A new line is currently under testing at Union’s headquarters in San Vittore Olona (Milan) for the extrusion of foam PET sheet, for thermoforming and not just for it. The line consists of a drying system for raw material and a “loss in weight” type gravimetric dosing system.

Immediately downstream, two extruders in tandem, twin screw and single screw, guarantee a hourly production of over 300 kg/h with sheet width of 1100 mm and thickness adjustable from 1 to 4 mm. By changing the expanding gas quantity, weights ranging from 90 a 300 kg/m³ can be obtained.

The tandem solution developed by the manufacturer facilitates the achievement of the extrusion quality in particularly short times, even for a critical material such as PET, where temperatures can reach up to 280°C. The rheological study of the material made it possible to produce a circular die with which, although varying the thickness and density, it is not necessary to change dies. A new extruder cooling system keeps the temperatures at the set value, which is very important when using expanding gases to achieve a perfect cell formation.

A very important detail is also a cooling can specifically studied by Union to avoid any friction and obtain a top-quality sheet surface in terms of aesthetics and gloss. The integrated management software, also developed by the manufacturer, makes the process simple and reliable, from the formulation of raw materials to the winding of the finished product.