(Thermo)mechanical and chemical characteristics of photochemically crosslinked acrylates from bio- and fossil-based origin

The acrylates with oligomers and monomers from (partially) bio-based feedstock become available at (semi-)industrial scale, which can be processed through photochemical crosslinking for applications in coatings, additive manufacturing, electronics, or inks. Although fossil- and bio-based acrylates may have a similar chemical composition, it requires good understanding of processing and structure-property relationships as minor changes in microstructure may strongly alter the performance. A comparative study on mechanical properties and chemical structure of bio- and fossil-based acrylates with different functionalities and backbone structures reveals higher ductility of bio-based acrylates, in relation with a more complex organization of the intrinsic molecular structure. The latter is confirmed by mechanical testing and visco-elastic characteristics (dynamic mechanical analysis) yielding lower stiffness and higher dampening of bio-based acrylates, in parallel with a lower glass transition temperature (differential scanning calorimetry). The complex molecular arrangements include a nanoscale morphology with ordered structure (X-ray diffraction), conformational changes (infrared spectroscopy), and a residual high-molecular weight fraction (size exclusion chromatography). The visco-elastic calculations indicate only 4% to 5% lower crosslinking density and around 10% higher mean molar mass of the polymer chains segments between chemical crosslinks and trapped chain entanglements, which explain the unique structure and performance of bio-based acrylates. image