TPS Film-Blowing

Film-blowing is the most popular method of polymer processing, commonly used in manufacturing of packaging materials [1, 3], TPS is expected to be a promising raw material for biodegradable foUa, which can have enormous potential apphca-tion in that field too [2, 4, 5]. 

The TPS granulate was produced from different starchy raw materials (mixed with glycerol, partly enriched with emulsifiers), by use of a modified TS-45 extrusion-cooker and process conditions as described in Chapter 7. 

TPS film was produced by use of two screws of different geometries (compression ratios 2.0 and 3.5), and the screw rotational speeds were varied from 50 to 90rpm. The film was extruded with barrel and crosshead temperatures ranging from 70 to 155 °C. 

Thermoplastic Starch. Edited by Leon P.B.M. Janssen and Leszek Moscicki 2009 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-32528-3 

Addition of two emulsifiers-polyoxyethylenesorbitan monolaurate (Tween 20) and glycerol monostearate-at amounts of up to 2% considerably improved film flexibility. Moreover, it was found that damping of the mixture with only small amounts of water (2-5%) produced increases in film flexibility and strength. 

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Film blowing was accomplished with a compact extruder characterized by a 19 mm diameter and length of 25D. TPS can also be injection molded at barrel temperatures between 100°C and 180°C. 

Compounded TPS pellets can be blown into a film with 45 parts glycerol per 100 parts dry starch and 13 weight% moisture at a blow up ratio of 2-3 (Thumwall et al. 2008). 

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