Enchanced extrusion with internal cooling die

by Chadalavada Bhaskar Rao

Institution: Ohio University
Department: Chemical Engineering (Engineering)
Degree: MS
Year: 1980
Keywords: Engineering, Chemical; Internal Cooling Die; Melt Conditioner; Polyethylene; polypropylene
Record ID: 1511416
Full text PDF: http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1181075895


The objective of this work was to design a biaxial die, with which extrusion could be done horizontally, thereby allowing better control of the temperature in the land and improvements in the operating con- ditions. The land temperature gradient was impressed previously by immersion of the exit end of the die under water. This improved design should be used with or without a melt conditioner. Polyethylene and polypropylene were extruded through a 12/1 (deformation ratio of 12 to 1) biaxial die, using a C.W. Brabender Model 200 Single Screw Extruder. The die was cooled with Teflon <sup>®</sup>to reduce friction between the walls of the die and polymer. The ribbons extruded were highly oriented and had high tensile properties and were 1.5 inches wide and 1/32 inches thick. Prestone <sup>®</sup>and water were used as coolant. For polypropylene the maximum extrusion rate of oriented ribbon was 9.2 inches per minute. Oriented polyethylene could not be produced successfully using this die. Thermal analysis of polypropylene samples demonstrated a 7.5° C melting point elevation and polyethylene samples demonstrated a max- imum of 3.5° C elevation in melting point. For polypropylene samples the maximum crystallinity obtained was 77.5%, maximum tensile strength was 67,840 Psi (0.468 G Pa). There were no changes in dimensions when kept in an oven at 100° C and at 140° C for a maximum of one hour. It was demonstrated that the horizontal extrusion can be done without producing surface defects and can enhance the orientation. The work suggests that the samples can be reproducible if the flow rate and temperature of the coolant are controlled.