Three-Dimensional Printing of Shape Memory Composites with Epoxy-Acrylate Hybrid Photopolymer

Four-dimensional
printing, a new process to fabricate active materials
through three-dimensional (3D) printing developed by MIT’s
Self-Assembly Lab in 2014, has attracted more and more research and
development interests recently. In this paper, a type of epoxy-acrylate
hybrid photopolymer was synthesized and applied to fabricate shape
memory polymers through a stereolithography 3D printing technique.
The glass-to-rubbery modulus ratio of the printed sample determined
by dynamic mechanical analysis is as high as 600, indicating that
it may possess good shape memory properties. Fold-deploy and shape
memory cycle tests were applied to evaluate its shape memory performance.
The shape fixity ratio and the shape recovery ratio in ten cycles
of fold-deploy tests are about 99 and 100%, respectively. The shape
recovery process takes less than 20 s, indicating its rapid shape
recovery rate. The shape fixity ratio and shape recovery ratio during
18 consecutive shape memory cycles are 97.44 ± 0.08 and 100.02
± 0.05%, respectively, showing that the printed sample has high
shape fixity ratio, shape recovery ratio, and excellent cycling stability.
A tensile test at 62 °C demonstrates that the printed samples
combine a relatively large break strain of 38% with a large recovery stress of 4.7
MPa. Besides, mechanical and thermal stability tests prove that the
printed sample has good thermal stability and mechanical properties,
including high strength and good toughness.