The influence of polymer type, stabilizers and sample geometry on the relationship between chemiluminescence and oxygen uptake (original) (raw)
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Chemiluminescence as a Probe of Polymer Oxidation
Australian Journal of Chemistry, 2006
Many oxidation reactions of organic materials, including polymers, are accompanied by the emission of weak chemiluminescence (CL). From a study of the mechanism of this weak CL, it is shown that the time development of the CL intensity may provide the kinetics of the oxidation reaction and is thus a sensitive probe of the degradation of the material. The intensity of emission reflects the concentration of peroxidic species in the material. Whereas the kinetics of the oxidation may be described by a series of elementary, homogeneous free radical reactions, the use of imaging techniques has shown that the oxidation of polymers such as polypropylene is highly heterogeneous. A model that describes the oxidation as spreading through the material as an infection from a number of initiating sites is able to rationalize these observations and provide a new approach to the prediction of the useful lifetime of a polymeric material.
Polymer Testing, 2003
An instrument for measuring stress-activated oxidative degradation in polymers is presented. The instrument is based on the chemiluminescence technique using a photo multiplier system to detect photons produced during oxidation or, when measuring in an inert atmosphere, the decomposition of accumulated hydroperoxides. The strain is applied by an Instron tensile testing machine which has been fitted with a light-tight chamber. The temperature and atmosphere surrounding the test specimen are controlled by a small environmental chamber. The oxidation of PA66 during tensile testing has been chosen to demonstrate the instrument.
Chemiluminescence from oxidation of polypropylene: Some comments on a kinetic approach
Journal of Polymer Science Part B: Polymer Physics, 1990
We present a detailed criticism of the kinetic approach to the analysis of data obtained from measurements of the very weak chemiluminescence accompanying the oxidation of polypropylene. It is shown that a kinetic model proposed by other workers is based upon invalid assumptions, leads to kinetic parameters which are not sensible, and requires measurement of the properties which it claims to predict.
Oxidation fronts in polypropylene as studied by imaging chemiluminescence
Polymer Degradation and Stability, 2001
The oxidation of isotactic polypropylene (PP) films containing three different commercial stabilisers has been studied at 150 C in air using imaging chemiluminescence (ICL). The oxidation was initiated using unstabilised PP powder, UV-irradiation or copper. It was shown that the initiated local oxidation spread as a propagating oxidation front in the stabilised PP films. By comparing the speed with which the propagating oxidation front spread, the performance of different stabilisers could be assessed. Furthermore, the influences of temperature, antioxidant concentration and sample thickness on the front speed were compared. The advantage of this technique is a controlled initiation of the oxidation that minimises the influence of weak points in the films. Furthermore, the experimental time is considerably shortened. The position of the oxidation front has been monitored using both ICL and infraredmicroscopy. It was concluded that the technique is effective when evaluating stabiliser performance. Furthermore, it allows the study of oxidation phenomena such as oxidative spreading. The technique was also applied to polyamide 6, however, in this polymer the oxidation did not show the same spreading behaviour. #
An imaging chemiluminescence equipment used for studies of diffusion controlled oxidation effects in pol.vmers is presented. The design involves an imaging photon counting system mounted on a cylindrical oven with a controlled atmosphere. The overshoot on heating is less than 2°C and the temperature during isothetmal conditions is maintained at kO.4"C, thus, a stable thermal environment is attained. To point out possible applications, the monitoring of oxidation profiles from aged nylon specimens and oxygen-barrier properties of an inorganic coating by chemical plasma deposition on a hydroxyl terminated polybutadiene substrate are presented. The results demonstrate the feasibility of studying diffusion controlled oxidation and also the possibility of the technique to estimate the function and durability of su$ace treatments on elastomers. 0 1996 Elsevier Science Ltd.
General characteristics of photoluminescence from dry heat aged polymeric materials
Polymer Degradation and Stability, 2016
Degradation-related polymer luminescence is investigated by means of polarization-sensitive luminescence spectroscopy and anisotropy measurements for different polymers under dry heat ageing conditions. It is found that the spectral development of polymer luminescence with progressive degradation of the polymer is largely independent of the chemical structure and formulation of the polymer. The degradation of the polymer can be categorized into an initial phase with luminescence excited below 300 nm, an intermediate phase with luminescence excited between 300 and 400 nm and a final phase with luminescence excited throughout the full UV/VIS-region. Whereas the properties of the first two phases are consistent with the interpretation as fluorescence originating from individual non-interacting species, the last phase of degradation exhibits luminescence properties, most prominently a high degree of depolarization, consistent with luminescence originating from a density of interacting states that is developed in the process of polymer degradation. A general, polymer independent, model is developed to describe the development of degradation-related polymer luminescence under progressive degradation.
