Abstract
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 (Tg) and melting temperature (Tm) 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.
Highlights
Research in biodegradable polymers has received increased attention in recent years because of their wide application in environmental friendly packaging
The results showed that the addition of epoxidized sunflower oil (ESO) or epoxidized soya bean oil (ESBO) to polylactic acid (PLA) decreased tensile strength and tensile modulus compared to neat PLA but increased elongation at break for which an optimum (9.02%, 15.55% and 33.67% for ESBO, ESO5.5% and ESO6.5% respectively) was reached at a content of 20 wt% of plasticizer
DSC showed a clear decrease in the glass transition temperature of PLA and scanning electron microscopy (SEM) analysis proved successful modification on the PLA brittle morphology with addition of epoxidized vegetable oils (EVO)
Summary
Research in biodegradable polymers has received increased attention in recent years because of their wide application in environmental friendly packaging. PLA is a polyester that can be produced from lactic acid derived from renewable resources. It is one of the most frequently used biodegradable polymers, especially in packaging applications because of its high strength, high modulus, good transparency, processability, and biocompatibility. Considerable efforts have been carried out to improve the properties of PLA so as to compete with low cost and flexible commodity polymers. These attempts include blending PLA with other polymers [1], modifying PLA with plasticizers [2, 3], or blending with mineral fillers composites [4]
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