The physical properties of poly(l-lactide) and functionalized eggshell powder composites

Aiming at improved crystallization performance and simultaneously enhanced solid-state properties of poly(l-lactide) such as mechanical properties and enzymatic hydrolysis. A novel functionalized eggshell powder decorated with calcium phenylphosphonic acid (NES) was synthesized via the chemical reaction between phenylphosphonic acid and calcium ion on the surface of eggshell powder to form effective nucleating surface for poly(l-lactide). The resultant NES was incorporated into PLLA matrix to form fully biodegradable composites by melt blending, which exhibited superior crystallization, mechanical properties, and enzymatic hydrolysis. Upon the addition of 20 wt% NES, the crystallization half-time of a PLLA/NES composite decreased from 27.09 to 0.69 min at 130 °C, compared to that of neat PLLA. The storage and tensile moduli of the composites increased with increasing NES loadings. Even with 20 wt% NES, the composite still exhibited good mechanical properties with tensile strength of 53.4 MPa, tensile modulus of 2460 MPa and elongation at break of 2.5%, respectively. Moreover, it was interesting to find that the enzymatic hydrolytic degradation rates had been enhanced pronouncedly in the PLLA/NES composites than in neat PLLA. Such high performance biocomposites have great potential in expanding the utilization of eggshell powder from sustainable resources and practical application as PLLA-based bioplastic.