A two-step debinding process, consisting of solvent debinding followed by thermal debinding has been demonstrated as an effective method for removing binders from green parts produced by powder extrusion printing. However, the organic solvents typically used in solvent debinding are often flammable, carcinogenic, and environmentally harmful. To address this issue, this study introduced a water-soluble binder system composed of polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), and ethyl vinyl acetate (EVA), specifically designed for fabricating silicon carbide (SiC) ceramic green parts via PEP. During water-based debinding, a large amount of PVA was removed, leaving micro-pores in the green part. These pores served as channels for the remaining binder to escape during thermal debinding. Subsequent processing involving phenolic resin impregnation and pyrolysis (PRIP), followed by liquid silicon infiltration (LSI), resulted in Si/SiC ceramics with a density of 2.83 ± 0.09 g/cm³ and a strength of 279.5 ± 8.4 MPa.
Single-component blocked polyurethane (BPU) elastomers have garnered significant interest in three-dimensional (3D) printing due to their controllable reactivity, environmental friendliness, and storage stability. However, their extremely slow curing rates significantly limit practical applications. Existing 3D printing strategies primarily incorporate additional components to enhance material printability, which increases formulation complexity, fails to fundamentally address the issue of slow curing, and in some cases compromises mechanical properties. To address this challenge, we develop an ultrafast-curing BPU (UBPU) elastomer through reactivity-optimized formulation design, achieving additive-free processing. The UBPU system attains a gelation time of approximately 3.15 min at the deblocking temperature, representing a 28.6-fold faster curing rate relative to conventional BPU systems. The UBPU also demonstrates a high evaporation rate of the blocking agent. Accordingly, we propose a progressive curing-enabled extrusion printing (PCEEP) method, wherein the UBPU elastomer is preheated in extruder to further accelerate blocking agent evaporation during layer-by-layer deposition, thereby enabling the rapid stabilization of printed structures. This enhanced evaporation mechanism improves tensile strength of as-printed UBPU parts by 2-fold compared to cast-molded counterparts. Our study provides an additive-free strategy and novel insights into high-performance thermosetting polyurethane (TSPU) elastomers for advanced 3D printing applications.
危险品化学品经营许可证（带存储）