Oxidative Ageing of Polymers

Thermal oxidation ageing effects on silicone rubber sealing performance
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Simulation by reprocessing and thermo-oxidation. Polymer Degradation and Stability 91 e www. Multiple processing and thermo-oxidative ageing clearly alter the oxidative stability and the elongation at break of the materials.

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These changes observed at a macroscopic scale have been related to chemical alterations in the structure of HIPS. The polybutadiene phase was demonstrated to be the initiation point of the degradative processes induced by processing, service life and mechanical recycling. Thermo-oxidative degradation affects more severely the degree of degradation of the material, so it may be deduced that the changes occurring during service life of HIPS are the part of the life cycle that mostly affects its further recycling possibilities and performance in second-market applications.

All rights reserved. Keywords: Recycling; Degree of degradation; High-impact polystyrene; Reprocessing; Thermo-oxidation 1. Introduction of low-molecular weight compounds degradation products, contaminants, etc. In order to investigate the degree of Polymers are subjected to physical and chemical changes degradation of polymeric materials, several approaches can during their processing, service life and further recovery, and be considered, taking into account the changes in their macro- they may also interact with impurities that can alter their com- scopic or microscopic properties.

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The functional group position. These changes substantially modify the stabilization changes by Fourier Transform Infrared FTIR spectroscopy, mechanisms and the mechanical properties of recycled poly- the alterations in the mechanical properties by tensile tests, mers. Therefore, there is a special need to introduce the con- the thermal properties such as the glass transition temperature cept of quality assessment in the recycling activities, in Tg or the degree of crystallinity by differential scanning cal- order to guarantee and specify the properties of the recyclates orimetry DSC are some of the physical, chemical and me- within narrow tolerances by the manufacturers according to chanical analyses which are commonly employed to monitor the needs of their customers [1,2].

According to this, three polymer degradation [4]. Vilaplana et al.

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  • Oxidative Ageing of Polymers.

The sheets were the introduced into a forced-ventila- [6e9]. The samples were removed for ties. The improvement of the impact resistance of analysis after different exposure times of 1, 2, 4, 8, 12 and polystyrene is generally ensured by the polybutadiene intro- 16 days. The polybutadiene nodules are then compatibilised by grafting of 2. Differential scanning calorimetry styrene units [10]. In general, recycled materials show a loss in their properties Differential scanning calorimetry was employed in order to due to the degradation processes that have occurred during assess the oxidative stability of the different samples and the their processing, service life and further mechanical recycling.

A double experimen- aluminium pan, which was sealed and pierced to allow the en- tal approach has been undertaken in order to model the second trance of the flow gas.

The oxidation tempera- processing, while the degradation processes occurring during ture was obtained from the onset point of the oxidation curve the service life was simulated by thermo-oxidative ageing in showed by the calorimetric analysis. Scheme 1 shows the proce- oxidation temperature was performed in triplicate and the av- dure followed for modelling the second life for plastics.

The erage of the three experiments was considered as the represen- samples were characterized by differential scanning calorime- tative value. After reaching this point, the 2. The oxidation induction time was calcu- and thermo-oxidative ageing lated as the difference between the instant when the atmo- sphere was switched to oxygen and the onset of the Virgin high-impact polystyrene HIPS , commercial grade oxidation signal at the DSC thermograms.

The temperature profile in the extruder was lows. The again for further extrusion. Collin GmbH, 2. Melt mass-flow rate MFR Germany.

Atmospheric Oxidation and Antioxidants, Volume II

The virgin HIPS material was subjected to thermo-oxida- The melt mass-flow rate MFR measurements of the re- tive ageing in order to simulate its period of service life. Procedure employed for the modelling of the second life for plastics, a modelling of processing and mechanical recycling; b modelling of service life.

The measurements on each sample were repeated six calorimetry DSC in order to assess the oxidative stability times and the average was taken as the representative value. The oxidation induction time procedure is regulated by inter- 2.

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Tensile properties national standards and is more commonly employed than the oxidation temperature measurements for quality control pur- Tensile tests were performed on reprocessed and aged HIPS poses as a quick screening method to check the activity of samples in order to investigate the changes in the mechanical the stabilization system used [11]. The use of OIT and Tox properties of the material after reprocessing and ageing.

Each methods for the analysis of the oxidative stability of polymeric test was performed according to the procedure established by materials is also evaluated. As it can be from the films obtained by compression moulding. The aver- observed, the stabilising system employed in the material is age value of the modulus, stress at break and elongation at clearly affected by the reprocessing cycles and by thermo-ox- break from the six specimens was set as the representative idative ageing, while the largest changes are observed in the value. In the case of 0. Results and discussion 4 13 8 6 5 13 12 5 3.

Molecular Mobility and Reactivity. Structural Changes Caused by Oxidation. Effects of Oxidation on Physical and Mechanical Properties. Oxidation Under Irradiation. In he created a research laboratory, Laboratoire de Transformation et Vieillissement des polymers LTVP , of which he was the director until at which point he became Professor Emeritus. He has published about papers in scientific journals, mostly on polymer ageing, with others on polymer physics, mainly network properties, and has co-authored about a dozen books and about conferences.

He has obtained 3 scientific awards and 2 honorary medals.