Fully Biobased Polyesters Based on an Isosorbide Monomer for Coil Coating Applications

In this work, novel fully biobased polyester resins are presented for use as binders in the field of coil coating technology. These new materials are based on the copolymerization of isosorbide (ISo) with different industrially available aliphatic biobased building blocks. In order to assess the effect of chemical composition on the chemical-physical properties of such biobased polyester resins, the amount of ISo was systematically varied (18-36 wt %), and the molecular weight and thermal response of the resulting materials were evaluated by means of gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. It was found that by tuning the ISo content in the resins, their glass transition temperature (T g ) could be controlled (-22 to 28 °C) without considerably affecting their molecular weight (in the range of 4000-5000 g/mol). The resulting cross-linked coatings (both clear and pigmented) were found to exhibit excellent mechanical properties as well as chemical and photochemical durability, as evidenced by comparative microindentation, hydrolysis, and accelerated weathering tests conducted on the new biobased systems and on commercial oil-based benchmarks. The results of this study demonstrate a versatile approach to tune the chemical-physical response of fully biobased polyester coatings and provide evidence of the potential of ISo-based polyester binders as sustainable high-performance materials for coil coating applications.