Polymer Extrusion (ePub)

Extrusion is by far the most important and the oldest processing
and shaping method for thermoplastic polymers. This process
concerns almost all synthetic polymers, as well as elastomers or
food materials. Single-screw extrusion is mainly used
nowadays to manufacture finished goods or semi-finished products.
More than 90 million tons of thermoplastics are therefore processed
every year.

Twin-screw extrusion may be divided into two systems:
contra-rotating systems used within the context of PVC extrusion,
for the manufacture of pipes or profiles; and co-rotating systems
experiencing nowadays a very significant development, because of
their significant adaptability and flexibility, which enables the
manufacture of specific materials (polymer alloys, thermoplastic
elastomers, filled polymers, nanocomposites). Extrusion is carried
out by passing molten polymer through a tool called die that will
give the product its final shape (films and sheets, rolled
products, and electric cables). Thanks to the design of dies, we
obtain at the output a product with controlled dimensions, uniform
speeds and homogeneous temperatures. The book will discuss the same
production types, but only in the case of coextrusion flows, i.e.
multilayer stratified products. First of all, we will present
in this book the physics of the mechanisms at stake, then propose
more or less complex models in order to describe these mechanisms
and then go forward in the interpretation of results and the
control of condition flows.