Modelling of film casting manufacturing process longitudinal and transverse stretching

K e y w o r d s F i l m casting, Longitudinal stretching, Transverse stretching, Modelling industrial processes. 1. I N T R O D U C T I O N Film casting (Figure 1) is a widely used manufacturing process for polymeric films production; other processes are blow casting and extrusion, now generally used for the production of low quality films. A general overview of fihn casting and other analogous processes is given by Stoner [1] who also deals with manufacturing processes of different materials, as cellulose nitrate, polycarbonate , and polypropylene. An i m p o r t a n t advantage of film cas t ing with respect other similar processes is the relat ively faster and more uni form film cooling at the extrus ion die exit, and the possibi l i ty to work at relat ively higher t empera tu res , with good consequences on product ivi ty , film thickness, and optical properties. All above m a n u f a c t u r i n g processes make use of an ext ruder (with plane ext rus ion die in film casting). The raw mater ia l , i.e., polymer with oppor tune addit ives is in t roduced in the ext ruder which is cons t i tu ted by an empty cylinder in which a worm screw is placed (screw extruder) . Three different zones can be identified: an a l imen ta t ion zone, a t r ans i t ion zone, and a mater ia l meter ing zone. At worm screw end, polymer across a regula t ion valve used to ob ta in the required pressure increase. Then , a filter cons t i tu ted by a drilled plate is placed, mel ted polymer exit the extrusion die and the polymeric film is cooled by a roll at a constant temperature. 0 8 9 5 7 1 7 7 / 0 5 / $ see front matter @ 2005 Elsevier Ltd. All rights reserved. doi: 10.1016/j.mcm.2004.12.005 Typeset by A2MS-TEX 1326 P, CARLONE et al. I J Figure 1. Film casting process.