Paper Number
VP32 

Session
Pre-recorded Flash Presentations (virtual)

Title
Photopolymerization of methacrylate: From conversion via rheology to mechanical properties

Presentation Date and Time
All Week (Asynchronous) Any Time

Track / Room
Pre-recorded Presentation / Virtual

Authors (Click on name to view author profile)

  1. Anastasio, Rosaria (Eindhoven University of Technology, Department of Mechanical Engineering)
  2. Peerbooms, Wouter (Eindhoven University of Technology, Department of Mechanical Engineering)
  3. Steensma, Nienke (Eindhoven University of Technology, Department of Mechanical Engineering)
  4. Cardinaels, Ruth (KU Leuven, Chemical Engineering)
    Cardinaels, Ruth (Eindhoven University of Technology)
  5. van Breemen, Lambèrt (Eindhoven University of Technology, Department of Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Rosaria Anastasio1, Wouter Peerbooms1, Nienke Steensma1, Ruth Cardinaels2,1 and Lambèrt van Breemen1
1Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands; 2Chemical Engineering, KU Leuven, Leuven, Belgium

Speaker / Presenter 
Cardinaels, Ruth

Keywords
additive manufacturing; applied rheology

Text of Abstract
Stereolithography is an additive manufacturing process in which products are built layer-by-layer from a photo-curable liquid. Typically, the mechanical properties of the 3D-printed product are affected by material heterogeneity along the sample thickness. To study the effect of process conditions on the material properties without sample heterogeneity, single layers of a UV-curable polymer are characterized [1]. Whereas our earlier work showed that the resin formulation significantly affects the network formation [2], our present work focusses on the effects of processing conditions. First, the evolution of monomer conversion with irradiation time is studied by means of FTIR spectroscopy. A model is developed based on the reaction kinetics of photopolymerization that describes the experimental data and predicts the effects of initiator concentration and light intensity on monomer conversion with reasonable accuracy [3]. This model is then used to analyze the effects of pulsed irradiation on the curing kinetics, a phenomenon which is highly relevant when 3D printing multiple layers. The network development during photopolymerization, under various conditions of light intensity, pulse duration and dark time is monitored via oscillatory rheology with in-situ UV illumination. Pulsed irradiation clearly affects the curing kinetics while the final network modulus is rather insensitive to the dark time. Finally, the relations between UV illumination and ultimate network characteristics such as glass transition temperature Tg and yield stress are investigated. Although Tg is uniquely related to conversion, independent of light intensity and curing time, such a relation is not present for the yield stress. Moreover, the yield stress is not uniquely related to the distance to Tg. This indicates that the generated polymeric network microstructure depends on the processing conditions. [1] Anastasio et al. Polymer 2018 [2] Anastasio et al. J. Appl. Polym. Sci. 2020 [3] Anastasio et al. Macromolecules 2019