After a brief introduction to the various types of polymers in use and the size and impact of the polymer processing industry, this overview focuses on the most important processes for thermoplastic materials, namely extrusion and injection moulding. Single and twin screw extruders are used for melting and pumping of polymers and for die extrusion for the production of lm, sheet, pipe, tubing, pro les and bres. Injection moulding is the process used for the production of numerous parts, small and large, by injecting a molten polymer into mould cavities. Various problems associated with these processes are discussed. Other processes described include: calendering, compression moulding, rotational moulding, powder injection moulding and thixomoulding. The overview concludes with a brief discussion of current trends and future challenges faced by the polymer industry.
MST/5866Dr Vlachopoulos (vlachopj@mcmaster.ca) is at the Centre for Advanced Polymer Processing and Design (CAPPA-D),
In this study, the finite element method was used to investigate the influence of screw speed, entering peroxide distribution, pressure‐to‐drag flow ratio, and channel geometry on the mixing characteristics of steady non‐isothermal reactive flows. The reaction considered was the peroxide‐initiated degradation of a polypropylene resin in the metering zone of a single‐screw extruder. The predicted average degree‐of‐freedom profiles from the simulations largely conformed to expectations. The average flow efficiencies for all runs were found to vary little along the channel length, remaining at values close to that for two‐dimensional flow. No significant effect of either screw speed or peroxide distribution was found on the flow efficiencies. However, both the pressure‐to‐drag flow ratio and the channel aspect ratio were found to have significant influences.
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