New more sustainable resins for 3D printing

In recent decades, additive manufacturing or 3D printing has gained a lot of importance as new technologies such as computer design are being developed, since it allows the manufacture of high-resolution three-dimensional objects on demand quickly and easily.

“Among other 3D printing techniques -explains Oihane Varela Manrique- tank printing, in which a liquid resin sensitive to ultraviolet light is selectively cured (solidified) by means of ultraviolet light, is the process by which higher resolution three-dimensional objects and better mechanical properties.

However, the variety of resins available for 3D printing using this technique is limited, and the vast majority of commercial resins are based on (meth)acrylate groups, so the degradability and recyclability of these materials is low.” Consequently, and with the aim of developing potentially recyclable and therefore more sustainable printable resins, Oihane Varela, recently graduated from the Faculty of Chemistry of the University of the Basque Country (UPV/EHU), has based her Final Degree Project on the study of the use of special polythiourethane resins for tank printing.

“There are different types of 3D printing -explains Oihane Varela. The best known or used due to its simplicity and low price is extrusion printing, in which a solid polymer is melted and extruded while it is deposited in an orderly manner to form the desired object. But, thanks to tank 3D printing, complex parts with better resolution and quality can be obtained at a reasonable speed. In this case, Varela and his colleagues use a liquid resin and, by irradiating light with a specific shape, the resin solidifies in the desired shape, thus manufacturing the piece layer by layer. With the new technique, it is feasible to obtain materials with different properties, depending on the starting products that we use; which demonstrates the versatility of the system and gives rise to a wide variety of potential applications. In this sense, 3D printing offers the opportunity to create complex parts on demand; so it has many applications in fields such as biomedicine, jewelry, in the automotive sector…“

Oihane Varela in a laboratory at the Faculty of Chemistry. (Photo: UPV/EHU)

The process that is carried out is simple. “Several latent basic catalysts, also known as Photobase Generators, have been synthesized and characterized for use in 3D printing. It has been shown that the analyzed system shows good stability in the dark and rapid polymerization when irradiated with ultraviolet light. Through photorheological and thermal studies, the viscoelastic behavior of different resins has been investigated and the best formulation for its implementation in 3D tank printing has been determined. Subsequently, these formulations have been studied in a 3D tank printer in which the most important parameters have been determined and optimized, achieving the printing of good resolution parts. “

Therefore, in this work it is concluded that resins based on polythiourethane and catalyzed by means of Photobase Generators appear as a new alternative to conventional resins, since materials with diverse properties can be obtained in a simple way. On the other hand, because the materials obtained show good recyclability, they appear as potential candidates in the development of more sustainable 3D printing materials. (Source: UPV/EHU)