Extrusion equipment design

The attributes of the extrudate, such as density, thickness, and moisture content, are controlled by variables due to the formulation, extrusion process, and equipment design. The properties of the wet feed material and its ability... 

Just in the USA during 2001, the man-made plastic fiber industry had over 90 plants with sales of 13 billion and employed about 45,000 people. Fabrication processes are diverse both in technology and equipment design. They have common steps that include preparation of reactants, polymerization, plastic recovery, plastic extrusion, and supporting operations. In some preparation operations, solvents are used to dissolve or dilute monomer and reactants. Solvents are also used to facilitate the transportation of the reaction mixture throughout the plant, to improve heat dissipation during the reaction, and to promote uniform mixing. Solvent selection is optimized to increase monomer... 

SBC can be processed on most conventional blow molding and injection blow molding equipment designed for many other types of polymers with little or no equipment modifications. This includes continuous, accumulator head, or reciprocating screw extrusion blow molding equipment. Bottles made from SBC have been used widely for applications such as honey bears. The SBC will withstand the moderate hot fill temperatures required for this application. 

Nucrel [DuPont]. TM for an ethylene-meth-acrylic acid copolymer resin available for use in conventional extrusion coating, coextrusion coating, and extrusion laminating equipment designed to process polyethylene resins. Higher melt flow index results in fewer resin leaks. 

The amount of lubricant in the compound depends on the type of product, equipment design, and the desired extrusion pressure. Its content should be as low as possible but not so low that the extrusion pressure would be excessively high. A less volatile extrusion aid is often recommended for the manufacture of an unsintered tape. The range of lubricant content is 15%-25% of the total weight of the compound. 

In general, all twin-screw extruder manufacturers have developed their own specific equipment design to increase the extrusion rate by increasing the free volume of each element and increasing the ability to withstand a high torque requirement. Three major developments are described in the following sub-sections. 

Similar injection-molding equipment design considerations apply to extrusion equipment such as long plasticating screws with 24/1 or higher L/Z) ratios and approximately 3 1 compression ratios. ... 

The book by Schenkel [2] is a translation of the German text Kunststoff Extruder-Technik [3], which is an extension of the original book Schneckenpressen fuer Kunststoffe [4]. This book is very complete dealing with flow properties of polymers, extrusion theory, and design of extrusion equipment. The emphasis of Schen-keTs book is on the mechanical or machinery aspects of extruders. As in Bernhardt s... 

In a correctly designed extruder, the majority of the wear should be concentrated on the screw because the screw can be replaced and rebuilt more easily than the barrel. In fact, the rebuilding of extruder screws has become so common that the rebuilding business has become a major segment of the extrusion industry. There are more than 70 companies in the U.S. involved in the rebuilding of extrusion equipment. For a number of these companies, screw rebuilding constitutes the major part of their business. 

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