Photo‐Curing 3D Printing of Thermosetting Sacrificial Tooling for Fabricating Fiber‐Reinforced Hollow Composites

Self-healing materials are the current focus of smart materials research. However, the implementation of self-healing materials remains limited by the challenge of balancing efficient healing properties with high mechanical strength. In this study, N, N′-(4-hydroxy-3-methoxybenzyl) aniline (VPSB) with π−π conjugated structures were prepared by introducing Schiff base bonds between aromatic rings. VPSB is then incorporated into the polyurethane system to synthesize a self-healing waterborne polyurethane vitrimer (VPSB-WPU) containing conjugated aromatic Schiff base bonds. This locally conjugated structure can convert absorbed visible light into thermal energy, which promotes the rapid breaking and formation of Schiff base bonds, resulting in an improved selfhealing effect. The results indicated that the topological network of the vitrimer exhibited an activation energy (E a ) of 60.69 kJ/mol and a freezing transition temperature (T v ) of 45.46 °C. After 3 min of visible-light irradiation, the film temperature increased from 6.4 to 91.5 °C, with a photothermal conversion efficiency of 92.13% and a film scratch-healing efficiency of 93.75%. After 25 min of irradiation, the fractured film's tensile strength after healing was 11.57 MPa. These results demonstrated that VPSB-WPU exhibited vitrimer properties and possessed excellent mechanical strength, photothermal conversion, and self-healing function. A balance between highly efficient healing properties and excellent mechanical strength was achieved by the VPSB-WPU vitrimer, making it highly promising for future applications in material self-healing.

Section: Methodsmentioning

confidence: 99%

“…Subsequently, the prepared VPSB-WPU film was placed in a 100 °C oven for a period of 2 h, during which a thermal postcuring process was implemented. 43 Figure S2a,b shows the efficiency of the conversion of the C = C double bonds during curing process.…”

Section: Preparation Of the Uv-curable Vpsb-wpu Vitrimermentioning

confidence: 99%

A Highly Effective Self-Healing Waterborne Polyurethane Vitrimer Containing Conjugated Schiff Base Bonds Driven by Photothermal

Tan,

Zhao,

Zhang

et al. 2024

“…This process helps consume incompletely reacted monomers and enhances the mechanical properties of the prints. 63 Additionally, the dynamic exchange reaction of hindered urea bonds with rigid chain extenders (PACM, IPDA, and MOCA) forms stronger hydrogen bonding, resulting in a polymer network with a more rigid structure. This results in the formation of a dense reticulation structure, increasing the mixing degree of the urethane molecule's soft and hard chain segments.…”

Section: Effect Of Different Thermal-curing Temperatures On the Mecha...mentioning

confidence: 99%

Synthesis and Characterization of Silicon-Modified Polyurethane Acrylate for UV-Thermal Dual Curing in Three Dimensional Printing

Wu,

Ding,

Yuan

et al. 2024

Single UV-curing silicone-modified polyurethane acrylate materials have limitations, such as low molecular polymerization and weak mechanical properties compared to thermal-curing materials. This experiment synthesized a polyurethane prepolymer coated with isocyanate groups using hydroxyl polyether silicone oil (PDMS) and diisocyanate. tert-Butylaminoethyl methacrylate (t-BAEMA) was then utilized to create a silicon-modified polyurethane acrylate (SiBPUA) prepolymer with heat-unstable urea and photosensitive groups. This prepolymer was incorporated into photosensitive resin materials and processed through 3D DLP 3D printing. Upon heating, the −NCO group regenerated, and the chain extender underwent a secondary curing reaction, increasing molecular weight and improving performance. The study investigated the impact of different reactants on SiBPUA properties, deblocking temperature, optimal curing temperature, and enhancement of UV-curing materials through thermal curing. The results revealed that the use of isophorone diisocyanate (IPDI), 4,4′-diaminodicyclohexylmethane (PACM), and methyl methacrylate (MMA) resulted in the best mechanical properties. Furthermore, UV-thermal dual curing significantly enhanced tensile strength (12.5 MPa) and elongation at break (219.5%), broadening the application potential of UV-curing 3D printing materials.

“…Zhang and co-workers developed a polythiourethane cross-linker and used the resulting 3D CAN in self-heling and shape memory applications . Similarly, 3D-printed sacrificial scaffolds and recyclable resins have been developed using acetal , and hindered urea − -based CANs.…”

Section: Introductionmentioning

confidence: 99%

3D Printing of Vinylogous Urethane-Based Methacrylic Covalent Adaptable Networks by Vat Photopolymerization

Ballester-Bayarri,

Pascal,

Ayestaran

et al. 2024

Covalent adaptable networks (CANs) have the potential to combine the excellent mechanical properties of traditional thermoset materials with the reprocessability of traditional thermoplastics. However, the processing of CANs using common techniques for thermoplastics has proven challenging. In this work, the 3D printing of reprocessable CANs with controlled shape is reported using vat photopolymerization (VP). Using a vinylogous urethane-containing methacrylic cross-linker, a series of resins containing nonreactive and reactive diluents are described. The resin viscosity can be easily tuned by the relative amount of diluent to functional cross-linker such that the viscosity of commercial resins can be easily achieved. By studying the curing kinetics using Jacob's equation, optimal printing conditions are found that allow for highresolution printing with limited shrinkage. In addition, due to the presence of dynamic bonds in the final material, it is shown that the final printed piece can be reprocessed at high temperatures and can even be recycled into a second-generation resin that can be reprinted.