Additive Manufacturing of Hydrocarbon-Based Elastomers and Composites

Additive manufacturing (AM) gathers increasing attention for its customization and sustainability benefits, including material efficiency, lightweighting, and energy conservation. This dissertation explores innovative strategies for 3D printing elastomers using vat photopolymerization (VP) and direct ink writing (DIW). The first study introduces a strategy for incorporating high molecular weight isoprene rubber latexes into VP to address the challenges of processing elastomers. The addition of water-soluble monomers and crosslinkers to the latex aqueous phase yielded a photocurable, low-viscosity precursor suitable for VP. Photopolymerization in the aqueous phase created a hydrogel scaffold surrounding the polymeric particles, solidifying the latex into a green body. Post-processing removed water, driving the coalescence of isoprene rubber particles and resulting in a semi-interpenetrating polymepost-processing) with exceptional elongation at break up to 600%. Expanding on this, VP of sulfonated ethylene-propylene-diene monomer (sEPDM) latex demonstrated the 3D printing of olefinic elastomers. The sEPDM formed a physically crosslinked network due to ionic aggregation, leading to an interpenetrating polymer network (IPN) with tunable mechanical properties after sEPDM particles coalesced throughout the scaffold network during the post processing of printed green body. The introduction of polymerizable counterions for sulfonate groups at the sEPDM particle interfaces created a novel photocuring mechanism for latexes. The copolymerization of monomer added in the aqueous phase and 2-(Dimethylamino)ethyl methacrylate (DMAEMA) at the sEPDM particles generated a physically crosslinked hydrogel network through the ionic association on the latex particle interfaces. The absence of covalent crosslinked network highlighted the potential of 3D printing reprocessable materials. The last two projects utilized hybrid colloids composed of inorganic nanoparticles and styrene-butadiene rubber (SBR) particles for the 3D printing of polymer composites. The mixture of silica nanoparticle colloid and SBR latex demonstrated shear yield-stress behavior, enabling DIW. The modification of silica nanoparticle surface functionalities tuned the interaction between the silica and the polymer matrix, influencing the material mechanical properties. Electrically conductive fillers, single-wall carbon nanotubes (SWCNTs), were applied in SBR hybrid colloids to demonstrate VP of SWCNT-SBR composites. The results revealed enhanced electrical conductivity of the composites with increased SWCNT content, demonstrating the potential application of 3D printing elastomeric conductive materials.