Improving tensile toughness of poly(lactic acid) and castor oil derivatives eco-blends via morphological regulation

Poly(lactic acid) (PLA) has attracted much attention and shows promising applications in numerous fields. In this study, PLA was plasticized using bio-based castor oil derivatives - hydrogenated castor oil (HCO) and castor oil glycidyl ether (COGE). These eco-blends were measured using a Fourier transform infrared spectrometer, a scanning electron microscope, a contact angle test, rheology, a differential scanning calorimeter, thermogravimetry, polarized optical microscopy, and a tensile test, respectively. The findings show that a core-shell morphology of COGE-HCO encapsulation is formed in PLA matrix, and the hydrogen bonding interaction and ring-opening chemical reaction among functional groups of the components greatly improve the compatibility, ductility, cold crystallization ability, and thermostability of the eco-blends, but the melt crystallization ability is hindered. The incorporation of HCO improves the hydrophobicity and oleophobicity of the eco-blends. Due to the combined effect of HCO and COGE, the melt viscosity reduces, and the Newtonian behavior enhances; the nucleation density and spherulitic growth of PLA increase. The strain at break of the PLA/HCO/COGE (90/7.5/2.5) blend reached 221%, which is 22.6 times higher than that of the neat PLA. These eco-blends present appropriate rheological, thermal, and mechanical properties, showing application scenarios in biodegradable packaging and disposable appliances.