Session: PMSE/POLY Poster Session:

Imparting porosity to 3D printed polymeric materials is an attractive option for producing lightweight, flexible, customizable objects such as flexible sensors and shoe midsoles. Although methods currently exist to introduce pores into 3D printed objects, little work has explored the structure-property relationships of these materials. In this study, we produced and printed paraffin/photopolymer composite inks by a direct ink writing (DIW) technique that leveraged paraffin particles as sacrificial viscosity modifiers in a matrix of photocurable resin. After printing, paraffin was dissolved by immersion in an organic solvent at elevated temperature, leaving behind the porous resin matrix. Rheometry experiments demonstrated that composites with between 40 and 60 wt% paraffin particles were able to be successfully 3D printed; thus, the porosity of printed objects can be tailored from 43 to 63 vol%. Scanning electron microscopy images demonstrated that closed-cell porous structures formed at low porosity values, whereas open-cell structures formed as porosity increased. Tensile tests revealed a decrease in elastic modulus as the porosity of the material was increased. These tests were also simulated using finite element analysis (FEA), and a model was found which accurately replicated experiments. Working in tandem, rheometry allows ink printability to be predicted, while FEA enables the design of complex structures with desired mechanical performance. Our printing method complements these predictions with tailorable porosity to facilitate the production of custom materials and geometries.

(A) As the porosity of the photopolymer resin matrix increases, the structure transitions from a closed-cell (left) to open-cell (right) structure. (B) Experimental tensile test results indicate that increased porosity decreases the elastic modulus, which is predicted by finite element analysis simulations.

(A) As the porosity of the photopolymer resin matrix increases, the structure transitions from a closed-cell (left) to open-cell (right) structure. (B) Experimental tensile test results indicate that increased porosity decreases the elastic modulus, which is predicted by finite element analysis simulations.

Taekwang Ha

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