Rauwendaal Polymer Extrusion Pdf Download [NEW]
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Initially published "to bridge the gap between theory and practice in extrusion", this 4th edition of Polymer Extrusion continues to serve the practicing polymer engineer and chemist, providing the theoretical and the practical tools for successful extrusion operations. In its completely revised form, it also incorporates the many new developments in extrusion theory and machinery over the last 15 years.
We have several copies $35.00 still available call 530-269-1082 or email firstname.lastname@example.org! Available from Rauwendaal Extrusion Engineering, Inc. Written in 1988 for Dr. Rauwendaal's PhD Thesis. This dissertation deals with various theoretical and experimental aspects of leakage flow of polymer melts in the flight clearance of screw extruders. A special leakage flow test (LFT) apparatus was developed to measure leakage flow over a flight. Experiments were also performed on a 38-mm single screw extruder with various polymers. A detailed theoretical analysis of melt conveying in screw extruders including leakage flow was developed; both analytical and numerical analyses are presented. The implications of this research is discussed in detail, specifically issues related to wear problems caused by metal-to-metal contact between screw and barrel.
Abstract:A review paper is presented on modeling for polymer extrusion for both single screw and twin-screw extrusion. An issue of global modeling is discussed, which includes modeling for solid conveying, melting, melt flow, and co-operation of the screw/die system. The classical approach to global modeling of the extrusion process, which is based on separate models for each section of the screw, i.e., solid transport section, melting and pre-melting sections, and the melt flow section is presented. In this case, the global model consists of the elementary models. A novel continuous concept of global modeling based on CFD (Computational Fluids Dynamics) computations is also presented, and a concept of using the DEM (Discrete Element Method) computation coupled with CFD computations is discussed.Keywords: polymers; extrusion; modeling
There are two types of extruders: single and twin screw extruders (see Figure 2). Single screw extruders are primarily used for melting and conveying polymers to extrude them into continuous shapes whereas twin screw extruders are used for melt-mixing polymers with additional materials (pigments, fillers, reinforcers, and APIs), and for devolatilization. In the production of pharmaceutical formulations, which require homogeneous and consistent mixing of multiple formulation ingredients, a twin screw extruder is preferred because the rotation of the inter-meshing screws provides better mixing to produce a homogeneous solid containing finely dispersed API particles or a solid-solution of API in polymer. Consistent melt-mixing via twin screw extrusion can improve the dissolution rate and bioavailability of poorly water-soluble API formulations. Uniformly distributed API is also a prerequisite to produce drug-eluting devices with intra- and inter-batch reproducibility of drug-release kinetics.
As with any dosage form, material selection is critical in the development of a successful product. For most applications, the polymer should be thermoplastic, stable at the temperatures used in the process, and chemically compatible with the API during extrusion. For solid oral dosage forms, water soluble polymers are usually chosen from among well-known polymers already used in pharmaceutical products such as poly(ethylene glycol) and poly(vinylpyrrolidinone). With the increased interest in using HME for pharmaceutical products, major polymer suppliers are also beginning to offer polymers specifically designed for pharmaceutical applications. For drug-eluting devices, the polymers are generally water-insoluble, with most products under development using either ethylene vinyl acetate copolymers (EVAs) or polyurethanes. 2b1af7f3a8