Unraveling the structure-properties correlation in thermal insulating and mechanically stiff PLA aerogels

Abstract

In this study, the relationship between the porous structure of polylactic acid-based (PLA) aerogels and their thermal insulation performance have been studied in detail. Different polymer contents were used for the fabrication of these aerogels leading to a wide range of low densities (36–167 kg/m³), porosities over 86 % and high crystallinity degrees (63–69 %). Their nanofibrillar structures led to high specific surface areas (79–91 m²/g), thin fibers (105–340 nm), and small pores (658–3140 nm). The mechanical performance and thermal insulating behavior have been deeply investigated, analyzing the involved mechanisms. The produced aerogels showed high stiffness with elastic modulus from 0.15 MPa to 12.82 MPa and compressive strengths of up to 540 kPa, significantly higher values than the traditional insulating materials, combined with remarkably low thermal conductivity values between 34.83 and 27.11 mW/m∙K, the lowest value found for PLA of aerogels to date. In addition, thermal conductivity was modeled, and the contributions of the different heat transfer mechanisms were calculated. The obtained results have been related to the different PLA aerogel samples and structural characteristics, obtaining a deep understanding of the relationship between the production process, porous structure, and the final mechanical and thermal insulating performance.