Effect of amphiphilic molecules on characteristics and tensile properties of thermoplastic starch and its blends with poly(lactic acid)

Three different types of amphiphilic molecules — Tween 60, linoleic acid, and zein were used as additives for the production of thermoplastic starch (TPS). The addition of those amphiphiles resulted in: (i) improved plasticization and processability, (ii) enhanced extensibility, (iii) increased crystallinity, and (iv) decreased stiffness, strength and rigidity of the TPS materials. Zein facilitated more effective plasticization, melting and processability of TPS material than did linoleic acid and Tween 60, respectively. However, Tween 60 allowed greater reduction of Tg and produced softer TPS material than did linoleic acid and zein, respectively. Binary blends of those TPS materials and poly(lactic acid) (PLA) were also fabricated by varying PLA content, i.e. 30, 50 and 70% (w/w). The melt flow index, tensile strength and elastic modulus of the TPF-PLA blends increased significantly with increasing PLA content. In addition, amphiphiles facilitated processability, flowability and extensibility of the blends. Linoleic acid was a more effective additive to enhance flowability of the TPS–PLA blends than were Tween 60 and zein, respectively.