Modifications of Biodegradable Thermoplastic Starch (TPS) From Sago Starch via Cross-Linking Method

Introduction

Thermoplastic starch (TPS) is one of promising material to replace common synthetic polymer in packaging such as low density polyethylene (LDPE) and polypropylene (PP) sheets and film. Demand for starch is high in packaging applications due to the good tensile and gas barrier properties, and can be obtained from various renewable plant-based sources such as rice, potato, corn and sago. Starch in its native form is brittle and the hydrophilic nature of starch will results in poor moisture barrier properties and high water sensitivity of the starch-based film, as compared to synthetic polymer. Plasticizer such as glycerol and sorbitol are added into native starch to form TPS with improved flexibility and good barrier properties. However, TPS film will experience gradual loss in flexibility and its strength due to retrogradation which will affect quality of TPS, especially on its mechanical strength after storage period. Various chemical modification techniques have been developed to overcome these disadvantages. Chemical modification such as acid modification, cross-linking, esterification and etherification are among the options. This chapter will report on the current knowledge of TPS made from sago starch, pertaining to its properties with chemical modification via crosslinking.