Additive Manufacturing and Characterization of Polystyrene for Thermal Insulation Applications

The energy-intensive residential sector critically requires sustainable and highly efficient thermal insulation solutions. Due to the increasing demand for complex-shaped parts, it remains challenging to give them insulating properties. Indeed, traditional processing methods for foam production offer limited control over the internal architecture, a key factor in performance. This paper aims to fill that gap by using Material Extrusion Additive Manufacturing (MEAM) as a new technique to produce tailored atactic Polystyrene components, leveraging additive manufacturing's ability to create complex geometries and control the internal structure (lattice)—capabilities that are usually restricted by traditional methods. Polystyrene is a favored material due to its lower thermal conductivity compared to other polymeric materials; however, conventional manufacturing processes, such as extrusion foaming or foam injection molding, are limited to standardized geometries and lack precise control over the internal cellular structure, a critical factor in determining thermal insulating capabilities. The MEAM process was optimized, revealing that a bed temperature above the glass transition temperature (Tg) is crucial for interlayer adhesion, while moderate printing speeds (e.g., 2200 mm/min) yielded the best mechanical performance. Thermal conductivity was found not to be linearly dependent on the infill density, showing a minimum of 0.03 W/(mK) at 25% infill density for the octahedral structure. Numerical simulations, validated against experimental heat flux data, confirmed the significance of natural convection within the air-occluded cells, supported by high Jeffreys’ numbers (∼105). The closed-cell structure obtained by MEAM positively contributes to thermal insulation by reducing the effects of natural convection within the cells. This work established MEAM as a promising pathway for fabricating structurally optimized insulators with performance that can rival or be tailored beyond traditional foams.