The influence of multifunctional dendritic oligomers on material properties for vat polymerization

Stereolithography is a state-of-the-art 3D-printing technology that has increasing impact in the dental, hearing-aid and bioprinting industries. The mechanical quality of the final product is highly dependent on the composition of the resin, polymerization kinetics and conversion rate achieved during the printing process (Watts in Dent Mater 21:27-35, 2005; Uzcategui et al. in Adv Eng Mater 20:1800876, 2018). The object of this research was to assess the influence on mechanical characteristics of different molecular weight oligomers and multifunctional dendritic oligomers as crosslinkers in resins. It analyzed the resins conversion rate using FTIR spectroscopy and its impact on the viscosity using rotational (UV)-rheometry. The investigation on the influence of different molecular weights of the aliphatic oligomers were conducted on pure substances with TPO as initiator, while the study of multifunctional crosslinkers used a base material formulation containing two bifunctional polyurethane (meth)acrylate oligomers and TPO as foundation. It incorporated bi-, tri-, tetra- hexa-, and octadeca-functional acrylate crosslinkers which were maintained at an equal ratio of crosslinking to oligomer functional groups. The study demonstrated that mechanical properties can be effectively modulated through the incorporation of long-chain oligomers, revealing an inverse relationship between the Young’s modulus and strain. In addition, investigations into crosslinkers indicated that it can also be utilized to influence the mechanical properties without the inverse behavior of young’s modulus and strain. Large oligomers and crosslinkers significantly increased the viscosity of the resins at room temperature and, therefore, influenced the manufacturing process (Cross in J Appl Polymer Sci 13:765-774, 1969). Incorporating multifunctional dendritic oligomers as crosslinkers allows precise tuning of resin behavior and mechanical properties.