Lunar Regolith Simulant–Filled High-Performance Thermoplastic Composites for Lunar Construction and Their Potential for Additive Manufacturing

The use of lunar regolith (LR) for lunar construction is a key route to reducing the mass of materials transported from Earth. In this work, highly filled composites based on polyphenylsulfone (PPSU) with Tg = 219.1 °C and modified polyetherimide (PEI) with Tg = 247.1 °C containing up to 92.5 wt.% of LR simulant were prepared by dry blending the LR simulant and the polymer powders, followed by hot pressing. Their internal structure, mechanical, thermal, thermomechanical, and melt/flow properties were evaluated. The properties of the composites strongly depended on the LR simulant content and were governed by two competing mechanisms: restriction of polymer-chain mobility and of matrix deformation by the rigid mineral filler at moderate LR simulant contents, and increased porosity and loss of matrix continuity caused by binder deficiency at excessive filler loadings. At LR simulant contents of up to 60 wt.% for PPSU and 85 wt.% for PEI, dense, low-porosity (<10 vol.%) monolithic composites were formed, whereas higher filler loadings led to binder deficiency and increased porosity. LR simulant incorporation increased Shore D hardness from 75 to 88 for PPSU- and from 86 to 96 for PEI-based composites. Maximum compressive strength/modulus reached 122 MPa/6.3 GPa for PPSU- and 193 MPa/7.4 GPa for PEI-based composites, compared with 93 MPa/2.3 GPa and 150 MPa/3.3 GPa for neat polymers, respectively. Thermal conductivity increased to 0.64 and 0.72 W/(m·K), while CLTE decreased to 14.2 × 10−6 K−1 and 10.1 × 10−6 K−1 for PPSU- and PEI-based composites, respectively. Composites containing 50–60 wt.% of LR simulant retained melt/flow capability, indicating their potential suitability for processing by melt extrusion and additive manufacturing. Based on the obtained data, recommendations were formulated for application of the developed composites in melt-based 3D printing of complex-geometry parts and hot-pressed simple-shape construction elements.