Polymer melting shear heating

The unit can be fed polymer in the particulate solids form or as strips, as in the case of rubber extrusion. The solids (usually in pellet or powder form) in the hopper flow by gravity into the screw channel, where they are conveyed through the solids conveying section. They are compressed by a drag-induced mechanism in the transition section. In other words, melting is accomplished by heat transfer from the heated barrel surface and by mechanical shear heating. 

Heating and cooling often take place while the polymer melt flows, making viscous dissipation an influencing factor during the process. However, since most plastic parts are thin, the conduction often occurs only across the thickness and the viscous heating is a result of shear within the narrow gap of a die or mold cavity. For such cases, the equations reduce to,... 

H. T. Kim and E. A. Collins, Temperature Profiles of Polymer Melts in Tube Flow. Conduction and Shear Heating Corrections, Polym. Eng. Sci., 11, 83 (1971). 

During the plastication stage, the polymer melt is typically plasticized from solid granules or pellets through the combined effect of heat conduction from the heated barrel and the internal shear heating caused by molecular deformation with the rotation of an internal screw. Screws in injection molding have many... 

Formulas and Data Sheets, issued yearly, containing all newly established fundamental equations and numerical data on basic properties of polymers. These would include new equations to express viscosity as a function of temperature, concentration, or shear rate new relations between intrinsic viscosity and molecular weight new formulas on the kinetics of polymerization and copolymerization data on second-order transition points of new polymers or copolymers heat and entropy of solution, dilution, melting, and swelling of macromolecules and similar fundamental data as they are contained in the articles appearing during the reference year. They would be similar in purpose to the Technical Data Sheets and complement them in regard to fundamental information. 

Melt Processible Polymer - A polymer that melts when heated to its melting point and forms a molten material with definite viscosity value at or somewhat above its melting temperature. Such a melt should be pumpable and flow when subjected to shear rate using commercial processing equipment such as extruders and molding machines. 

---