Twin-screw extrusion mixing mechanisms

Fig. 10.12 Schematic representation of two melting mechanisms observed by Janssen (24) with PP processed in a double-flighted 47-mm counterrotating TSE operating at low rotational speeds, (a) Melting when the die pressure was set at the low value of 50 psi, where chamber-to-chamber leak pressure backflows are negligible, (b) Melting under the high die pressure of 2700 psi, which enables leak backflows, which result in chamber solid bed compaction and introduce the possibility of dissipative mix melting. [Reprinted by permission from L. P. B. M. Janssen, Twin Screw Extrusion, Elsevier Scientific, Amsterdam, 1978.]...

Kurokawa et al. [258-260] developed a novel but somewhat complex procedure for the preparation of PP/clay nanocomposites and studied some factors controlling mechanical properties of PP/clay mineral nanocomposites. This method consisted of the following three steps (1) a small amount of polymerizing polar monomer, diacetone acrylamide, was intercalated between clay mineral [hydrophobic hectorite (HC) and hydrophobic MMT clay] layers, surface of which was ion exchanged with quaternary ammonium cations, and then polymerized to expand the interlayer distance (2) polar maleic acid-grafted PP (m-PP), in addition was intercalated into the interlayer space to make a composite (master batch, MB) (3) the prepared MB was finally mixed with a conventional PP by melt twin-screw extrusion at 180°C and at a mixing rate of 160 rpm to prepare nanocomposite. Authors observed that the properties of the nanocomposite strongly dependent on the stiffness of clay mineral layer. Similar improvement of mechanical properties of the PP/clay/m-PP nanocomposites was observed by other researchers [50,261]. 

We have reviewed mixing mechanism, morphology development, and intermeshing co-rotating twin screw extrusion technology in the previous sections. For a given... 

The use of modified PTFE micropowder in combination with the mechanism of the controlled degradation of polyamide and the utilisation of melt-mixing devices like a lab melt mixer or twin-screw extruders are the basis of the reactive compa-tibilisation of the completely immiscible polymers. On the basis of the discussed mechanism PTFE polyamide block copolymers are formed by reactive extrusion ... 

A great deal of attention on PET/PEN blends has been paid to elucidate the type of kinetics of the transesterification reaction, and, in particular, reversible second-order kinetics has been found in solution [64], On the other hand, the reaction kinetics is strongly affected by terminal hydroxyl groups when the reaction is carried out in a mixing chamber [65], In the same device, studies on the thermal, rheological, and mechanical properties for blends with 25, 50, and 75 wt% of PEN content have also been reported [66], By using a twin-screw extruder, a block copolymer may be obtained via melt extrusion when the PEN content is 20 wt% [67],... 

Mohanty et al. [13] evaluated biocomposites formed using chopped hemp fibre and cellulose ester biodegradable plastic. The effect of two different processing approaches was studied. For the first process, the chopped fibre (30% by weight) was mechanically mixed in a kitchen mixer for 30 min followed by compression moulding using a picture-frame mould. The second process involved two steps first an extrusion process yielded pellets of cellulose acetate plastic (CAP) second, the pellets were fed into a twin-screw extruder while chopped hemp fibres were fed into the last zone of the extmder. 

CO-3-hydroxy valerate) (PHBV) and cellulose by extrusion blending, using a co-rotating twin screw extruder with a temperature profile ranging from 160 to 145 °C. PHBV pellets were dried, dry mixed with a cellulose nanowhisker powder and extruded. The extrudate was cooled in a water bath and the final pellets were dried. This material did not have the same mechanical properties and the same cellulose dispersion as the analogous composite prepared with solvent casting process. It was necessary to add a compatibilizer to improve the dispersion. 

Brouwer T, Todd DB et al (2002) Flow characteristics of screws and special mixing enhancers in a co-rotating twin screw extruder. Int Polym Process 17(l) 26-32 Carpenter J, Katayama D et al (2009) Measurement of Tg in lyophilized protein and protein exdpient mixtures by dynamic mechanical analysis. J Therm Anal Calorim 95 881-884 Chiang P-C, Ran Y et al (2012) Evaluation of drug load and polymer by using a 96-well plate vacuum dry system for amorphous solid dispersion drug delivery. AAPS Pharm Sci Tech 13(2) 713-722 Chokshi RJ, Sandhu HK et al (2005) Characterization of physico-mechanical properties of in-domethadn and polymers to assess their suitability for hot-melt extrusion process as a means to manufacture sohd dispersion/solution. J Pharm Sci 94(11) 2463-2474... 

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