Properties Investigation of Epoxidized Sunflower Oil as Bioplasticizer for Poly (Lactic Acid)

This study aims to improve low intrinsic ductility of poly (lactic acid) (PLA) by using a novel bio-sourced plasticizer environmentally friendly and cost-effective and to get a fully biodegradable material with potential application in films manufacturing. For that purpose, commercial sunflower oil (SO) was epoxidized and epoxidized sunflower oil (ESO) was used as plasticizer for PLA. To investigate ESO potential as plasticizer for PLA, its plasticizing effect was compared with commercial epoxidized soya bean oil (ESBO). Bioblends based on PLA and epoxidized vegetable oils (EVO) as bioplasticizers were prepared. The plasticizers (ESO or ESBO) were respectively compounded with PLA at 10, 20, 30, and 40 wt%. Mechanical (tensile and Shore D hardness), thermal (differential scanning calorimetry (DSC), thermogravimetric analysis (TGA)) and morphological properties (optical microscopy and scanning electron microscopy (SEM)) were characterized. The results showed that the addition of ESO or ESBO to PLA decreased tensile strength and tensile modulus compared to neat PLA but increased elongation at break for which an optimum (9 %, 16 and 34 % for ESBO, ESO5.5 % and ESO6.5 % respectively) was reached at a content of 20 wt% of plasticizer. The structures of the obtained plasticized PLA were confirmed by FTIR spectroscopy. The thermal properties (DSC), such as glass transition temperature (T-g) and melting temperature (T-m) were slightly decreased by addition of plasticizer into PLA, indicating that plasticizer increases the chain mobility and SEM analysis proved successful modification on the PLA brittle morphology with addition of EVO. On the other hand, TGA results revealed increase in the thermal stability. Also the results showed the effect of the EVO weight and the epoxy content (O.O value) on the improvement of the properties of PLA. ESO6.5 % at 20wt% was an efficient plasticizer for PLA.

Automated summary

This study aimed to improve the low intrinsic ductility of poly (lactic acid) (PLA) by using a novel bio-sourced plasticizer, resulting in a fully biodegradable material suitable for film manufacturing. The addition of epoxidized sunflower oil (ESO) at 6.5% in a 20wt% PLA blend was found to be an effective plasticizer, increasing elongation and enhancing thermal stability. The plasticizers decreased tensile strength and modulus of PLA, while increasing elongation at break.