An understanding of factors such as their rheological to decomposition behaviors as well as problems that can develop provide information that will make it easier to extrude products ( Chapters 1, 2, 3, and other chapters).Дownstream of the die, the extrudate (melt) is calibrated, cooled and packaged by an array of ancillary auxiliary devices including vacuum calibrators, water tanks, cooling rolls, haul-offs, cutters, and winders ( Chapter 18). In producing the different extruded products certain plastics can be used. In maximizing performance, or at least meeting performance requirements of extruded plastics as well as minimizing cost to extrude products it is important to understand the processing behavior of the different plastics. b These are strictly typical average values for a resin class consult your resin supplier for values and more accurate information. Section 7.9 provides detailed information about the rheology of fluoropolymers.ДЄ Specific information on all machine settings and plastic properties is initially acquired by using the resin supplier's data sheet on the oarticular compound or resin to be used. Typical symptoms of melt fracture include a rough surface ( shark skinning) and frosty or cloudy surface. Parts extruded in a process that exceeds the critical shear rate have poor quality. The critical shear rate of most fluoropolymers is usually much lower than most thermoplastics. Melt fracture in molten plastics takes place when the velocity of the resin in flow exceeds the critical velocity, the point where the melt strength of the polymer is surpassed by internal stresses. Fluoropolymers, and generally thermoplastic materials, must be processed below the velocity at which melt fracture occurs, referred to as the critical shear rate. Rheology of the molten fluoropolymers is of critical importance in the extrusion of these polymers. Chapter 10 provides information about the metals and their suppliers that are recommended for the construction of the various parts of fluoropolymer extruders. Corrosion of process surfaces can result in the contamination of the finished product and deterioration of its physical properties. These metals are significantly more expensive than lower grades of steel. It is important that the surfaces of machines that come in contact with molten fluoropolymers are constructed from special grades of corrosion-resistant metals. The products of degradation of molten fluoropolymers are highly corrosive, often containing hydrofluoric acid. Sheet and profile extrusions account for a small share of fluoropolymers consumption. Fluoropolymer films are widely used in release, surface protection, and packaging.

The principal end products are wire insulation, tubing, film, and sheet. Unlike injection molding, extrusion usually results in a semifinished or intermediate article that needs further processing to arrive at an end product.ДЇiber and filament accounts for a relatively small share of all fluoropolymers extrusion. Sina Ebnesajjad, in Fluoroplastics (Second Edition), 2015 11.1 IntroductionД®xtrusion is one of the most popular processes for fabricating parts from fluoropolymers.

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