Phase Morphology, Mechanical, and Thermal Properties of Calcium Carbonate-Reinforced Poly(L-lactide)--poly(ethylene glycol)--poly(L-lactide) Bioplastics.

Poly(L-lactide) (PLLA) is a promising candidate as a bioplastic because of its non-toxicity and biodegradability. However, the low flexibility of PLLA limits its use in many applications. Poly(L-lactide)--poly(ethylene glycol)--poly(L-lactide) (PLLA--PEG--PLLA) block copolymer is of interest for bioplastic applications due to its superior flexibility compared to PLLA. The aim of this work is to modify PLLA--PEG--PLLA using a low-cost calcium carbonate (CaCO) filler to improve material properties compared to PLLA/CaCO composites. The addition of CaCO enhanced the crystallinity and thermal stability for the PLLA--PEG--PLLA matrix but not for the PLLA matrix, as determined by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and thermogravimetric analysis (TGA). Phase morphology investigation using scanning electron microscopy (SEM) revealed that the interfacial adhesion between PLLA--PEG--PLLA and CaCO was stronger than between PLLA and CaCO. Additionally, tensile testing was carried out to determine the mechanical properties of the composites. With the addition of CaCO, the tensile stress and Young's modulus of the PLLA--PEG--PLLA matrix were increased, whereas these properties of the PLLA matrix were significantly decreased. Thus, CaCO shows great promise as an inexpensive filler that can induce nucleation and reinforcing effects for PLLA--PEG--PLLA bioplastics.