Process technology extrusion

Composites of polyhydroxy butyrate, a natural biodegradable thermoplastic P-hydroxy add, with TCP have been prepared by conventional melt processing technologies (extrusion, injection, or compression molding) [2, 17, 18]. In vitro experiments in SBF produced an apatite like stmcture on the composite surface suggesting bioactivity. When immersion in SBF was extended to 2 months or more, the onset of matrix degradation could be followed by the decrease in storage modulus. 

Whereas all conventional thermoplastic fabrication techniques have been successfully employed to convert pellets of HIPS into useful articles, extrusion (film, sheet, profile and multi-layer) and injection molding (solid, structural foam and gas-assist) are the predominant processing technologies. Innovative hardware technologies, in both extrusion and injection molding, have provided means to combine less expensive materials, such as polystyrene, with polymers or structures offering key performance characteristics. 

The particular case of polymer-oligomeric compositions creates new technological possibilities such as the preparation of foamed articles directly at the place of utilization by foaming solutions or pastes at room temperature or sl tly elevated temperatures. It als) leads to a considerable reduction of enei consumption as cOTii ed to traditional processing methods (extrusion, casting and pressing). 

Biodegradable thermoplastics, like PHB and PLA, can be processed by conventional thermoplastic processing technologies, such as extrusion, injection molding, melt spinning, blowing film, and melt blown, for a wide range of application as enviromnentally friendly materials and for medical applications. 

The acceptability of polymer materials for processing by extrusion technologies is determined not only by their melt viscosity but also, largely, by viscoelastic properties. Such materials are characterized, first of all, by strength and swelling of the melt jet (74,77). 

The ability to be integrated in polymer processing techniques (extrusion, injection...) or composite technologies. 

There are only a few technologies that in the process of their development have found such an extensive range of appUcation as that of extrusion technology. Its origin was in structural ceramics, yet nowadays the extruder is employed in such diverse industries as the plastics industry, the chemical and its related industries, foodstuffs industry, fodder concentrate industry, etc., both for extrusion as well as for preparation and other process technologies. 

Most of the processes are well scalable although, sometimes technical issues—such as mechanical capabilities, control, or hazard control—have to be overcome. When it comes to scale, vibrational laminar flow break-up processes are the predominant technology in terms of flexibility, capacity, and costs. However, the process technology is not yet as far advanced as much older technologies as extrusion or spray drying, where basic knowledge about the processes can be assumed with any... 

Various conventional processing technologies, such as casting, extrusion, injection and compression moulding, have been adapted for processing starch-based materials, as well as some new techniques, such as orientation and reactive extrusion. 

The technological challenge for the material is to on one hand achieve the necessary material properties like electrical conductivity and on the other hand have sufficient flow characteristics which allows for processing by extrusion, compression molding, and injection molding. 

Schott, N. R., Plastics Extrusion Processing Technology Seminar, University of Lowell, 1988. 

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