Effect of Foaming Agent Types and Content on Polylactic Acid Foam Materials Prepared by Fused Deposition Modeling

ABSTRACT The integration of foaming technology with fused deposition modeling (FDM) presents a viable approach for lightweight manufacturing. This study explores the influence of azodicarbonamide (AC) and thermally expandable microspheres (TEM) on the foaming behavior and properties of polylactic acid (PLA) fabricated via fused deposition modeling (FDM). The effects of the two foaming agents on density, cell structure, crystallization, and mechanical performance were systematically investigated. The research reveals that TEM achieves a maximum expansion rate of 33%, resulting in pores that are round and evenly distributed, with an average pore size exceeding 45 μm. In contrast, AC reaches only a 24% expansion rate, with smaller pores that tend to merge and rupture, and an average pore size below 30 μm. While both foaming agents negatively affect tensile strength, they both enhance impact strength. The specific tensile strength of both B‐AC and B‐TEM systems decreased compared to the PLA‐Blend, yet they exhibited similar values of approximately 26 MPa/(g/cm 3 ) at comparable densities. The AC system achieves an 84% increase in impact strength, reaching 6.22 J·m/kg (at 1.5 phr), while the TEM system results in a 32% improvement, reaching 4.46 J·m/kg (at 2.5 phr). Differential scanning calorimetry results confirmed that AC increases the crystallinity of PLA composites from 14.8% to 29.4%, whereas TEM has no significant effect on crystallinity. The increase in crystallinity indicates that the molecular chains are arranged in a more orderly manner, enhancing the mechanical stability of the B‐AC foam material. Thermogravimetric analysis further revealed distinct decomposition behaviors: AC exhibited a sharp decomposition peak around 223°C–233°C, contributing to rapid gas release and fine cell nucleation, while TEM showed a broad and delayed decomposition profile, favoring uniform cell growth. Furthermore, the fabrication of an aircraft model validated the lightweight potential of PLA foams. These findings provide guidance for tailoring PLA foams via FDM and highlight opportunities for integrating foaming with 3D printing in other thermoplastic systems.