One thermoplastic PMMA/hollow glass microspheres syntactic foam: preparation, characterization, application and recycle

Syntactic foams are lightweight, high-strength materials widely employed in naval and aerospace applications. However, conventional syntactic foams based on non-recyclable thermosetting matrices pose significant environmental challenges, underscoring the urgent need for sustainable alternatives. In this study, a binary liquid resin comprising PMMA and MMA was employed as the matrix, with hollow glass microbeads (HGMs) incorporated as lightweight fillers. PMMA/HGM syntactic foams were fabricated via casting and compression molding. The effects of HGM content and particle size on foam density, polymerization behavior, and mechanical properties were systematically investigated. The syntactic foam containing 20 wt% HGMs (30 μm) exhibited outstanding specific strength, with specific tensile, flexural, and compressive strengths of 28.67, 60.78, and 123.85 MPa/(g/cm 3 ), respectively. Finite element analysis confirmed that HGMs play a crucial role in regulating the mechanical performance of the foams. The feasibility of utilizing PMMA/HGM syntactic foams as core materials for sandwich structures was further validated; the resulting sandwich panels demonstrated superior compressive performance, with flatwise and edgewise compressive strengths of 10.10 MPa and 25.16 MPa, respectively. Notably, the excellent recyclability of PMMA/HGM syntactic foams and corresponding sandwich panels was successfully demonstrated through dissolution in MMA, enabling efficient separation of the constituent components.