Paper Number
AM3 

Session
Additive Manufacturing and Composites

Title
3D printing of a Diels-Alder covalent adaptable network with microparticle reinforcement

Presentation Date and Time
October 13, 2021 (Wednesday) 10:40

Track / Room
Track 3 / Meeting Room A-B

Authors (Click on name to view author profile)

1. Bischoff, Derek J. (University of Delaware, Materials Science and Engineering)
2. Mackay, Michael E. (University of Delaware, Materials Science and Engineering)
   Mackay, Michael E. (University of Delaware, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Derek J. Bischoff¹ and Michael E. Mackay^1,2
1Materials Science and Engineering, University of Delaware, Newark, DE 19716; ²Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716

Speaker / Presenter 
Bischoff, Derek J.

Keywords
additive manufacturing; composites; polymer melts

Text of Abstract
A limiting factor preventing the more widespread adoption of extrusion-based 3D printed parts is the relatively poor and anisotropic nature of their mechanical properties due to the inherent layer-by-layer, additive approach. Recently, covalent adaptable networks (CANs) have been used to produce nearly isotropic parts thanks to the thermoreversible, covalent bonds that make up the crosslinked network architecture. At temperatures experienced in the heated extrusion barrel, these bonds begin to either rapidly exchange or break into their monomeric form enabling flow and stress relaxation. The formation of covalent bonds across layers gives the thermoset-like network isotropic strength and a lack of void space in printed objects. In order to impart new properties or enhance mechanical properties, particle fillers can be added to a polymer matrix. In this work, spherical glass microparticles are compounded into a CAN matrix utilizing Diels-Alder chemistry for the first time. First unfilled CAN material is characterized and used in 3D printing to establish a baseline. Subsequently, bare microparticles are compounded into the matrix at varying volume fractions. The unique rheology of the microparticle-filled composites is used to evaluate the material for use in 3D printing. Due to the glassy and brittle nature of the materials at room temperature, a pellet-based printer is used in the printing process that avoids issues with typical filament-based printers. In the future, surface functionalization of the particles will enable thermoreversible bonds to form between the filler and matrix, thus facilitating the transfer of stress more effectively.