Polymer blend processing Most commercial polymer blends are produced by melt mixing in continuous compounding equipment such as single-screw or twin-screw extruders and kneader-extruders. Twin-screw extruders are becoming more popular because of their greater versatility and production effi ciency. Owing to their segmented barrel and screw designs, twinscrew extruders offer the advantage of multiple processing zones. The degree of shear mixing, residence time, and the temperature in each of these zones can be varied at will by simply changing the order and/or the type of the screw elements and kneading blocks, and using separately controlled heaters.