Photopolymer is a kind of polymers that undergoes changes of its physical properties typically from liquid monomers/oligomers to solid thermosets when exposed to a light source. Photopolymer material is a critical component for advanced manufacturing technologies particularly for 3D printing using stereolithography (SLA), digital light processing (DLP), and multi-jet printing (MJP). The SLA is an additive manufacturing method using UV-curable resin and computer-aided design (CAD) software. The CAD reconstructs the desired 3D object images into many 2D slices, which are printed typically layer-by-layer by the photopolymerization of liquid resins in a vat using UV or deep-blue laser.
Viscosity of photocurable resin is one of key physical parameters to determine which 3D printing technology could be applied. Vat photopolymerization technologies, such as SLA and DLP, needs viscous monomer/oligomer liquid resins to control the photopolymerization within the UV-illuminated regions. In contrast, material-jetting photopolymerization, such as MJP from 3D Systems and PolyJet from Stratasys, requires low viscosity liquid resins that can be jet-printed and then cured under a UV lamp for the layer-by-layer printing. The low viscosity of the ink-jet photocurable resins enables (i) more reactive and faster curing than photopolymers used for SLA and DLP and (ii) the multicolor 3D object printing.
In this presentation, in addition to the introduction of 3D printing technologies based on photopolymerization, we will discuss the tailoring of UV-curing kinetics of high-viscosity epoxy monomers using reactive diluents for photoinitiated cationic polymerization. Oxetane and epoxy-based reactive diluents are compared not only to reduce the viscosity of the liquid resins, but also to increase their photopolymerization reactivity under continuous UV irradiation. We will highlight the use of oxetane-based reactive diluents to improve the rate of polymerization, while exhibiting higher reactivity at relatively lower dilutions compared to epoxy-based reactive diluents.