Cryogenic treatment

Among the separadon tedmiques iodustrially implemented in this case are absorption and cryogenic separation. Adsorption according to the PSA process described above (see Secdon l.i.1.2) can also be applied, but is only economically viable for feedstock CO contents under 40 percent, or preferably 20 per cent This gives an effluent whose carbon monoxide concentration does not exceed or 80 per cent, althoi the yield of the operation is very hi (over 99 per cent). Cryogenic treatment is necessary for higher purities. 

In this section, after a brief discussion of the principal categories of PVA physical hydrogels in general, the PVA hydrogels obtained by cryogenic treatments are treated in detail. 

Coarsening of the dense and diluted regions imprinted by the cryogenic treatment, occurring at room temperature... 

Indeed, nonionic HEC, (hydroxypropyl)methylceUulose (HPMQ, methylcellu-lose (MC), and cationic 2-hydroxyethylcellulose can be crosshnked via UV irradiation assisted by the cryogenic treatment (Table 1). 

Pazos V, Mongrain R, Tardif J (2009) Polyvinyl alcohol cryogel optimizing the parameters of cryogenic treatment using hyperelastic models. J Mech Behav Biomed Mater 2 542-549... 

The health care industry has many possible applications for cryogenics. In 2005, Texas A M University Health Science Center-Baylor College of Dentistry investigated the effect of cryogenic treatment of nickel-titanium on instruments used by dentists. Past research had been conducted on stainless-steel endodontic instruments with no significant increase in wear resistance. This research demonstrated an increase in microhardness but not in cutting efficiency. 

Morariu Simona, Bercea Maria, and Brunchi Cristina-Eliza. Effect of cryogenic treatment on the rheological properties of chitosan/polylvinyl alcohol) hydrogels. Ind. Ene. Chem. Res. 54 no. 45 (2015) 11475-11482. 

---