The University of Akron,
Keywords: Polymer composites, 3D printing, thermoplastic elastomer, graphene
Summary:Additive Manufacturing or 3D printing of polymers has progressed tremendously in the past decade with various technologies including photopolymerization, extrusion, and powder-based methods. Beyond one component 3D printing, additive manufacturing of polymer composites, however, still faces major challenges such as incompatible processing conditions, low printing quality, and poor internal structure control. To address those issues, we have been working on designing polymer composites with unique physical properties and high 3D printability for functional additive manufacturing. In the first part, I will discuss our recent progress in designing thermoplastic elastomers (TPEs) and their blends for additive manufacturing of soft, stretchable, and biocompatible structures. Polyisobutylene (PIB)-based TPEs including poly(styrene-b-isobutylene-b-styrene) (SIBS) copolymers and PIB-based polyurethanes have been successfully used for fused filament fabrication (FFF) 3D printing. The microphase-separated structure of TPEs can be precisely tuned by adjusting the hard to soft block ratio and blending with rigid homopolymers. Butyl rubber and its nanocomposites have been successfully 3D printed with solvent-assisted direct ink writing (DIW) by adjusting the rheological, mechanical, and electrical properties with nanoclay and graphene. Soft and stretchable strain sensors based on the 3D printed structures were also demonstrated. In the second part, I will discuss our recent work in designing polymer composite particles for selective laser sintering (SLS) 3D printing. SLS has several unique advantages including the ability to fabricate complex geometries without support structures, highly isotropic properties of the printed parts, batch production of multiple parts in one printing. However, currently there are very limited types of polymer powders available for SLS, with over 95% being polyamide. To address this limitation, we have developed a hybrid approach for the scalable synthesis of polyolefin composite particles, which exhibit narrow size distribution, regular shape, and excellent SLS 3D printability. The processing-structure-property relationship of the polymer composite powders and 3D printed parts was also systematically elucidated. Key references: Xu et al. ACS Appl. Polym. Mater. 2021, 3, 4554; Macromol. Rapid Commun. 2022, 2200109; MRS Commun. 2022, 12, 597–602; Polymer 2020, 210, 123033.