High temperature vat photopolymerization 3D printing of fully bio-based composites: Green vegetable oil epoxy matrix & bio-derived filler powder

Abstract

Additive manufacturing (AM) is a well-established process which allows to generate complex and accurate geometry required in several applications, from medical to automotive area. The exploitation of polymer resin into additive manufacturing needs to overcome the problem of viscosity and reactivity which can be improved by high temperature vat photopolymerization (VPP). Moreover, the concern about climate change and depletion of fossil fuels arises the requirement to move toward bio-derived products which can substitute the commercially available resins without compromise the final properties. In order to close this gap, we have studied vegetable epoxy oil polymer resins as main component for new bio-derived formulations which can be used in vat photopolymerization 3D printing. Furthermore, knowing the limits of the vegetable oils in terms of final properties, the investigation explores the possibility to 3D printing bio-derived composites by adding bio-based fillers, such as wall-nut shell. The UV-curing process was investigated by photo-DSC and photorheology to verify the feasibility of AM. Then, the effect of the presence of the filler on the UV-process was assessed and finally we successfully 3D printed composites of different geometries. The thermo-mechanical properties of the thermoset materials were studied by dynamic analysis and tensile testing. The benefit of the addition of the filler was confirmed and explained by investigating the surface modification of the filler which had an incredible impact on the properties of the composite. Finally, we pursuit the possibility to chemically degrade the thermoset joining the proof-of-concept of circular economy.