Application of compressed carbon dioxide in the incorporation of additives into polymers

Abstract

SYNOPSISIt has been found that carbon dioxide remarkably accelerates the absorption of many low molecular weight additives into a number of glassy polymers. This effect is due to the high diffusivity, solubility, and plasticizing action of compressed COP in polymers. The transport of CO, and the effects of CO, pressure on the transport of other low molecular weight compounds in polymers have been studied by a simple gravimetric method Polymer film samples were contacted in a pressure vessel with compressed CO,, or with COP plus various organic liquids or solids, and the sample weight was followed with a fast-response electronic balance during subsequent desorption at atmospheric pressure. Upon release of the pressure, absorbed CO, rapidly diffuses from the polymer, while the other compounds desorb much more slowly. The amount of additive absorbed can be determined from the plateau weight of the sample after most of the CO, has escaped. Extensive kinetic and equilibrium data are reported for the model system poly (vinyl chloride)/dimethyl phthalate/CO,, and a number of other examples of C0,-assisted additive absorption are given. This "infusion" process, in effect, amounts to the partitioning of the additive between the COz-and polymerrich phases; consequently, the relative solubility of the additive in CO, and in the polymer is a major factor governing the amount of additive absorbed. Data reported here illustrate the generality and potentially broad applicability of C0,-assisted polymer impregnation.

Supercritical solvent impregnation of poly(ɛ-caprolactone)/poly(oxyethylene-b-oxypropylene-b-oxyethylene) and poly(ɛ-caprolactone)/poly(ethylene-vinyl acetate) blends for controlled release applications

“…This effect is contrary to the favourable plasticization effect and can increase the final relative crystallinity of the processed polymeric materials, thus influencing negatively the overall impregnation efficiency [9,12,[33][34][35][36]. However, we did not measure the relative crystallinity of the employed materials after scCO 2 and scCO 2 +cosolvent processing and therefore we did not know if crystallinity increased or decreased.…”

“…Moreover, scCO 2 induced crystallization of polymeric substrates can also influence the overall supercritical solvent impregnation process as well as the final relative crystallinity of the processed polymeric materials [9,12,[33][34][35][36].…”

Bone tissue engineering therapeutics: controlled drug delivery in three-dimensional scaffolds

“…Impregnation using supercritical fluid technologies has the advantage of using a supercritical fluid with high diffusivity in the polymer chosen in addition to its high solubility and plasticizing capability (Berens et al 1992;Kazarian 2000;Duarte et al 2007). Electrospinning is another technique with a potential to develop bioactive three-dimensional bone scaffolds with drug-release capabilities (Li, W. et al 2002;Matthews et al 2002;Ma et al 2005;Gupta et al 2007).…”

Surface properties and depth analysis of polyethylene/polydimethylsiloxane composite prepared by using supercritical carbon dioxide

“…It is considered that increasing the initial pressure and changing the side chain of D4 will increase the solubility of the monomer in scCO 2 . [20][21][22][23][24] The amount of impregnated low-molecular-weight components also depends on the soaking time and it attains an Figure 1 Synthetic scheme for preparation of PDMS.…”