AbstractA combination of theoretical and experimental studies have been carried out to investigate the mechanisms of heat transfer during the rotational moulding process for plastics. A computer simulation was developed in order that a fundamental understanding of the interaction between biaxial motion, powder properties, mould materials and forced convective heating could be obtained. Temperature measurements were made during moulding trials using an insulated datalogging device to verify the findings of the computer simulation.
These measurements were found to maintain a consistent form, regardless of mould material and thickness, oven temperature or polymer material and thickness. It has been established that changes in the internal air temperature can be used to pin-point when all the material has adhered to the mould and when all the material has subsequently crystallised.
Optimum properties of medium density polyethylene were measured for changes in moulding parameters and correlated with maximum temperatures achieved inside a part during moulding. Degradation of the inner surface of a part has a critical effect on its final service performance. The moulding and testing trials have shown that this can be avoided by ensuring that the temperature inside the wall of a part does not rise above 200°C (MDPE).
Finally, a device has been developed to allow the real time measurement of temperatures inside a mould during processing. Signals transmitted from a remote device within the oven permit true process control for rotational moulding to become a reality for the first time.
|Date of Award||Dec 1990|
|Supervisor||R.J. Crawford (Supervisor)|