Crystallisation behaviour and transparency of poly(lactic acid) nucleated with dimethylbenzylidene sorbitol

Abstract

In this paper, dimethylbenzylidene sorbitol (DMBS) was applied to poly(lactic acid) (PLA) as a nucleating and clarifying agents. Eight level concentrations, from 0.25 to 10 wt-%, were added and measured some changes in the thermal, mechanical, physical and morphological properties. Experimental results revealed that the nucleated PLA crystallised earlier together with the reductions of the crystallisation temperature (T_c) at all DMBS concentrations, while the glass transition temperature (T_g) reduced by around 10°C. The degree of crystallinity (X_c) increased from 1.48 to 16.6% corresponding to the decreased crystallisation time (t_c) from more than 40 to less than 5 min at 100°C. The nucleated PLA maintained its clarity at all DMBS concentrations, with reductions of the haze value from around 36–29%. The tensile modulus and tensile strength increased slightly with the content of DMBS up to 1.5 wt-%. Beyond this content, they dropped slightly.