3D printed porous silicone polymer composites using table salt as a sacrificial template†

Abstract

Porous silicone polymer composites (elastomeric foams) with tunable properties and multifunctionalities are of great interest for several applications. However, the difficulties in balancing functionality and printability of silicone polymer based composite resins hinder the development of 3D printed multifunctional porous silicone materials. Here, the direct ink write (DIW) technique and NaCl filler as a sacrificial template were utilized to develop 3D printed porous silicone composites. Three different fillers (hydrophilic and hydrophobic fumed silica, and carbon nanofibers (CNF)) were used to impart additional functionality and to explore their effects on the rheology of the DIW resin, and the mechanical properties of the 3D printed elastomeric foams. While hydrophilic silica was effective in modulating the rheology of the resin, CNFs were effective in improving the tensile strength of the elastomeric foam. Unlike tensile strength, which was found to be dependent on filler type, the uniaxial compressive behavior was found to be more dependent on the porosity of the elastomeric foams. A hyperelastic constitutive model (the Compressive, Hyperelastic, Isotropic, Porosity-based Foam model) was used to simulate the uniaxial compressive behavior of the elastomeric foams, and the model accurately reproduced the experimental stress–strain profiles. The expanded design flexibility of tunable porosity in DIW parts enables the foams to be utilized in a wider variety of applications. For example, the foam with CNF filler demonstrated excellent oil/water separation capacity, with absorbing efficiencies of 450% and 330% respectively for chloroform and toluene. Similarly, a foam with hydrogen getter capacity was developed using the CNF filled foam with hydrogen getter as an additional functional filler, and high performance of the 3D printed hydrogen getter composite was demonstrated.