Physical and structural characterisation of starch/polyester blends with tartaric acid

• Tartaric acid (TA) was efficient as compatibiliser of starch/PBAT blends.
• Film properties were analysed based on the modelling of the mixture design.
• Greater proportions of TA resulted in more opaque and less soluble materials.
• Esterification reactions promoted by TA were characterised by FT-IR and 13C CPMAS NMR.
• Compatibilised blends with TA showed better morphological and mechanical properties.

Starch/PBAT blends were produced by reactive extrusion with tartaric acid (TA) as an additive. The effects of TA, glycerol and starch + PBAT on the mechanical, optical and structural properties of the films were evaluated, with formulations based in a constrained mixture design. Tartaric acid acts as a compatibiliser and promotes the acid hydrolysis of starch chains. These two functions explain the observed film resistance and opacity. TA reduced the weight loss in water. Scanning electron microscopy (SEM) images showed that TA reduces the interfacial tension between the polymeric phases, resulting in more homogeneous films. Nuclear magnetic resonance (13C CPMAS) and Fourier transform infrared spectroscopy (FT-IR) suggest that tartaric acid is able to react with the hydroxyl groups of the starch by esterification/transesterification reactions, confirming its role as a compatibiliser. The addition of TA results in materials with better properties that are suitable for use in food packaging.