Post-irradiation free-radical reactions in poly(ethylene terephthalate)

Selective removal of Cr(VI) ions from aqueous solutions including Cr(VI), Cu(II) and Cd(II) ions by 4-vinyl pyridine/2-hydroxyethylmethacrylate monomer mixture grafted poly(ethylene terephthalate) fiber

In this study, a new reactively fibrous adsorbent was prepared by grafting 4-vinyl pyridine (4-VP) and 2-hydroxyethylmethacrylate (HEMA) monomer mixture onto poly(ethylene terephthalate) (PET) fibers for removal of Cr(VI), Cu(II) and Cd(II) metal ions from aqueous solution by using batch adsorption method. The influence of various parameters such as graft yield (GY), pH, adsorption time, initial ion concentration and adsorption temperature was investigated. The selectivity of the reactive fiber was also examined. The results show that the adsorbed amount of metal ions followed as given in the order Cr(VI)>Cd(II)>Cu(II). At pH 3, Cr(VI) was removed by 99% while the initial concentration of ions was at 5 mg L(-1) and by 94% at 400 mg L(-1). It was found that the grafted fiber is more selective for Cr(VI) ions in the mixed solution of Cr(VI)-Cu(II), Cr(VI)-Cd(II) and Cr(VI)-Cu(II)-Cd(II) at pH 3 and it was observed that the grafted fibers are stable and regenerable by acid and base without losing their activity.

Free radical decay kinetics in PMMA bone cement

Electron-spin resonance has been used to measure the decay of the concentration of polymerization radicals in polymethyl methacrylate (PMMA) bone cement and the kinetics of the decay determined. Thermal annealing at various temperatures has shown that the logarithm of the concentration of radicals varies linearly with time, but with a nonzero intercept. These results have been analyzed by including both first- and second-order decay processes. The first-order process has an activation energy of 39 +/- 2 kcal/mol and is probably due to a diffusion-limited termination. The second-order process has an activation energy of 36 +/- 5 kcal/mol and is probably due to bimolecular termination.