Camphoric acid as renewable cyclic building block for bio-based UV-curing polyhexylene itaconate

Polymer resins, such as polyester-, polyurethane- and alkyd resins are frequently applied as binder component in paints, printing inks, coatings or materials for additive manufacturing. Besides aliphatic building blocks with different chain lengths, cyclic monomers are used as starting materials, to increase the hardness of the resulting coatings materials. For this, mostly aromatic compounds derived from petrochemical sources, such as phthalic anhydride, isophthalic acid or terephthalic acid are being used. Monomers from renewable resources with similar chemical structures and chemical properties are scarce. In this study, (1R,3S)-(+)-camphoric acid is used as alternative building block for UV-curing polyester resins derived from itaconic acid and 1,6-hexanediol. The properties of both resins and final materials are compared to similar resins derived from isophthalic acid. In both cases, the incorporation of the cyclic monomer led to an increase in glass transition temperature, as well as viscosity of the resins. Thermal as well as mechanical properties of the cured materials were also improved in comparison to a resin without any cyclic building block incorporated.