| Autor: |
Hamachi LS; Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.; Department of Chemistry and Biochemistry, California Polytechnic State University, San Luis Obispo, California 93407, United States., Rau DA; Department of Mechanical Engineering, Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States., Arrington CB; Department of Chemistry, Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States., Sheppard DT; Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States., Fortman DJ; Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.; Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853, United States., Long TE; School of Molecular Sciences, Biodesign Center for Sustainable Macromolecular Materials and Manufacturing, Arizona State University, Tempe, Arizona 85281, United States., Williams CB; Department of Mechanical Engineering, Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States., Dichtel WR; Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States. |
| Abstrakt: |
Relative to other additive manufacturing modalities, vat photopolymerization (VP) offers designers superior surface finish, feature resolution, and throughput. However, poor interlayer network formation can limit a VP-printed part's tensile strength along the build axis. We demonstrate that the incorporation of carbamate bonds capable of undergoing dissociative exchange reactions provides improved interlayer network formation in VP-printed urethane acrylate polymers. In the presence of dibutyltin dilaurate catalyst, the exchange of these carbamate bonds enables rapid stress relaxation with an activation energy of 133 kJ/mol, consistent with a dissociative bond exchange process. Annealed XY tensile samples containing a catalyst demonstrate a 25% decrease in Young's modulus, attributed to statistical changes in network topology, while samples without a catalyst show no observable effect. Annealed ZX tensile samples printed with layers perpendicular to tensile load demonstrate an increase in elongation at break, indicative of self-healing. The strain at break for samples containing a catalyst increases from 33.9 to 56.0% after annealing but decreases from 48.1 to 32.1% after annealing in samples without a catalyst. This thermally activated bond exchange process improves the performance of VP-printed materials via self-healing across layers and provides a means to change Young's modulus after printing. Thus, the incorporation of carbamate bonds and appropriate catalysts in the VP-printing process provides a robust platform for enhancing material properties and performance. |
