Cooling thermoforming

Sheet Extrusion and Thermoforming. Sheet for thermoforming and analogous operations is usually formed by extmding the melt through a slot die onto a set of poHshed chill roUs. The sheet is usually approximately 150 cm wide. After rapid cooling, the web is coiled or cut into sheets. Polystyrene, PVC, polyethylene, polypropylene, and filled polypropylene are prepared in sheet form by extmsion. 

This work was motivated by cracking of a thermoformed part while cooling on the mold, the complexity of the problem could be immediately appreciated since the effect was sensitive to very delicate changes in material composition. Due to coupling between the heat transfer and stress evolution, both problems were solved simultaneously ... 

During the thermoforming process (see Fig. 12), the sheet is heated above the glass transition temperature and below the melting point of the crystalline phase [35]. Afterwards, the hot sheet is formed into a chilled mold using vacuum, pressure and/or mechanical force. After a cooling step, the thermoformed containers are punched out and ejected. The skeleton (30-70% of the total volume) is recycled in the same application (Fig. 12). 

Thermoforming station (pocket depth, pocket rupture) Forming head pressure and pressure distribution Cooling water supply for heated and cooled tools Vacuum exhaust system Empty hopper detector Fill control system... 

Extruded articles Mater-Bi can be extruded and rolled with water cooling. For example, it is possible to produce completely biodegradable cotton buds of Mater-Bi on traditional extrusion lines. Other examples include extruded nets for fruit and vegetables and sheets for thermoforming. 

Thermoforming is a process in which extruded sheets are converted to articles by heating above their softening point, forming the softened sheet in a mold and allowing the formed sheet to cool and harden. The typical MFR range for such products is from 1 to 5dgmin 1, typical applications are... 

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