Low‐Viscosity Limonene Dimethacrylate as a Bio‐Based Alternative to Bisphenol A‐Based Acrylic Monomers for Photocurable Thermosets and 3D Printing

Abstract

Bisphenol A glycidyl methacrylate (BisGMA) is well established as photocurable resin in dental restoratives and 3D printing. At present there are raising concerns regarding the estrogen‐mimicking bisphenol A (BPA) contamination of health care and consumer products. It is an important challenge to substitute BPA‐based resins for bio‐based cycloaliphatic monomers while lowering resin viscosity without sacrificing high stiffness and glass temperature. Particularly high viscosity is critical for 3D printing by photopolymerization. Unlike BPA the cyclic monoterpene limonene, extracted from citrus fruit peels, is safe in human uses. Herein it is reported on limonene‐based dimethacrylate (LDMA) tailored for 3D printing application and derived from limonene oxide (LO) and methacrylic acid (MA). Residual MA is converted into glycerol dimethacrylate (GDMA) serving as an in situ reactive diluent. The influences of temperature, catalysts, MA/LO stoichiometry, and the addition of glycidyl methacrylate (GMA) and magnesium oxide on the LDMA‐based resin performance are elucidated. As compared to BisGMA (560 Pa s) LDMA‐based resins exhibit significantly lower viscosity (5–117 Pa s) governed by the MA/LDMA molar ratio and the GMA addition. At 30 wt% LDMA content photocured resin yields thermosets having high Young’s Modulus (3.4–3.7 GPa), tensile strength (88–98 MPa), and glass transition temperature (119–135 °C), surpassing the performance of the corresponding BisGMA‐based resins.

UV-Curable Bio-Based Polymers Derived from Industrial Pulp and Paper Processes

“…Shimpf et al [ 108 ] tailored limonene-based dimethacrylate for 3D applications. They synthesized limonene dimethacrylate (LDMA) resins, starting from limonene oxide.…”

“… Examples of 3D printed objects: ( a ) double helix; ( b ) orange model; ( c ) model of Eiffel Tower; base resin was used as control (object on the left in pictures ( b , c ), printed formulation containing LDMA on the right of the cited imagines [ 108 ]. (Open access source: doi:10.1002/mame.202000210).…”

Manufacturing and photocrosslinking of a new bio‐based dimethacrylate resulting in hydrophobic crosslinked films

“…According to recent demands on more environmentally friendly and energy economic processes, the development of bio-based monomers and more energy-efficient light emitting diodes (LEDs) as radiation sources has received increased interest nowadays [7][8][9][10][11][12][13][14][15][16][17][18].…”

“…Therefore, renewable materials have attracted attention to replace materials originating from fossil sources. Furan dicarboxylic acid, limonene, nicotinic acid, resorcinol, oleic acid, d-fructose, and isosorbide depict examples for bio-based starting materials for methacrylate manufacturing [7][8][9][10][11][12][13][14][15][16]. Introduction of a methacrylate group into bio-based starting materials enables the application of wellknown polymerization mechanisms on the one hand and consequently stepwise substitution of fossil resources by renewable starting materials on the other hand.…”

“…Dimethacrylates are established monomers in photopolymerizing mixtures that have been used for the manufacturing of protecting coatings, printing plates, printing inks, three‐dimensional printing systems, tissue‐engineering matrixes, and dental composites [1–6]. According to recent demands on more environmentally friendly and energy economic processes, the development of bio‐based monomers and more energy‐efficient light emitting diodes (LEDs) as radiation sources has received increased interest nowadays [7–18]. Therefore, renewable materials have attracted attention to replace materials originating from fossil sources.…”