(242a) Additive Manufacturing and Multimaterial Printing with Fully Compounded Elastomers

Additive manufacturing offers potential for many new applications, particularly for custom products and low volume manufacturing. One challenge is the need for new and optimized materials. While there exist numerous examples of elastomer printing, the ability to print fully compounded thermoset elastomers (rubber, carbon black, cure package) remains a challenge due to their high viscosity and the need to avoid cure while printing. Fully compounded elastomers offer advantages, such as elastic recovery, high elongation, heat and solvent resistance, combined with design flexibility. Another constraint for 3D printing of highly flexible materials using conventional FDM systems is buckling of the filaments. In this work, a novel ram-type system (Additive Ram Material Extruder (ARME)) that can overcome these issues is described. The effect of elastomer properties, cure system, carbon black loading on the printability has been investigated for both nitrile rubber (NBR) and ethylene propylene diene monomer (EPDM) with different cure packages (sulfur and peroxide) and carbon black loadings. Initial results found that printed roads showed as high as 65% post-print shrinkage, which was reduced to less than 6% by modification of the rubber formulations. A two head system was developed to enable thermoset-thermoprinting dual printing capability. Combining thermosets and thermoplastics in injection molding can be challenging, but 3D printing allows for a wider range of material sets to be printed with strong adhesion. Different materials were printed, and the adhesion was evaluated for different elastomer and thermoplastic material sets, as well as the influence of key process parameters on adhesion. Results showed that curing conditions impact the interfacial strength between the materials.