Hydroperoxide formation in the early stages of polypropylene photo-oxidation

The total chemiluminescence from polypropylene films heated in an inert atmosphere is a sensitive measure of the hydroperoxide content in the induction period of photo-oxidation. The examination of the hydroperoxide content in unstabilised film melt-pressed from the powder, stabilised melt-pressed film and a commercial stabilised film all show a very rapid increase in the hydroperoxide content in the early stages of photo-oxidation which could not be detected by ATR-IR or XPS analysis. This appears as a peak in all of the films which increases in area with film thickness, indicating that it is a bulk property. While stabilisers may inhibit the photo-oxidation as measured by carbonyl index, they cannot prevent this early buildup and decay of hydroperoxides. These are believed to form by the rapid oxidation of the polypropylene in localised zones of high photoinstability. The peak in hydroperoxide content is a consequence of the kinetics of the consecutive reaction of hydroperoxide formation and photolysis which leads to secondary oxidation products and subsequent slower photo-oxidation

The effect of stabilisers on integrated chemiluminescence in the early stages of polypropylene photo-oxidation

The integrated chemiluminescence obtained by heating photo-oxidised polypropylene films in an inert atmosphere is affected by a number of common stabilisers, particularly free radical scavengers, such as hindered phenols, and hydroperoxide decomposers, such as thiodipropionate esters. These stabilisers must be removed prior to chemiluminescence analysis of the hydroperoxide content in the early stages of photo-oxidation. From an analysis of the effect of stabilisers on the peak in hydroperoxide concentration observed after short times of UV irradiation with wavelengths longer than 300 nm, it was found that only the thiodipropionate ester and a 2-hydroxybenzophenone UV absorber affected the kinetics of hydroperoxide formation and decomposition and increased the induction period as measured by carbonyl index. A hindered triphenyl phosphite produced an immediate increase in integrated chemiluminescence and was a pro-degradant unless a hindered phenol was incorporated to inhibit peroxy radical attack on the stabiliser. A commercial hindered piperidine caused a lowering of the chemiluminescence when the sample was heated for analysis, consistent with a weak radical scavenging and hydroperoxide-decomposing activity of the amine, but did not affect the kinetics of formation and decomposition of hydroperoxides on UV irradiation

Adsorption of heavy metal ions and azo dyes by crosslinked nanochelating resins based on poly(methylmethacrylate-co-maleic anhydride)

Chelating resins are suitable materials for the removal of heavy metals in water treatments. A copolymer, Poly(MMA-co-MA), was synthesized by radical polymerization of maleic anhydride (MA) and methyl methacrylate (MMA), characterized and transformed into multifunctional nanochelating resin beads (80–150 nm) via hydrolysis, grafting and crosslink reactions. The resin beads were characterized by swelling studies, field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). The main purpose of this work was to determine the adsorption capacity of the prepared resins (swelling ratio ~55%) towards metal ions such as Hg2+, Cd2+, Cu2+ from water at three different pH values (3, 6 and 9). Variations in pH and types of metal ions have not significantly affected the chelation capacity of these resins. The maximum chelation capacity of one of the prepared resin beads (Co-g-AP3) for Hg2+ was 63, 85.8 and 71.14 mg/g at pH 3, 6 and 9, respectively. Approximately 96% of the metal ions could be desorbed from the resin. Adsorption capacity of these resins towards three commercial synthetic azo dyes was also investigated. The maximum adsorption of dye AY42 was 91% for the resin Co-g-AP3 at room temperature. This insures the applicability of the synthesized resins for industrial applications

and NiO/CNTs Nanocomposite Modified Carbon Paste Electrode

The electrochemical activities of hydroxylamine (HX) as a pollutant compound at a 1,1-bis(phenylacetyl) ferrocenele/NiO/CNTs modified carbon paste electrode (1,1-BPF/NiO/CNTs/CPE) has been studied. 1,1-BPF was used as a suitable mediator for elecrocatalytic interaction with HX. The voltammetric properties of HX at the 1,1-BPF/NiO/CNTs/CPE was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry, and square wave voltammetry (SWV) methods. The oxidation peak current increases linearly with HX concentration in the range 0.5-250.0 mu M and the detection limit for HX was 0.2 mu M. The sensor was applied to wastewater samples with excellent performance