Effect of UV irradiation on PAN precursor fibers and stabilization process

Abstract

A low-cost rout for modifi cation the polyacrylontrile(PAN) precursor fi bers was developed. The approach involved pretreatment PAN precursor fibers with UV irradiation for various periods of time before the fibers were stabilized. The effect of UV irradiation on the chemical structure, orientation factor, density, crystallite size and morphology of the fi bers in the process of stabilization was characterized by use of fourier transform infrared spectroscopy(FTIR), fl oat-sink procedure, X-ray diffraction(XRD), scanning electron microscope(SEM), respectively. The results showed that UV irradiation could increase the density of the fi bers in stabilization process. FTIR analysis indicated that the cyclization of nitrile groups was initiated at room temperature by UV irradiation. The transformation of C≡N groups to C=N ones was accelerated in the process of stabilization. The orientation factor of irradiated fi bers was also increased. The crystallite size was decreased at fi rst and increased later, and the better irradiation time of UV was 3 min according to the XRD test. SEM analysis indicated that irradiation could decrease the internal and surface defects of the stabilized fi bers treated at 300 ℃.

Highly crosslinked layer-by-layer polyelectrolyte FO membranes: Understanding effects of salt concentration and deposition time on FO performance

“…From Table 3, it can also be seen that the first layer thickness L 1 of the LbL films is about 30-40 nm, which is a typical thickness for 3 bilayers LbL film prepared from PAH and PSS polyelectrolytes under 1 M NaCl deposition solutions [34,47]. It is interesting that L 1 increases to a small extent after UV irradiation, which is because PAN substrate can possibly be crosslinked by UV [50] that slightly increases the thickness of the dense layer. As a consequence, the resultant membranes after UV irradiation shows a decrease in reverse salt flux.…”

“…13). It could be assigned to the -CQN stretching vibration of PAN which occurs after crosslinking [50]. The existence of crosslinked PSS after UV irradiation can be proven by the decrease in the intensity of the -C-H stretching vibrations of the -CH 2 group at 2860 and 2935 cm À 1 , and the -CH associated with styrene group at 2900 cm À 1 (see Fig.…”

Switching Anionic and Cationic Semipermeability in Partially Hydrolyzed Polyacrylonitrile: A pH-Tunable Ionic Rectifier

“…30,31 Surface activation processes have been developed to create reactive sites on PAN interfaces for further grafting and/or immobilization. 32,33 Reactive groups on a PAN surface can be generated by UV irradiation, 34 plasma treatment, 35 metal ions activation, 36 or by hydrolysis. 37 Hydrolysis is important as it gives possibilities for further modification.…”

“…Polyacrylonitrile (PAN) membranes have attracted much attention because of a variety of excellent characteristics, which include thermal stability, tolerance to most solvents, and commercial availability. , Surface activation processes have been developed to create reactive sites on PAN interfaces for further grafting and/or immobilization. , Reactive groups on a PAN surface can be generated by UV irradiation, plasma treatment, metal ions activation, or by hydrolysis . Hydrolysis is important as it gives possibilities for further modification.…”