Mixer, pineapple

Figure 8.26 Schematic of two common knob-type mixers a) a straight knob mixer with the knobs in the same angular position, and b) a pineapple mixer with the knobs positioned in a spiral pattern in the same direction as the main flights of the screw channel...

Fig. 23. Screw sections for enhancing distributive mixing in single-screw extruders (a) Dul-madge mixer, (b) Saxton mixer, (c) pin mixer, (d) pineapple mixer, (e) cavity transfer mixer, (f) slotted screw flight, (g) Kenics and Ross ISG static mixers [148]...

This barrier screw appears similar to that in descrihed [13]. With screw pitch decreased within the feed zone, air cooling is sufficient to control the feed zone temperature. Shearing elements plus a pin/pineapple mixer follows the barrier melting zone. 

This causes a problem in choosing which mixer would be the best for a particular application. For example, a pineapple mixer has studs which may have some resemblance to a pineapple, but the studs may be square or diamond, large or small, be continuous like a chocolate bar or separated. 

Mixer J Figure 8.22 (bottom). A pineapple mixer [20] with 15 rows of studs axially and 12 rows of studs circumferentially (Figure 8.25). 

Mixer G and pineapple mixers were 170 watts and above. Melt temperatures followed similar trends to drive power except for Mixer G. Pressure drop with HDPE was neutral for the screw at the selected speed, but was +0.69 MPa for LDPE and -0.345 MPa, i.e., pressure generating, for PP. 

The Pineapple mixer with the many small studs mixed much better than the one... 

Overall, the TMR mixer produced the best results. The Pineapple mixer was better than the Maddock element. 

These trials were carried out using 5 95 wt% PS LDPE which had viscosity ratios of 34 at 180 °C and 45 at 160 °C. The apparatus comprised two separately extruded polymer streams feeding a barrel flighted plain mandrel screw evaluator [25] fitted with a pineapple mixer. The overall arrangement was similar to that described in Section 8.6. The blends were also prepared with 0.5 wt% Kraton compatibiliser precompounded into the PS. To facilitate comparison of the results in their graphs, those for 30 and 90 rpm are presented in Table 14.2. 

Table 14.2 Polymer blending results using a flighted barrel/plain mandrel screw evaluator fitted with a Pineapple mixer ...

The results show that small particles are produced with viscosity ratios of up to 45. The influence of rotational speed is also of interest, showing a similarity to the mixer evaluation trials in Section 8.5.3, noting also that in this evaluation the pineapple mixers had an average to poor mixing performance compared with other devices. The presence of Kraton compatibiliser promoted formation of a slightly smaller droplet size. 

With the mixer on low speed, alternate adding the flour mixture and the pureed pineapple, starting and ending with the flour. Use a rubber spatula to scrape the batter over the gooey topping in the skillet. 

Foam mat drying, originally developed by Morgan, involves drying thin layers of stabilized foam from liquid food concentrates in heated air at atmospheric pressure. Foam is prepared by the addition of a stabilizer and a gas to the liquid food in a continuous mixer. It can be dried in a continuous belt-tray dryer. Good quality powders capable of instant rehydration were made experimentally from tomatoes, oranges, grapes, apples, and pineapples [22]. 

The pretreated pineapple fibers were mixed with the PP in a thermokinetic mixer with speed rate maintained at 5250 rpm, in which fibers were responsible for 5 wt% in the composition. After the mixture, composites were dried and groxmd in a mill. The composites were placed in an injector camera at 165°C and 2°C min heating rate in a required dimension pre-warm mold with specific dimensions for impact specimens. 

As an extension to the above study, several types of dispersive and distributive mixing elements (26) were evaluated using a single-screw extruder (27) compared with the Maddock mixing element used in the previous study. Elements evaluated included dispersive elements such as straight and tapered Maddock, pineapple and Twente mixers, and distributive elements such as pin and gear... 

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