A clean and sustainable route towards the design and fabrication of biodegradable foams by means of supercritical CO2/ethyl lactate solid-state foaming

Abstract

Polymeric foams are essential elements of our life as they are widely used for applications requiring light-weight materials coupled with good mechanical properties and controlled energy and mass transfer. However, foams are often made of petroleum-derivate non degradable materials and manufactured by means of toxic and often hazardous blowing agents. In this work, a clean and sustainable approach to design and fabricate porous biodegradable poly(ε-caprolactone) (PCL) materials via solid-state foaming is investigated. The foaming process was performed by using supercritical mixtures of carbon dioxide (CO₂) and ethyl lactate (EL) as non-toxic and environmentally friendly blowing agents. Operating temperatures, in the range of 35–40 °C, a small amount of EL (up to 0.2%) and either one or two step depressurization profiles were used to control PCL foaming. The results of this study demonstrate that supercritical CO₂/EL binary mixtures are promising safer and sustainable blowing agents to design and fabricate renewable PCL foams at relatively low temperatures and with density as low as 0.2 g cm⁻³, mean pore size in the 14–530 μm range and pore density from 3.9 × 10⁴ to 1.4 x 10⁸ pore cm⁻³.