Barrel temperature profile

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. 

In setting up the barrel temperature profile start with the front to rear zones (die end to feed section). The heat controllers are set slightly above the plastic melting point prior to turning on the heaters. Heat-up should be gradual from the ends to the center of the barrel to prevent pressure buildup from possible melt degradation. With this startup follow through with ... 

Extrusion conditions feed rate, 800 g min", screw speed, 300 rpm twn Aes, 4 mm diameter, barrel temperature profile, 25/55/120/150/150°C from feed port to die. From Guy and Home (1988) with permission. 

Barrel temperature profiles were used as the set points in the process since it was not possible to set the melt point. The resulting melt temperatures were recorded at each setting. Coolant temperature settings were used to control mold temperature. Pack and hold pressures were paired and represented as a single independent variable. Resulting melt pressure at the nozzle was estimated using the intensification ratio of the press. 

The neat PP and PP-g-MAH were dried in a vacuum oven at 80°C for 6 hours. Melt extrusion technique was applied to produce different compositions of PP/ nano-CaC03 by a ZSK-25 (Coperion Werner Pfliederer-Germany) co-rotating twin-screw extruder (D= 25 mm, L/D = 40) with a barrel temperature profile ranging from 160°C near the hopper to 200°C at the die and a screw speed of 400 rpm. 

Transparency Cloudiness or haze for clear plastics [contamination] /moist feed/ jmelt too cold] /faulty adjustment of barrel temperature profile/injection pressure too low/back pressure too low/[mold too cold]. Bubbles in dear plastics moist feed/ melt too hot] /injection pressure too low/injection rate too fast/injection hold time too short/booster time too low/[mold too cold] /mold cooling time too short/jcooled too fast]. ... 

Process variables barrel temperature profiles, screw speed, and feed rate. 

The barrel temperature needs to be measured to provide information on the axial barrel temperature profile and to provide a signal for the controllers of the barrel heaters and cooling devices. The temperature should be measured as close as possible to the inner barrel surface, since the polymer temperature is the primary concern. The worst possible location of the temperature sensor would be in the barrel heater itself. However, there are some commercial extruders where the temperature sensor is placed in the barrel heater to reduce the thermal lag of the system. The major drawback of this approach is that one controls the heater temperature and not the temperature of the polymer in the extruder barrel. Some extruders are equipped with a combination of deep-well and shallow-well temperature sensors to improve... 

In these studies, it was found that significant meit temperature variations occur, as much as 45°C over 5 to 10 seconds. Figure 8.109 shows these melt temperature variations for three screw geometries at three barrel temperature profiles and at two screw speeds. 

High melt temperature variations do not necessarily result in large pressure fluctuations. This is evident in Fig. 8.110 where the melt pressure variation is shown for the same three screws at the same screw speeds and barrel temperature profiles. 

The 220 barrel temperature refers to the temperature of the last barrel temperature zone the actual profile is 150-185-205-220. For the 200 barrel temperature the actual profile is 140-170-185-200 and for the 180 barrel temperature the actual profile is 130-155-165-180. For the simple conveying screws, the barrel temperature profile (BTP) has little efi ect on the pressure variation, and the pressure variation is quite small. For the barrier screw, the BTP has a significant effect on the pressure variation and the pressure variation is much higher-as much as an order of magnitude. 

The MW results for the Maddock screw, general-purpose screw, and barrier screw do not differ markedly for each barrel temperature profile, the CRD screw achieved the best MW results, resulting in the highest MW values. In all trials with the CRD screw the MW values were above the specification limit. As a result, this screw was selected for the production process. Figure 8.115 shows a photograph of a slotted CRD mixer. 

Replaced temperature sensor in water line, 03-16-00 Changed barrel temperature profile, 04-12-00... 

The extruder barrel temperature profile remains the same... 

Processing temperature is one of the most important variables in the extrusion foaming process because it affects both the melt viscosity and the amount of gas given off upon the thermal decomposition of CFA [81-83]. However, high processing temperatures should be avoided due to the thermal instability of PLA. Similarly, lower melt temperature should not be used to prevent partial decomposition of the CFA. The extruder barrel temperature profile should be set up based on the melting temperature of the polymer and the decomposition temperature of CFA [86]. 

Figure 7.7 shows comparisons of sections taken from the final turn of the extruder screw (no.24) for (a) increasing, (b) constant, and (c) decreasing temperature profile with LDPE. Reversing the barrel temperature profile so that the feed end of the screw was at the highest temperature produced the highest output rate and the best mixing. 

Table 7.1 Influence of barrel temperature profile on output rate with and without a Maddock element...

Table 8.13. Recommended Extruder Barrel Temperature Profile and Screw Speed for Various Resins ...

Screw configuration S3 was chosen to examine how feed rate and screw speed may affect the morphology development of the reactive blend. In order to better reveal the effects of these two processing variables, the barrel temperature profile was voluntarily chosen as follows 220 °C for the first part of the extruder between the hopper and port 1 and 240 °C for the remaining extruder length. Table 6.5 shows the particle sizes of the PA6 phase along the screw axis at three different locations (port 1, port 2 and die exit) for four different combinations of feed rate and screw speed. The corresponding torque values of the screw shafts are also listed. 

S4 was used to process the PP/PP-g-MA/PA (80-X/X/20) reactive blend in the presence of varying amount of PP-g-MA denoted as X. The barrel temperature profile was set at 240 °C for the entire extruder. Figure 6.16(a) shows the PA6 number average particle size along the screw axis for four different PP-g-MA contents 1,5,10 and 20% by weight. The morphology development had been accomplished after the melting zone, except for the... 

Single-screw extmsion of rigid PVC definitely requires the use of a process aid to achieve optimum quality and production rates. Typically, 1.5-3.0 phr is sufficient. While not absolutely necessary in low-shear, twin-screw extmsion, the inclusion of at least 1.0-1.5 phr of a process aid definitely enhances product quality. Because of its effect on promoting powder fusion, a slightly lower barrel temperature profile may be used when running with a compound containing process aid on a twin-screw extrader. 

The two resins were run on the standard two-piece feedbloek and barrel configiu-ation. The feedblock was water-eooled. Onee these trials were completed the barrel and feedblock were changed to the single piece barrel with integral feedport. The same hump barrel temperature profiles were used for same barrel type and resin tested along with the same feed throat water temperature. See Chart 1 for barrel temperature profiles. 

Modified barrel temperature profiles may be needed to improve the overall melt tenq)erature of the process, which was not evaluated in this study. 

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