This thesis reviews the theory of isothermal melt extrusion beginning with the writings of early researchers up to its present state. The isothermal extrusion of a near-Newtonian liquid is compared to polyethylene, using five different extrusion screws, and calculated discharge rates are compared to the actual rates for both materials. A method of calculating forward flow was developed and this was shown to provide very good correlation with actual dis-charge rates.
Non-isothermal or plasticating extrusion of polyethylene was also studied and comparison is made to isothermal melt extrusion. The results obtained with the various types of screws studied are also discussed
