Limonene-derived polycarbonates as biobased UV-curable (powder) coating resins

The evaluation of poly(limonene carbonate)s (PLCs), derived from orange oils and carbon dioxide, as UV-curable (powder) coating binders is described. PLCs with moderate molecular weight were prepared by copolymerization of limonene oxide with CO2 and a subsequent molecular weight reduction step by transcarbonation with 1,10-decanediol (1,10-DCD). These PLCs were cured with a trifunctional thiol monomer in the presence of a photoinitiator via thiol-ene chemistry to form poly(thioether-co-carbonate) networks. The UV curing of the resins following solvent casting was studied at 130 degrees C using ATR-FTIR, revealing a fast curing and a quick thiol-ene network (TEN) formation, realized by the addition reactions of thiol groups of the curing agent onto pendant isopropenyl groups of PLC. An ene addition enhanced by thiol-ene crosslinking was also observed, known as a 'cage effect', which was discovered for the first time in a UV-curable thiol-ene system. The efficient TEN formation was also evidenced by the high sol fractions in those UV-cured samples and their dynamic mechanical thermal analysis (DMTA). The DMTA results of these TENs showed high Tgs (up to 125.9 degrees C) and a wide range of thermomechanical properties, including rubbery moduli from 4.4-27.5 MPa. The UV-cured powder coating employing PLCs as binders showed outstanding properties such as high transparency, good acetone resistance, high pencil hardness (H-2 H) and high Konig hardness (174-199 s), suggesting their potential as very promising biobased alternatives to conventional powder coating resins.

Automated summary

The evaluation of poly(limonene carbonate)s derived from orange oils and carbon dioxide as UV-curable coating binders showed fast curing and quick thiol-ene network formation. The UV-cured powder coating employing these PLCs exhibited outstanding properties such as high transparency, good acetone resistance, high pencil hardness and high Konig hardness, indicating their potential as promising biobased alternatives to conventional powder coating resins.