Solid-state foaming of biodegradable polyesters by means of supercritical CO₂/ethyl lactate mixtures: Towards designing advanced materials by means of sustainable processes

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• 作者：Aurelio Salerno ; Ugo Clerici ; Concepci贸n Domingo
• 关键词：Ethyl lactate ; Polyesters ; Solid-state foaming ; Supercritical CO2
• 刊名：European Polymer Journal
• 出版年：February, 2014
• 年：2014
• 卷：51
• 期：Complete
• 页码：1-11
• 全文大小：2534 K

文摘

In this work, a clean and sustainable approach for the design and manufacture of biodegradable foams with controlled pore structures is reported. Porous polycaprolactone (PCL), polylactic acid (PLA) and poly(L-lactide/caprolactone) (PLC) homo- and co-polymers have been prepared by a supercritical solid-state foaming technique. The process has been carried out at low temperature, in the range of 35-40 掳C, and at the pressure of 20 MPa. Supercritical CO₂ (scCO₂), pure or with a 0.2% molar fraction of ethyl lactate (EL), has been selected as the blowing agent. Foaming has been induced by a pressure quench approach and by using either a low (0.5 min) or a high (6 min) depressurization time. Results showed that blowing agent uptake and foaming was strongly affected by the thermal properties and crystalline structure of the polymers. Furthermore, adding a small amount of EL to scCO₂ decreased the plasticization temperature of the polymeric materials, finally improving foams uniformity and polymer foaming. Hence, homogeneous foams could be manufactured avoiding the use of toxic chemicals and at a temperature as low as 35 掳C for PLA and PLC, and as low as 40 掳C for the more crystalline PCL.