Page 105 - Academic Press Encyclopedia of Physical Science and Technology 3rd Polymer

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Encyclopedia of Physical Science and Technology EN012c-593 July 26, 2001 15:56

Polymer Processing

Donald G. Baird
Virginia Polytechnic Institute and State University

I. Introduction
II. Rheology of Polymer Melts
III. Thermal Physical Properties
IV. Extruders
V. Compounding
VI. Extrusion Dies
VII. Post-Die Processing
VIII. Molding and Forming

GLOSSARY Extrusion die A metal channel attached to the end of
an extruder to provide shape to an emerging polymer
Blow molding A polymer tube, referred to as a parison if stream.
extrudedandapreformifinjection molded,is expanded Film blowing An extrusion process for producing thin
into a cavity by means of air pressure where it is rapidly films of polymers with biaxial orientation based on ex-
solidified on contact with the mold walls. It is used for trudingfromanannulardieandsubjectingthebubbleto
producing hollow objects such as bottles, containers, bothaxial(drawing)andradial(airpressure)stretching.
and fuel tanks. Injection molding A cyclic automated process by which
Compounding The process by which other polymers and polymer pellets are melted in an extruder, the melt is
organic and inorganic additives are combined with a injected into a cavity, solidified, and the part removed.
polymer to improve processing performance and prop- The process is used to make small intricate parts as well
erties of the given polymer. as large parts for automobiles.
Compression molding A process by which a polymer Melt index The mass flow of a fluid (in grams) in the
mass is subjected to high mechanical pressure within period of 10 min from a capillary of known dimensions
a cavity to cause it to take the shape of the cavity, under a specified pressure and temperature.
solidified, and the part removed. Used primarily for Newtonian fluid A fluid in which the shear stress is lin-
highly filled polymers with a high viscosity and for early proportional to the velocity gradient; i.e., a fluid
highly filled thermosetting resins. of constant viscosity.
Extruder A device used to melt and pump polymeric Non-Newtonian fluid A fluid whose viscosity is not con-
fluids consisting of a screw rotating within a metallic stant and may exhibit a wide range of time-dependent
barrel. responses.

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