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Compounding of Particulate-Filled Thermoplastics

4

Peter Hornsby

Contents

Definition........................................................................................ 96

Scope of Compounding Requirements.......................................................... 96

Principles of Mixing with Filled Polymers..................................................... 98

Agglomerate Breakdown.................................................................... 99

Mechanism of Mixing....................................................................... 99

Rheology of Filled Polymers................................................................ 101

Constructional Features of Compounding Machinery for Filled Polymers.................... 101

Functional Stages............................................................................ 102

Premixing Processes......................................................................... 104

High-Intensity Melt Mixing Technologies.................................................. 105

Ancillary Compounding Equipment........................................................ 107

In-Process Compound Characterization..................................................... 108

Future Perspectives.............................................................................. 109

Further Reading................................................................................. 110

Abstract

The properties of filled thermoplastics critically depend on how the filler is presented in the polymer, especially its degree of interaction with the host matrix and the nature and extent of mixing achieved. Furthermore, the nature of the filler has a profound influence on the compounding methodology employed. Heat- and shear-sensitive fillers need a very different approach to fillers which have a strong tendency to agglomerate. Different technologies will also be required to produce highly loaded filled compounds to those containing small amounts of filler. The method used to combine filler and polymer defines the microstructure developed, principally through exposure to the shear and elongational flow fields encountered during melt compounding. This is influenced by the rheology of the

P Hornsby (*)

College of Engineering Mathematics and Physical Sciences, University of Exeter, Exeter, UK e-mail: This email address is being protected from spam bots, you need Javascript enabled to view it

© Springer International Publishing Switzerland 2017

R. Rothon (ed.), Fillers for Polymer Applications, Polymers and Polymeric Composites: A Reference Series, DOI 10.1007/978-3-319-28117-9_3

formulation and the constructional design and operational parameters used, which, in turn, define the extent and mode of mixing achieved. Additional functional stages may be required, for example, to extract volatiles from the compound or undertake reactive steps in the process. A key aspect in many filled compounding operations is the need for dedicated ancillary equipment, which often includes pre-blending components in the formulation, controlled feeding of filler and polymer into the compounder, and downstream cooling and pelletizing of the ultimate compound. In order to monitor compound consistency, a variety of in-process characterization techniques are being used or are under development. More energy-efficient filled compounding procedures are available which combine the mixing requirements with end product formation by extrusion or injection molding.

This entry will explore these issues, highlighting specific compounding requirements for differing filled polymer combinations, the principles of mixing particulate fillers into thermoplastic melts, and how this knowledge influences the engineering design and effective operation of industrial compounding plant.

Keywords

Mixing • Dispersion • Distribution • Rheology • Internal mixer • Ko-kneader • Twin-screw extruder • Mixture characterization

 
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