Vat photopolymerization of olefinic elastomers from sulfonated ethylene-propylene-diene monomer (EPDM) latexes

Ethylene-Propylene-Diene Monomer (EPDM) rubber is recognized for elasticity over a wide temperature range and exceptional resistance to UV light and oxidative degradation. In this study, sulfonated EPDM (sEPDM) latex serves as an innovative platform for 3D printing olefinic elastomers through vat photopolymerization (VPP). The sulfonation of EPDM and subsequent neutralization with potassium hydroxide enabled the production of waterdispersible sEPDM (K-sEPDM), yielding a stable latex with an average particle diameter of 125 nm. The inherent low viscosity of the latexes allowed the direct application of elastomeric polymers during the VPP process. The photopolymerization of a scaffold precursor composition, which consisted of n-vinylpyrrolidone (NVP) and poly (ethylene glycol) diacrylate (PEGDA) in the aqueous phase of K-sEPDM latex, solidified the latex as a particle embedded hydrogel. Post-processing for removing water from the 3D printed green body facilitated coalescence of the K-sEPDM particles throughout the scaffold network, generating a second ionically crosslinked network together with scaffold as an interpenetrating polymer network (IPN). Tensile testing demonstrated tunable elastomeric properties with an ultimate strain from 315+11-453+37 % and ultimate stress from 7.6+0.5-8.2 +0.3 MPa with excellent thermal recoverability. VPP of photocurable K-sEPDM with a commercial printer showcased high-resolution printing capabilities with controllable isotropic shrinkage for the printing of olefinic elastomers.