scCO2Supercritical Carbon Dioxide (extraction)
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A dispersion polymerization is one in which the monomer-initiator are soluble in the reaction medium, while the polymer formed is insoluble and the majority of effective CO2-soluble stabilisers for dispersion polymerisation in scCO2 have been fluorinated or silicone-based polymers [3].
[7] reported the first dispersion polymerization of N-vinyl-2- pyrrolidone (NVP) in scCO2 using a highly soluble initiator and silicon based surfactant.
In this paper, the dispersion polymerization of MMA was reported by using Clariant Nuva HPC as stabilizer in scCO2 [11].
The effect of reaction time on the polymerization of MMA were summarized in Table- 1 for dispersion polymerization of MMA in scCO2 using Clariant Nuva HPC.
However, polymerizations were carried out in scCO2 offer the advantage of increasing the diffusivity of monomers into the growing polymer particles to maintain a sufficient rate of propagation, which in turn effectively facilitates the gel effect.
Additionally, in scCO2 system, the smaller particles had a fewer number of radicals per particle, and less bimolecular termination was expected in the smaller particles than in the larger ones [16].
Since it converts to its supercritical (fluid) stage at a relatively low pressure and temperature, SCCO2 is ideal for materials that are heat-sensitive or reactive with other sterilization methods.
To deactivate spores as well as live bacteria, the company provides sheets of paper treated with a mix of chemical additives including an acid that can be dissolved into the supercritical SCCO2 sterilizing fluid, much like detergent in a washing machine.
SCCO2 sterilization slowly is gaining popularity and acceptance in the medtech industry, having been used to sanitize regenerative materials, biologic scaffolds and resorbable polymers ranging from poly-L-lactide and poly-D-lactide to L-lactide, DL-lactide and L-lactide/glycolide.
A legion of possibilities truly exists as the company attempts to branch into other sectors: Its SCCO2 technology already has infiltrated supranamics manufacturing, industrial degreasing, silicon wafer cleaning and textile dyeing.
tissue banks use SCCO2 to clean bone, tendon and other products; Australian Biotechnologies Pty.
In addition, the SCCO2 process--like gamma irradiation--can be performed while samples are sealed within their final packaging, reducing the opportunity for the reintroduction of contaminants.