We report compositions and methodology for creating 3D printed hydrogen-blown polysiloxane foams with controllable properties using direct-ink-write with active mixing. Though hydrogen-blown polysiloxane foam formulations are known to the community, these materials have not yet before been applied to 3D printing. Addition of hydrogen-blowing agents to polysiloxane resins produces hydrogen gas bubbles, resulting in a closed-cell pore structure. Incorporation of thixotropic agents to induce shear-thinning behavior imparts direct-ink-writability to the resin. The foamed resin can be printed and cured to produce a porous solid with two topologies of porosity: closed-cell intrastrand and open-cell interstrand. The intrastrand porosity can be controlled by variation in the mixing speed and the interstrand topology can be controlled by the print geometry, resulting in a facile method to vary the porosity of a single resin formulation or to produce variable porosity within a single printed part. Inter- and intrastrand porosities produce different load deflection behavior, so adjusting the ratio of closed- to open-cell porosity affords the ability to fine-tune the stiffness at different stresses by changing only the printing parameters.

Three-dimensional printed hydrogen-blown polysiloxane foams

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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