder-die combination, and it even provides good order of magnitude for them. 

Ram extrusion is a process to produce PTFE extrudates of continuous lengths. Granulated resins used in ram extrusion must have good flow characteristics so they can be fed readily to the extruder die tube. Presintered and agglomerated PTFE powders with bulk density ranging typically from 675 to 725 g/1 are used for this process.5... 

An extruder die s orifice is usually made oversize to the shape and size of the required contour. The final shape develops downstream from the die as the plastic expands, warps and/or shrinks. The best designs are based on past experience with a particular profile shape. As usual experience or being trained by one with experience has always been a real plus. 

There is off-line (for small quantity of products) or in-line postforming. The in-line refers to forming/shaping the extrudate (tube sheet, etc.) just after it emerges from the extruder die but before the plastic has a chance to cool. It provides specialty products with performance and cost advantages. Upon leaving the extruder s die and... 

Seat (or breaker plate Ring for attachment extruder Die lend... 

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