Imaging chemiluminescence instrument for the study of heterogeneous oxidation effects in polymers
Polymer Testing, 1997
An instrument for measuring stress-activated oxidative degradation in polymers is presented. The instrument is based on the chemiluminescence technique using a photo multiplier system to detect photons produced during oxidation or, when measuring in an inert atmosphere, the decomposition of accumulated hydroperoxides. The strain is applied by an Instron tensile testing machine which has been fitted with a light-tight chamber. The temperature and atmosphere surrounding the test specimen are controlled by a small environmental chamber. The oxidation of PA66 during tensile testing has been chosen to demonstrate the instrument.
Thermal oxidation of nonstabilized and stabilized polymers and chemiluminescence
Journal of Polymer Science Part A: Polymer Chemistry, 2004
The chemiluminescence under isothermal and nonisothermal conditions accompanying the oxidation of some polymers (polyolefins, polyamides, and polysaccharides) has been examined from the viewpoint of its relationship with the rate of oxidation. The chemical structure of a given type of polymer plays a decisive role in the resulting shape of the chemiluminescence curves. In the presence of an antioxidant, the inhibition periods of oxidation are shifted to longer times and/or higher temperatures. This shift is directly proportional to the type and concentration of stabilizer. Attention has also been paid to the impact of the average molar mass on the oxidizability of the macromolecular material.
Oxidation of Stressed Polymers as Studied by Chemiluminescence
Ageing Studies and Lifetime Extension of Materials, 2001
Since the use of chemiluminescence (CL) is known to be a very sensitive technique for studying oxidation of polymers, its potential as a tool for studying the oxidation of stressed polymers is thoroughly investigated in this thesis. A number of earlier reports on stress induced chemiluminescence (SCL) show that SCL has potential for elucidating polymer stress reactions. However, the conclusions as to the origin of the light and the effect of stress drawn in these reports are quite ambiguous. The papers summarised in this thesis can be divided into two parts. Papers I, II, II and IV deal with the construction of a specially designed SCL instrument and the origin of the luminescence emitted from some polymers during tensile testing. This luminescence was shown to have different sources reflected in the names: chemiluminescence, thermoluminescence, triboluminescence. It could also be a superposition of two or all three phenomena. The chemiluminescence was shown to originate mainly from hydroperoxide decomposition due to stress-induced adiabatic heating, which after necking is localised in the travelling neck shoulders. This CL was thus not an effect of direct stress. However, some CL was also found to be due to radical formation at fracture, i.e. directly caused by stress. The thermoluminescence proved to be a result of radiation from fluorescent light tubes and was negligible if the specimens were kept in the dark prior to a measurement. The triboluminescence was found to be emitted from irradiated specimens in which stress helped to recombine separated charges. Papers V and VI deal with how sub-yield stresses influence the oxidative degradation of polymers. In order to attain significant oxidation within a reasonable time, the process was accelerated by an elevated temperature. The materials studied were injection moulded parts of polyamide, polypropylene and high density polyethylene. Polyamide was also studied as film, in which there is no restricted oxygen diffusion. It was shown that stress did not change the course of oxidation in any of the materials. In addition to these papers, which all deal with stress chemiluminescence, parts of two papers [VII and VIII], which discuss other specific features of the chemiluminescence technique are also included in the thesis.
Die Angewandte Makromolekulare Chemie, 1998
The imaging photon counting technique was introduced to study polymer oxidation at the beginning of the 90s. The technique, referred to as imaging chemiluminescence (ICL), enables the measurement of both the intensity and the spatial distribution of the weak luminescence from thermo-oxidised polymers. In the short history of ICL measurements the technique has provided data of various aspects of the heterogeneous oxidation of polymers, e.g. diffusion limited oxidation, localisation of stress induced oxidation and the physical spreading of oxidation. The advances in ICL are briefly summarised and recent results obtained by monitoring the oxidation depth profiles in polybutadiene rubber and the physical spreading of oxidation between EPDM particles are presented. The potential and the limitations of the technique are discussed in some detail.