Prediction of ceramic stereolithography resin sensitivity from theory and measurement of diffusive photon transport

Abstract

A general, quantitative relationship between the photon-transport mean free path ͑l * ͒ and resin sensitivity ͑D P ͒ in multiple-scattering alumina/monomer suspensions formulated for ceramic stereolithography is presented and experimentally demonstrated. A Mie-theory-based computational method with structure factor contributions to determine l * was developed. Planar-source diffuse transmittance experiments were performed on monodisperse and bimodal polystyrene/water and alumina/monomer systems to validate this computational tool. The experimental data support the application of this l * calculation method to concentrated suspensions composed of nonaggregating particles of moderately aspherical shape and log-normal size distribution. The values of D P are shown to be approximately five times that of l * in the tested ceramic stereolithography suspensions.

Predictive models for the photopolymerization of ceramic suspensions

“…7,8 There is no closed-form expression for S(Φ), as it is the product of a form factor containing the scattering power for single particles and a structure factor accounting for particle-particle interactions. 7 Since there is no closed-form theoretical expression for S, it can be approximated with an empirical function that has the behavior that S increases linearly with concentration at low Φ, but then reaches a maximum at Φ max .…”

“…Several approaches have been taken, relating the depth of cure to the energy dose by modified Beer-Lambert 5 via Kubelka-Munk modeling 6 and by explicitly considering light scattering. 7,8 In this paper, we present a simple predictive model that considers several attenuation processes, including absorption by the photoinitiator, by an inert UV absorber, and attenuation by light scattering from suspended particles.…”

Optical characterization of stereolithography alumina suspensions using the Kubelka–Munk model

“…5,13,14 Griffith and Halloran 5 related this parameter to the square of the refractive index difference between the ceramic particles and the medium ( n 2 = (n p − n 0 ) 2 ), to the interparticle spacing 0955-2219/$ -see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2008.07.008 (s) and to the UV wavelength (λ) via the expression:…”

“…More recently, Wu et al 13 related the depth of penetration to the photon transport mean free path (l*):…”

“…2 Several formulations containing at least 40 vol.% of ceramic powder have been developed to ensure (i) an adequate rheological behavior for spreading homogenous thin layers, (ii) to be reactive to UV and, (iii) to lead dense parts after heat treatment. [3][4][5][6][7][8][9][10][11][12][13] However, the introduction of ceramic particles in monomer reactive systems increases a level of complexity due to multiple scattering phenomena witch reduces the cure depth and thereafter increases the processing time and dimensional resolution.…”