Ultrasonic-Assisted Preparation of Silanized Nanocellulose and Its Regulatory Effect on Mechanical–Thermal Properties of LCD 3D Printing Photosensitive Resin

Cellulose nanofibrils (CNFs), with their high aspect ratio, have been widely used in various resin-based composites. To address the issues of easy agglomeration and poor interfacial compatibility of CNFs in hydrophobic acrylate photosensitive resins, this study adopted γ-methacryloyloxypropyltrimethoxysilane (KH570) for silane modification of CNFs, comparing heating–ultrasonication and heating–stirring methods. Mechanical properties were tested via LCD 3D printer to print splines. FTIR, XRD, and SEM verified successful modification, with the silicon substitution degree of heating–ultrasonication modification reaching 29.35%, significantly higher than heating–stirring (22.76%). Thermal analysis showed the main decomposition temperature increased from 400 °C to 420 °C, while DMA confirmed improved rigidity and glass transition temperature. Mechanical tests revealed a strength–toughness trade-off: the 1 wt% modified CNF composite exhibited a tensile strength of 45.17 MPa (9.41 MPa higher than unmodified CNFs at the same dosage), while a high dosage (3.5 wt%) enhanced toughness but reduced strength. The ultrasound-assisted silanization reaction proposed in this study optimizes the preparation process, achieving dual improvements in modification efficiency and dispersion. In terms of performance regulation, it reveals the quantitative control rules and trade-off characteristics of modified CNF content on the mechanical–thermal properties of the composites, providing a basis for performance customization. This study provides a feasible strategy for CNF modification in photopolymerizable 3D printing composites, expanding nanocellulose’s application in additive manufacturing.