Investigation of the damping properties of polylactic acid-based syntactic foam structures

Abstract

Nowadays, environmental awareness is more and more important. Therefore, the importance of weight reduction and creating a circular economy has increased. In this study, we foamed bio-based polylactic acid (PLA) with thermally expandable microspheres to create homogenous, compostable polymer foams. The polylactic acid-based foamed sheet samples were produced with a flat sheet extruder at 190 °C. We investigated the temperature-dependent mechanical properties of the samples—they show maximum damping capacity in the glass transition region. We also examined the frequency-dependent properties of the foamed samples and successfully extended these properties with the time-temperature superposition principle, to broaden the potential field of application of the foams. The damping properties of homogeneous, closed-cell foam structures produced with thermally expandable microspheres increased in the range of 0.1–20 000 Hz as a function of foaming agent content. We also produced foamed sheets from PLA/PBAT (polybutylene succinate) blends. The storage modulus of unfoamed reference samples showed a decreasing tendency. The tanδ of foamed systems containing only PLA or PBAT increased. The tanδ of foamed blends decreased in 25%/75% and 50%/50%PBAT/PLA systems, except for the 75%/25%PBAT/PLA blend. Therefore, PBAT/PLA blends can only be used to improve the damping ability of foamed samples above 75 wt% PBAT.

Keywords

• Damping
• Syntactic foam
• Polylactic acid
• Extrusion
• Physical blowing agent