Synthesis of esters derived from 2,5-furandicarboxylic acid and study of its plasticizing effects on poly(lactic acid)

This study addresses the synthesis of three esters from 2,5-furandicarboxylic acid with different alcohols to a one-pot reaction through acid catalysis to evaluate them as biobased plasticizers for poly(lactic acid) (PLA). The 1H-NMR and FTIR analysis revealed the chemical structure of the synthesized plasticizers: dibutyl furan-2,5-dicarboxylate (DBF), di(2-methylbutyl) furan-2,5-dicarboxylate (DMBF) and didodecyl furan-2,5-dicarboxylate (DDF). The films of PLA and plasticized PLA, with contents up to 20 wt.% of plasticizer, were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and mechanical analysis. The results highlight that the plasticizer’s chemical structure and molecular weight affect the thermal and mechanical properties of the blends. In detail, DBF and DMBF were more effective in reducing the glass transition temperature (Tg), cold crystallization temperature (Tcc), and melting temperature (Tm) due to the ease of these low weight plasticizers to blend with PLA leading to the increase in chain mobility, which consequently increased the degree of crystallization. DDF was only effective in low concentrations (2.5 and 5 wt %); as concentration increases, the more pronounced phase separation becomes. The DMA results showed that all the plasticizers investigated decreased the Tg of PLA, with greater reduction for plasticizers having the lowest molecular weight. The elongation at break and tensile strength increased by incorporating 15 and 20 wt.% of DMBF, indicating a good compromise between flexibility and strength. Thus, DMBF showed more attractive potential as a "green" plasticizer for PLA, followed by DBF to produce packaging films.