Advantages and drawbacks of Thiol-ene based resins for 3D-printing

Abstract

The technology of 3D printing is conquering the world and awakens the interest of many users in the most varying of applications. New formulation approaches for photo-sensitive thiol-ene resins in combination with various printing technologies, like stereolithography (SLA), projection based printing/digital light processing (DLP) or two-photon polymerization (TPP) are presented. Thiol-ene polymerizations are known for its fast and quantitative reaction and to form highly homogeneous polymer networks. As the resins are locally and temporally photo-curable the polymerization type is very promising for 3D-printing. By using suitable wavelengths, photoinitiator-free fabrication is feasible for single- and two photon induced polymerization. In this paper divinyl ethers of polyethylene glycols in combination with star-shaped tetrathiols were used to design a simple test-system for photo-curable thiol-ene resins. In order to control and improve curing depth and lateral resolution in 3D-polymerization processes, either additives in chemical formulation or process parameters can be changed. The achieved curing depth and resolution limits depend on the applied fabrication method. While two-/multiphoton induced lithography offers the possibility of micron- to sub-micron resolution it lacks in built-up speed. Hence single- photon polymerization is a fast alternative with optimization potential in sub-10-micron resolution. Absorber- and initiator free compositions were developed in order to avoid aging, yellowing and toxicity of resulting products. They can be cured with UV-laser radiation below 300 nm. The development at Fraunhofer ILT is focusing on new applications in the field of medical products and implants, technical products with respect to mechanical properties or optical properties of 3D-printed objects. Recent process results with model system (polyethylene glycol divinylether/Pentaerithrytol tetrakis (3-mercaptopropionat), Raman measurements of polymer conversion and surface modifications using bifunctional crosslinkers are presented with advantages, drawbacks and a general outlook

Polymers for 3D Printing and Customized Additive Manufacturing

“…Using an SLA instrument with a 266 nm laser, thiol-vinyl ether resins without photoinitiator were selectively structured with feature sizes below 50 μm. 149 …”

Antimicrobial Thiol–ene–acrylate Photosensitive Resins for DLP 3D Printing

“…Moreover, fast polymerization rate of thiol–ene systems can increase the printing speed and decrease amount of photoinitiator , which reduces the cost and prevents the resin from yellowing. Thiol–ene binary systems have been applied to DLP 3D printing to fabricate objects with high resolution . Recently, our group reported a series of 3D printable thiol–ene systems with high stability.…”

3D Printing Amorphous Polysiloxane Terpolymers via Vat Photopolymerization

“…[30,[33][34][35][36] In this application, thiol-ene addition also provides highly advantageous spatiotemporal control through formation of crosslinked networks only at the times and locations of direct UV exposure. [34,37] For example, a recent report from Sirrine et al described simultaneous chain extension and crosslinking via thiol-ene coupling and acrylamide free radical homopolymerization, which enabled a relatively low viscosity photopolymer to provide properties of higher molecular weight precursors upon photocuring. [34] In another report, Wallin et al demonstrated VP of poly(mercaptopropylmethylsiloxane-codimethylsiloxane) and α,ω-divinyl PDMS, resulting in products with strains at break over 400% and actuatable printed objects.…”