This paper presents the investigation work on different polymeric materials used as insulation materials of conductors in a multicore instrumentation cable. Among differently colored materials, only ...the white one presented cracks after a few years of use. Isothermal and non-isothermal DSC measurements were performed on initial (non-used) and aged (in service used or laboratory aged) materials as well as on raw materials in order to characterize their stability and the ageing state after storage, use in service or laboratory ageing. As shown by the oxidation induction time values, a pronounced antioxidant loss occurred for all materials during storage or service; plus a strong effect of the ambient light on stability was observed for the white insulation material. Around 3% of filler, consisting mainly of TiO
2 particles (as revealed by SEM-XRF elemental analysis), was found in the white material. The higher degradability of the white material can be related to both the photocatalytic effect of the TiO
2 particles and rapid loss of stabilizers.
The thermal degradation of some polyethylenes (one type of high density PE and two of low-density) was studied by isothermal chemiluminescence. Each polymer was stabilized by one of four phenolic ...additives:
p-
t-butylphenol (considered as reference), 2,4,6-tri-
t-butylphenol,
p-
t-butylcalix4arene, and
p-
t-butylcalix6arene. Six kinetic parameters of thermal oxidation (induction period, maximum oxidation rate, half-period of ageing, maximum CL intensity, maximum degradation time, and activation energy) along with relative activity and stability were calculated. Protection efficiency of additives was evaluated by relative activity and relative stability indexes. Considerations of a stabilization mechanism involving calixarenes are presented.
The stabilization effect of various carbon materials:
C60fullerene, three adducts with levopimaric acid, two sorts of carbon black and nanocarbon on HDPE, LDPE and LLDPE have been studied by ...chemiluminescence at 180, 190 and 200 °C. Kinetic parameters: oxidation induction time, rate of oxidation and activation energy were determined. On the basis of these results some considerations on oxidation prevention mechanism are revealed.
A chemiluminescence study on photo-irradiated isotactic polypropylene in the presence of three new HALS compounds, mercapto-1,3,5-triazinic phenolic stabiliser (antioxidant T) and Tinuvuin 770 as ...standard was carried out. The oxidation prevention was assessed by the calculation of the main kinetic parameters of thermal degradation process (oxidation induction time and maximum oxidation rate). Supplementary stability tests were performed on i-PP containing four stabiliser couples (triazine+HALS) and the cooperative factors resulting from the synergistic activities of oxidation prevention couple were determined. A kinetic treatment of the chemiluminescence data obtained from thermal ageing of stabilised isotactic polypropylene is presented.
Tests concerning thermal stabilization of various derivatives of 3,5-di-
t-butyl-4-hydroxy ethane and 3,5-di-
t-butyl-4-hydroxy ethene derivatives were performed on isotactic polypropylene or ...low-density polyethylene. Chemiluminescence experiments were carried out in air at 180°C. The kinetic parameters of thermal degradation were calculated from CL data and the efficiency criteria, relative activities and relative stabilities of the thermal oxidation of polymer substrate were evaluated. Synergistic effects of some efficient derivatives and elementary selenium were assessed in i-polypropylene.
Evaluation of oxidation behavior of γ-irradiated EPDM/PP compounds Zaharescu, T.; Jipa, S.; Setnescu, R. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
12/2007, Letnik:
265, Številka:
1
Journal Article
Recenzirano
The oxidation effect of irradiation on ethylene–propylene diene terpolymer/polypropylene blends is presented. The polymer samples consisting of both materials under various ratios (20:80, 40:60, ...60:40 and 80:20) were exposed to γ-irradiation (
137Cs). The irradiation effects were assessed by two methods: oxygen uptake and IR spectroscopy (1720
cm
−1 and 3350
cm
−1, the characteristic bands for carbonyl and hydroxyl groups, respectively). The carbonyl and hydroxyl indexes were calculated for all formulations. From oxygen uptake investigation the kinetic parameters for thermal oxidation of irradiated samples were calculated. The contribution of each component to the progress of degradation is discussed.
The polymer was prepared by γ-ray induced polymerization in air and pyrolysis under argon at various temperatures in the range 600–900°C. The content in the carbon and oxygen increases at the expense ...of decreasing content in nitrogen and hydrogen. The ferromagnetic phase separated from the residue resulted by the pyrolysis of polyacrylonitrile has been analysed using Fourier transform infrared, X-ray diffraction and elemental analysis. The experimental data suggest a layered structure of this polymer with an interlayer spacing of ca 3.5Å and various chemical functions grafted on graphite domains.
In this paper, the grafting of a hindered amine stabilizer (HAS) is studied in isotactic poly(propylene) (PP) films under γ‐irradiation. The HAS used has a definite structure that combines a hindered ...amine functionality and a UV‐absorbing unit (benzylidene malonate ester group) detectable at 308 nm in the UV spectrum of PP film and 314 nm in chloroform. The stabilizer is added to the polymer at various concentration ratios: 0.1, 0.2, and 0.3 wt.‐%. The percentage of HAS grafting in the PP film at various additive concentrations is determined as a function of γ‐radiation dose in the range of 0–100 kGy by direct spectroscopic measurements through the absorption band of the stabilizer in the UV spectra of the PP film. The percentage of free HAS extracted with chloroform from the PP film versus the radiation dose is determined by UV spectroscopy for all the additive concentrations used. This study reveals that only 80% of the HAS is grafted on the 100 kGy irradiated PP matrix independent of the additive concentration used. However, the percentage of HAS grafted on PP films displays an exponential dependence on γ‐radiation dose. These results are consistent with the data obtained on the free HAS content. γ‐Irradiation grafting of HAS in the PP is accompanied by the oxidative degradation of the polymer substrate that is evaluated by increasing the carbonyl index and reducing significantly the oxidation induction time of the PP films.
The percentage of hindered amine stabilizer grafted to the PP film as a function of γ‐radiation dose.
The effect of some 1–4 disubstituted thiosemicarbazide compounds (TSC), including metal complexes, on thermal oxidation of isotactic polypropylene, has been studied, based on the knowledge that TSC ...contain various chemical groups such as CS, –NH– that act as radical scavengers. All compounds exhibit antioxidant properties that represent around half of the effectiveness of Irganox 1076 (a strong phenolic antioxidant) during the induction period and around a quarter of this during the propagation period. The influence of X- atom (as a substituent in the 1st position) decreases in the following order: H
>
Cl
>
Br. R-group (as a substituent in 4th position) seems to exhibit lower influence than X (R
=
cyclohexyl, or phenyl ethyl). TSC complexes with Ni are more effective antioxidants as compared to TSC ligands. The activation energy of oxidation of isotactic polypropylene (i-PP) in the presence of Ni-complexes is very low as compared to the values found in the case of those free of additive i-PP or with other metal complexes. A compensation effect seems to be involved in these cases. A synergistic effect has been observed in the case of Ni(A2)
2–Irganox 1076 couples, while with similar A5 and A6 couples, additive and antagonistic effects were observed, respectively.
