Speaker
Description
Thermoplastic starch, a group of starch-based materials, has often been under review because
it can be used as low-cost bioplastics. Native starch is usually processed under the action of
high temperature and shear stress with addition of plasticizers such as low molecular weight
polyols and/or amide-containing molecules to obtain a moldable thermoplastic material. Such
materials are sensitive to ageing and time dependent changes in their structure are of great
importance for the use of materials in practice. In this study, solid-state magic-angle spinning
1 H NMR was used to characterize structural changes in cornstarch plasticized with glycerol
and urea during one-year ageing. It was found that widths of the signals related to urea and
glycerol CH/CH 2 groups did not change significantly while widths of the signals coming from
water and glycerol OH groups decreased by about half after one year of storage. This could
mean that urea formed stable hydrogen bonds with starch which were not affected too much
during storage whereas hydrogen bonds between glycerol OH groups and urea were disrupted
which resulted in increased mobility of glycerol and perhaps also phase separation of glycerol
and water during ageing.
