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Film properties of hydroxypropyl starch

: Vorwerg, W.; Dijksterhuis, J.; Borghuis, J.; Radosta, S.; Kröger, A.


Starch = Stärke 56 (2004), Nr.7, S.297-306
ISSN: 0038-9056
Fraunhofer IAP ()

The present study describes the preparation of low-substituted hydroxypropyl (HP) starches and investigation of their suitability for the development of flexible, highly transparent cast films. Changes in molecular composition due to processing conditions were identified by determining molar mass distribution. Molecular characterisation was performed both by static light scattering (SLS) and size-exclusion chromatography with multi-angle laser light scattering (SEC-MALLS) detection. The weight-average molar mass, mean square radius of gyration, second virial coefficient, and molar mass distribution were determined. Rheological characterisation of concentrated aqueous solutions included a study of flow behaviour as a function of shear rate and oscillatory measurement of viscoelastic properties. Significant differences in rheological properties due to hydroxypropylation conditions were established. Mechanical testing was carried out by measuring tensile strength and elongation and determining the elastic modulus. The tensile strength of cast films based on hydroxypropyl starches was 40-50 MPa. Elongation values were dependent on the type of starch, use of plasticiser and storage conditions.