Unsaturated polyester (UPE) resins enjoy numerous uses as structural adhesives in glass fiber laminates, concrete flooring, and masonry repair. Typical UPE resins consist of a UPE oligomer with up to 50 wt% of a reactive diluent such as styrene, which ultimately provides the cured resin with its thermal and mechanical properties. The ability of these resins to cure rapidly under UV light in conjunction with a photoinitiator makes them amenable to vat photopolymerization (VP) 3D printing. However, the volatility and toxicity of styrene limits the use of traditional UPE resins for VP. This study utilizes a nonvolatile, styrenic-based ionic liquid as a crosslinker to produce UPE resins suitable for VP 3D printing. UPE oligomers containing 0, 25, and 40 mol% of phthalic anhydride (PA) in the backbone were synthesized to study the effect of saturation content on photocuring kinetics. Utilizing diglyme as a nonreactive, low-volatility diluent provided homogeneous solutions of the UPEs and ionic liquid crosslinker. Photorheological experiments revealed an increasing cure time with increased PA content in the backbone. Likewise, the cure time rose drastically with increasing diglyme content from 20 to 50 wt%. Photorheology also revealed that the cure time remained largely unchanged upon varying the crosslinker content from 0 to 40 wt% when all other variables were kept the same. Thermogravimetric analysis further showed an increase in the 5 wt% decomposition temperature of the cured resins from 215 to 280 °C as the ionic liquid content increased from 0 to 40 wt%. VP of a selected UPE resin afforded geometrically complex 3D printed structures demonstrating the ability of this method to utilize a common industrial feedstock as part of a novel VP resin. Finally, 3D printed test specimens exhibit ionic conductivities spanning from 10-8 to 10-5 S cm-1 between 60 and 150 °C indicating a potential additional functionality for 3D printed UPE parts.

3D printing of unsaturated polyester networks

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.