A systematic study of vat-polymerization binders with potential use in the ceramic suspension 3D printing

The primary focus of this study is to offer guidelines for developing binder formulations for visible light photoinduced ceramic 3D printing applications. Different monomer combinations with a variety of functional groups were mixed at various ratios to systematically study their rheological and curing behaviour, and mechanical properties (ultimate tensile strength, elongation at break, Young’s modulus). The optimum ratios of monomer blends were investigated by adjusting the balance of difunctional monomers (HDDA and Photocentric 27) and multifunctional monomers (tri- and tetrafunctional - PPTTA, Photocentric 34 and PE(EO)nTTA) at the weight rates of 20:80, 40:60, 50:50, 60:40, 70:30 and 80:20. The key curing parameters (penetration depth D_p and critical exposure energy E_c) were calculated by fitting values based on curing thickness (C_d), using Jacobs' Basic Working Curve Equation, to estimate optimum printing exposure time for each mixture. Although the curing performance of the mixtures was enhanced by increasing the functionality and molecular weight of the monomers in the mixture, the best viscosity and mechanical properties were obtained when difunctional monomers were mixed with a trifunctional (meth)acrylates. Two types of difunctional monomers were used in the mixtures and showed a similar performance. The best ratio between di- and trifunctional monomers were 50:50 and 40:60 wt ratios, yielding the best mechanical properties and minimum viscosity required for ceramic slurry mixtures. Moreover, the effect of vinyl-based monofunctional monomers as reactive diluents as well as hexa-functional monomers as cross-linkers on the shortlisted formulations was studied. This work summarises the best binder base choices for the daylight curable ceramic suspensions, used in LCD screen printing applications, and further works mcust be done to find the best debinding cycles.