Effect of molecular weight and concentration of dispersants on the slip, 3D printing and sintered bodies of hydroxyapatite.
DAVISON A. 1, KELLEHER M. 1, DEBARRA E. 2, RAFFERTY A. 3, HAMPSHIRE S. 2
1 School of Mechanical Engineering, Faculty of Engineering & Built Environment, Technological University Dublin, Bolton St, Dublin 1, Ireland, Dublin, Ireland; 2 The Bernal Institute, University of Limerick, Limerick, Ireland, Limerick, Ireland; 3 Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) & Advanced Materials and Bioengineering Research (AMBER) Centre, Trinity College Dublin, Dublin 2, Ireland, Dublin, Ireland
Dynamic light projection (DLP) printing is an additive manufacturing technique that uses photocurable liquid resins. The suspension is required to have a viscosity below 3000 mPa.s at a shear rate of 10 s-1. Achieving slips with low viscosities and sedimentation rates, and a high percent of ceramic powder is challenging. Dispersants are used to separate ceramic particles from each other and reduce the viscosity of ceramic slips. This study investigates the effect of four dispersants with different molecular weights on the characteristics of the slip, DLP printing, green and sintered bodies containing hydroxyapatite powder (D50 of 6.52 microns).
The characteristics of the as received hydroxyapatite powder were determined using SEM, XRD, TGA, BET surface area and particle size analysis. The specific surface area, phase and mass loss are 5.470 m2 g-1, 100% hydroxyapatite and 3% up to 600oC, respectively. The mean molecular weight of the primary peak for the four dispersants, D2155TF, D2001, D2155, D111, determined using gel permeation chromatography, are 1050, 1152, 6074 and 9289 g mol.-1 respectively. FTIR analysis was used to determine the primary polymers present.
The viscosity and stability of the slips containing different concentrations of the four dispersants with several concentrations of ceramic powder were determined. A DLP printer was used to determine their effect on the cure depth. The characteristics of the green and sintered bodies were then analysed. A strong relationship was found between the type (molecular weight) and concentration of dispersants and the characteristics of the slip, printed, green and sintered bodies containing hydroxyapatite powder.