Valorizing Biopolyester\nSuberin: Modification of Cellulose\nNanocrystals and Performance Assessment in 3D-Printed Biobased Acrylates

Suberin, a common biomass processing waste, is a complex\nbiopolymer\nand a promising source for the biorefinery of chemicals. Six different\napproaches for the extraction of birch outer bark suberin fatty acids\n(SFAs) were explored, and their application in grafting the surface\nof cellulose nanocrystals (CNCs) was investigated. Successful CNC\nfunctionalization was controlled with FTIR and NMR analyses. In-depth\nresearch allowed us to evaluate the interface of the nanocellulose\nand polymer matrix. Three structurally distinct SFA-grafted CNCs were\nintegrated into a vegetable oil-based acrylate resin in an ultralow\nconcentration of 0.1 wt %. Five biobased acrylic resin formulations\nwere prepared: without reinforcement, with CNC, and with three distinct\nSFA-grafted CNCs. Vat photopolymerization (VP) 3D printing was utilized\nfor sample preparation. The effects of grafted CNC components on 3D-printed\nsamples’ thermal stability, thermomechanical properties, and\nwettability were evaluated in detail. CNC functionalization enhanced\nthe interface with the polymer matrix, yielding up to a 2-fold increase\nin elongation and up to a 2.5-fold increase in strength in tensile\nand flexural tests compared to the polymeric matrix. The CNC-SFA-modified\nfiller demonstrated performance comparable to, or even better than,\npetroleum-based chemical modification routes found in the existing\nliterature. This study highlights a promising approach for green functionalization\nof CNCs and verifies its use in interface enhancement using a biobased\nacrylate matrix.