The effects of different starch sources and plasticizers on film blowing of thermoplastic starch: Correlation among process, elongational properties and macromolecular structure

The material compositions and the technological procedures to prepare biodegradable films with the film
blowing technology based on thermoplastic starch were studied in this work. The activities were focused
on the analysis of the effects of starch source (maize, potato and wheat), supplier (Roquette, Cerestar and
Cameo) and the type of plasticizers (glycerol, urea and formamide) and their content on the physical-
chemical and mechanical properties. Moreover, in order to develop a film blowing technology, material
composition as well as processing condition were optimized. Among 10 varieties of thermoplastic starch
prepared, the combination of urea and formamide as plasticizer restrained retrogradation and improved
mechanical properties. Extensional rheological properties of the thermoplastic starch films were also
investigated: the results showed that the occurrence of strain-hardening behaviour in some of the investigated
compositions lead to a positive effect on the film blowing process. In this study we found that the
combination of high-amylose (>51%) starch and urea/formamide mixtures as plasticizer produced an
homogenous film of a 50 lm thickness and a robust film blowing process due to the good elongational
viscosity, high deformability of the melt and strain-hardening behaviour.