Twin screw extrusion geometry

Continuous processing of filled elastomers by twin-screw extrusion and achievement of viable mixing distribution characteristics present formidable challenges. A thermoplastic elastomer, HyTemp, is plasticised with DOA and filled with ammonium perchlorate powder and additives. It is found that the extruder geometry, the order of ingredient addition and die pressmisation have profoimd effects on the mixing distribution characteristics of the elastomer-based extraded profiles. The mixing distribution characteristics are quantitatively determined by X-ray diffraction techniques. 16 refs. 

By far most of the PVC produced is then further processed by extrusion to make products such as pipes, plates, and profiles for the construction industry. Processing of PVC dryblends to make plasticizer-free hard PVC is done almost exclusively on counter-rotating twin-screw extruders, whereby the process engineering is geared to the specific material requirements. The chamber feed resulting from the screw geometry of the counter-rotating twin-screw extruder facilitates efficient plastifica-tion at precisely controlled temperatures — an important aspect for PVC [29]. 

Bhugra C, Shmeis R et al (2008) Prediction of onset of crystallization from experimental relaxation times. 11. Comparison between predicted and experimental onset times. J Pharm Sd 97 455 72 Booy M L (1978) Geometry of fidly wiped twin-screw equipment. Polym Eng Sci 18(12) 973-984 Breitenbach J (2002) Melt extrusion from process to drug delivery technology. Eur J Pharm Biopharm 54(2) 107-117... 

Starch can readily be modified by concurrent heat, application of moisture, and pressure. Such modifications may be conducted in extruders. Low moisture content favors formation of water-soluble starch with increased water-binding capacity, 65a 65e The solubility, water binding-capacity, and viscosity of gels prepared from extruded starch do not show linear relationships against either the moisture content in starch or the extrusion temperature.65c-65f Such extruder variables as the type of screw (either single or twin), pattern of the barrel and die heating, screw velocity, and geometry of the screw thread are also essential factors.65 ... 

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