Scale blending

Figure 18-21 gives some data on the circulation time of the hehcal impeller. It has oeen observed that it takes about three circulation times to get one blend time being the visual uniformity of a dye added to the material. This is a macro-scale blending definition. 

Eigure 6 shows the stiffness of Ecoflex /PLA blends depending on the PLA amount. PLA today is a thermoplastic polymer made from renewable raw materials and is available on industrial scale. Blending the completely different thermoplastic polyesters - stiff and brittle PLA with soft and flexible Ecoflex - a whole range of different material properties can be accessed, depending on the ratio of both polymers. 

The scientist seeking to scale blending processes must be well aware of the limitations of the state of science in this area. Equal consideration must be given to the state of the blend in the blender, as well as the effects of subsequent handling. 

Blending is performed most frequently by two methods bottle or jar blending and motorized blenders. Neither technique has a clear advantage over the other. The bottle process is suitable for modest scale manufacturing. Large scale blending is usually done in a V-cone blender (see Fig. 5.27) such as the units offered by Patterson-Kelley Corporation, East Stroudsburg, Pennsylvania, USA. 

The pilot-scale blending tank has an internal diameter of 2 m and a height of 3 m. Inlet fiow rate wi and inlet composition X2 are constant. The nominal steady-state operating conditions are as follows ... 

FTIR and other analyses confirmed the existence of intermolecular hydrogen bonding between PBI and PA the carbonyl band shifts from 1741 to 1730 cm in an 80/20 blend. Also, miscibility and compatibility were indicated further by the clarity (visual and microscopic examination) of films prepared from the 80/20 blend TGAs showed blends conforming to the Rule of Mixtures, and X-ray diffraction (XRD) analysis confirmed that PBI and PA interact and are compatible on a molecular scale blends were found to have physical properties adhering to the Rule of Mixtures values the thermal stability of the blends at 550°C increased proportionately as the relative PBI concentration increased and after blending, the hydrophilicity of the PBI decreased dramatically. Thus, PAs and aromatic PBIs were found to be miscible in all proportions, and synergistic effects of one polymer over the other s weak properties can be achieved. 

A new mixer, the Minibatch mixer, has been developed for small-scale blending of specialty polymers and nanoscale composites. This mixer is a 1 20 scale down of the standard 60mL internal batch mixer and maintains general geometric similarity. Morphology of immiscible blends showed a spherical dispersed phase stracture and uniform distribution throughout the blend however, particle size of blends made in the Minibatch appeared... 

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