Covalently functionalized cellulose nanocrystal-reinforced photocurable thermosetting elastomer for 3D printing application

Due to distinct advantages of 3D printing (3DP), multifunctional materials are swiftly finding their applications into diverse industries nowadays. Among the existing 3DP materials, polymers present vast and exciting opportunities but simultaneously face new challenges to satisfy certain specifications. Among the existing polymer classes, elastomers play an important role because of its wide range of applications in nearly every industry such as automotive, marine, aerospace, electronics, medical, and consumer. However, 3D printing of elastomers remains an exigent task because of the resulting weak mechanical properties that impede its proliferation to different industrial applications. In improving material properties, the use of nanofiller has been a widely accepted approach. In pursuit of global environmental sustainability, the trend nowadays is to identify a material from a biobased source. As a biobased filler with inherently high stiffness, high strength, and high aspect ratio, cellulose nanocrystal has the potential to impart high-performance reinforcement to 3D-printed elastomers and consequently satisfy end-use requirements. Notwithstanding its inherent characteristics, the inhomogeneous dispersion of CNC in an elastomeric matrix would cause detrimental effects on the structural integrity of the nanocomposite material. Earlier attempts of reinforcing stereolithography resins using CNC, pristine and modified, yield to a moderate increase in strength but greatly compromise the elongation at break of the composite material. Hence, this study first reports high toughness improvement of the 3D-printed photocurable elastomer via stereolithography using a covalently functionalized CNC. More so, it is interesting to note that percolation threshold of < 1 wt% has significant effects on the different mechanical properties of the new nanocomposite material. The morphological, thermal, and mechanical properties of the new nanocomposite material are delineated. The approach prescribed in this study presents an effective route to expand the utility of CNC to nonpolar matrices such as the thermosetting elastomer and to increase the biobased content of a 3DP material in achieving the global need for sustainable materials.