Supercritical CO 2 ‐assisted extrusion foaming: A suitable process to produce very lightweight acrylic polymer micro foams

• Published in: Journal of applied polymer science 2023-01, Vol.140 (3)
• Main Authors: Haurat, Margaux, Sauceau, Martial, Baillon, Fabien, Barbenchon, Louise Le, Pedros, Matthieu, Dumon, Michel
• Format: Article
• Language: English
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.53277

A strategy of CO 2 ‐assisted extrusion foaming of PMMA‐based materials was established to minimize both foam density and porosities dimension. First a highly CO 2 ‐philic block copolymer (MAM: PMMA‐PBA‐PMMA) was added in PMMA in order to improve CO 2 saturation before foaming. Then the extruding conditions were optimized to maximize CO 2 uptake and prevent coalescence. The extruding temperature reduction led to an increase of pressure in the barrel, favorable to cell size reduction. With the combination of material formulation and extruding strategy, very lightweight homogeneous foams with small porosities have been produced. Lightest PMMA micro foams ( ρ  = 0.06 g cm −3 ) are demonstrated with 7 wt% CO 2 at 130°C and lightest blend micro foams ( ρ  = 0.04 g cm −3 ) are obtained at lower temperature (110°C, 7.7 wt% CO 2 ). If MAM allows a reduction of T foaming , it also allows a much better cell homogeneity, an increase in cell density (e.g., from 3.6 10 7  cells cm −3 to 2 to 6 10 8  cells cm −3 ) and an overall decrease in cell size (from 100 to 40 μm). These acrylic foams produced through scCO 2 ‐assisted extrusion has a much lower density than those ever produced in batch ( ρ  ≥ 0.2 g cm −3 ).