Barrel temperature

The temperature of the melt downstream from the breaker plate may exceed the front barrel temperature, because of the mechanical work transmitted to the resin by the screw it varies with screw speed and flow rate. The melt temperature is measured by a thermocouple inserted into the melt downstream from the breaker plate. A hooded exhaust placed over the extmder die and feed hopper removes decomposition products when the extmdate is heated. 

Preforming. Extmsion preforming is easily accompHshed if relatively cool barrel temperatures are used with either a screw or piston type extmder (BarweU). It is important that the gums be used in the appropriate viscosity ranges, and that scorching be avoided. 

Extrusion. Extmsion techniques are used in the preparation of tubing, hose, O-ring cord, preforms and shaped gaskets. Typical extmsion conditions are 70 to 85°C for the barrel temperature and 95 to 110°C for the head temperature. The extmded forms are normally cured in a steam autoclave at 150 to 165°C. Some special grades of peroxide curable fluorocarbon elastomers can be hot air vulcanized. 

The injection moulding of melamine-formaldehyde moulding powders is now carried out on a small scale. Temperatures are somewhat higher than for U-F (e.g. barrel temperatures 100-115°C mould temperatures 163-177°C). Otherwise the considerations are the same as for the urea-formaldehyde compositions. 

The standard injection molding machine used had a screw diameter of 30 mm and the aspect ratio of 23.70. The barrel temperature profile was 270, 280, 290, and 295°C. The mold temperature was about 90°C. The injection molded tensile samples were processed according to the CAMPUS specification (Computer Aided Materials Preselection by Uniform Standards) [24] and DIN 53455 Form 3. To obtain the different flow conditions, four groups of samples were injection molded by varying melt... 

Most of the compounds were extrusion compounded in a conical, partially intermeshing, counter rotating twin screw extruder (Haake Reomix TW-lOO). The extruder speed was set at 50 rpm and the barrel temperature profile was set to produce a melt temperature of 260°C at the die. Samples were injection molded in a 31.8 MT Battenfeld press with a 59 cc shot size. Where noted, samples were compounded in a 60 cc Brabender internal mixer and compression molded. 

A schematic view of an extruder is shown in figure 1. The extruder barrel is essentially a ferrous alloy cylinder, with aluminum block heaters attached to the outside. There are several temperature control zones along the length of the extruder. Measurement thermocouples are installed in the extruder barrel itself. Barrel temperature is used to control the temperature of the polymer melt. Energy from the heaters is conducted both radially and axially in the barrel. Below, figure 2 shows a sketch of the extruder barrel, with the heaters and the temperature measurement points used in this paper marked. 

Calcium caseinate and butter oil have been extruded directly at 50-60% moisture levels to obtain a cheese analog with no surface water or fat (Cheftel et ah, 1992). The fat emulsification and melting ability increased with screw speed or barrel temperature. The texture of the extmded analogs was similar to those obtained by batch cooking and was affected by pH (Cheftel et ah, 1992) and emulsifying salts (Cavalier-Salou and Cheftel, 1991). The product can be used as adjimcts for hamburger, pizza, and sauces. 

Plunkett, A. and Ainsworth, P. (2007). The influence of barrel temperature and screw speed on the retention of L-ascorbic acid in an extruded rice based snack product. /. Food Eng. 78,1127-1133. 

In order to see if the system could provide the flexibility to evaluate high modulus polymer pellets, an initial comparison of an HDPE and PS resins were evaluated. The experiments were conducted at a screw speed of 50 rpm and barrel temperatures of 24 and 35 °C for the HDPE and PS resins, respectively. The temperature of the screw was maintained at the barrel temperature. These conditions are similar to what might be observed in the feed casing and very early into Section 2. As... 

Several of the most commonly used resins were studied at a screw and barrel temperature of 35 °C. As previously discussed, this temperature condition is comparable to the conditions in the feed casing or Section 1. This is just the start of solids conveying as conveying continues into Section 2 where the inside barrel wall temperatures are considerably higher. In order to visualize the contrast between the six different polymers tested, the solids conveying rates as a function of discharge pressure for these select resins are presented in Fig. 5.14. 

Figure 5.23 Solids conveying rate as a function of discharge pressure and barrel temperature for the shallow (8.89 mm) screw. The screw was maintained at a temperature of 50 °C and a speed of 50 rpm...

The effect of channel depth on solids conveying rate is shown in Fig. 5.26 for screw and barrel temperatures of 75 and 125 °C, respectively, and at a screw speed of 50 rpm. At zero discharge pressure, the solids conveying rates were nearly proportional to the depth of the screw channel (or cross-sectional area perpendicular to the flight). For example, the conveying rates were 91 and 125 kg/h for the 8.89 and 11.1 mm deep screws, respectively. For these screws, the cross-sectional areas perpendicular to the flights were calculated at 420 and 530 mm an area increase of... 

Figure 5.27 The effect of flight radii size on solids conveying rates for a barrel temperature of 75 °C, a screw temperature of 50 °C, and a screw speed of 50 rpm...

Womer, T. W., Wagner, J. R., Harrah, G., and Reber, D., An Experimental Investigation on the Influence of Barrel Temperatures on the Output of a Consfanf Depfh Screw wifh Grooved Barrel Feeding, SPE ANTEC Tech. Papers, 46, 259 (2000)... 

The melting process for a resin is complex and depends on many parameters, including screw speed, screw geometry, barrel temperatures, and channel pressures. Moreover, the compression ratio and compression rate also affect the pressure in the channel. The melting flux is known to increase with increasing pressure in the channel [1,12]. A series of Maddock solidification experiments were performed at... 

Figure 6.30 Photographs of the conventional melting of a commercial PP resin in an experimental extruder with a glass barrel. In both photographs a melt pool forms near the pushing side of the channel. The screw was rotated at 15 rpm and the barrel temperature was 90 °C. The ruler Is In Inches...

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