Application of poly(lactic acid)-grafted cellulose nanofibers as both inhibitor and reinforcement for 3D-printable tough polydicyclopentadiene composites via frontal ring-opening metathesis polymerization

Due to the contradiction between curing rate and degree of polymerization, fabrication of 3D-printable thermosetting polymer resin with strong, and tough properties via frontal ring-opening metathesis polymerization (FROMP) remains challenging. Here, poly(lactic acid)-grafted cellulose nanofibers (CNF-g-PLA) was used as both inhibitor and fortifier to prepare 3D printable, strong, and tough polydicyclopentadiene (PDCPD)-based composites by FROMP. When 5 % CNF-g-PLA was added, the fracture toughness and tensile strength of the PDCPD/CNF-g-PLA composites increased by 277.94 % and 12.6 %, respectively. Meanwhile, the rate of radical-induced polymerization was reduced by 106 %, significantly improved the 3D-printability of PDCPD. The two-dimensional (2D) sheet of PDCPD/CNF-g-PLA composites exhibited good flexibility, which could easily be crimped into a cylinder because of CNF-g-PLA contribution. Moreover, owing to the improved toughness, PDCPD/CNF-g-PLA composites can be used as engineering protect materials such as vehicle bumpers, further broadening the application fields of 3D-printed PDCPD/CNF-g-PLA composites. This study provides a feasible method for the application of CNF in 3D printable thermoset resins.