Contiguous solids melting

In fact, in several extruders, dispersed solids melting (DS) is more likely to occur than contiguous solids melting. This is particularly true of extruders that do not feature a continuous, uninterrupted channel for material flow. Examples are twin screw extruders and pin barrel extruders. 

Fair melting contiguous solids melting mechanism... 

Fig. 37. Contiguous solids melting in single screw extruders.

The simplest form of melt extmsion is the use of a slot die to form the molten polymer into a thin flat profile which is then quenched immediately to a solid state (Fig. 1). This is usually done by contacting the hot web very quickly on a chilled roU or dmm. A liquid quenching bath may be used ia place of or contiguous to the chill roU. Depending on the polymer type or formulation, the quenched web is generally substantially amorphous. In some cases, the web may be drawn down ia thickness by overdriving the quenching roU relative to the extmsion velocity. 

As mentioned earlier, the CSM type melting is the one that has been most often observed in single screw extruders. However, in some experimental studies it was found that the solid particles are not contiguous but dispersed in a melt matrix [256-258] as illustrated in Fig. 7.47. 

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