Open AccessAmorphous Polymers’ Foaming and Blends with Organic Foaming-Aid Structured Additives in Supercritical CO2, a Way to Fabricate Porous Polymers from Macro to Nano Porosities in Batch or Continuous Processes
Author(s) -
Margaux Haurat,
Michel Dumon
Publication year - 2020
Publication title -
molecules/molecules online/molecules annual
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 149
eISSN - 1433-1373
pISSN - 1420-3049
DOI - 10.3390/molecules25225320
Subject(s) - materials science , polymer , porosity , supercritical fluid , extrusion , methyl methacrylate , foaming agent , chemical engineering , blowing agent , amorphous solid , nano , porous medium , copolymer , composite material , organic chemistry , chemistry , polyurethane , engineering
Organic polymers can be made porous via continuous or discontinuous expansion processes in scCO 2 . The resulting foams properties are controlled by the interplay of three groups of parameters: (i) Chemical, (ii) physico-chemical, and (iii) technological/process that are explained in this paper. The advantages and drawbacks of continuous (extrusion, injection foaming) or discontinuous (batch foaming) foaming processes in scCO 2 , will be discussed in this article; especially for micro or nano cellular polymers. Indeed, a challenge is to reduce both specific mass (e.g., ρ < 100 kg·m -3 ) and cell size (e.g., average pore diameter ϕ average pores < 100 nm). Then a particular system where small "objects" (coreshells CS, block copolymer MAM) are perfectly dispersed at a micrometric to nanometric scale in poly(methyl methacrylate) (PMMA) will be presented. Such "additives", considered as foaming aids, are aimed at "regulating" the foaming and lowering the pore size and/or density of PMMA based foams. Differences between these additives will be shown. Finally, in a PMMA/20 wt% MAM blend, via a quasi one-step batch foaming, a "porous to nonporous" transition is observed in thick samples. A lower limit of pore size (around 50 nm) seems to arise.