Photo-Curing 3D Printing of Highly Deformable Palm Oil-Based Thermosets with Soft Fatty Acid Chain Entanglement

Photo-curing three-dimensional (3D) printing technology is normally used for the manufacture of covalently cross-linked thermosets due to its high efficiency and resolution. However, printed thermosets are mostly derived from petroleum resources and tend to be highly brittle and poorly deformable. Herein, renewable palm oil (PO) was used to fabricate highly robust and deformable bio-based thermosetting networks with an intrinsic soft phase assembled by long fatty acid chains via a liquid crystal display 3D printing technique. A PO-based methacrylate (MPOEA) with two C═C bonds and a fatty acid chain was synthesized via an amidation and esterification strategy. Isobornyl acrylate (IBOA) with a stiff alkyl ring was selected as a comonomer for MPOEA to form photosensitive MPOEA-IBOA inks. The printed MPOEA-IBOA networks possessed a satisfactory combination of the cross-linking density, the molecular distance between cross-linking points, and the soft phase distributed in the matrix. Therefore, the optimally designed thermosets exhibited a tensile strength of 52.1 MPa, a fracture elongation of 8.2%, a flexural strength of 57.3 MPa, a flexural deflection of 34.6 mm, a Tg of 105.1 °C, and excellent shape memory behavior. The formation mechanism of the fatty acid chain soft phase and its effects on the UV-initiated curing rate, gel content, dynamic mechanical property, thermal stability, and micromorphology of the MPOEA-IBOA polymer were fully investigated.