Polymer stabilization degradation mechanisms

Thermal stability of nine polymer systems Thermal degradation of blends using TG-DTG-DTA etc Thermal stability, degradation mechanism of organic systems in the presence of inorganic Muhammad 2013... 

It is important to realise that mass spectrometric measurements in TG-MS are not performed directly on the polymer but only evolved gases are detected and identified. Factors influencing component loss from polymeric matrices are volatility, rate of diffusion, solubility in the polymeric matrix, flow-rate, temperature, AT, sample thickness, etc. Therefore, information about the polymeric matrix is obtained in an indirect way, and concerns especially the thermal stability, degradation mechanism and kinetics, performance behaviour, reactivity, and analysis of volatile additives, residuals, monomer occlusions... 

Antony, P., Puskas, J.E., and Kontopoulou, M. The Rheological and Mechanical Properties of Blends Based on Polystyrene-Polyisobutylene-Polystyrene Triblock Copolymer and Polystyrene. Proceedings of MODEST, International Symposium on Polymer Modification, Degradation and Stabilization, Budapest, Hungary, 2002. 

ESR spectroscopy, used in the direct detection or spin trapping modes, is a sensitive method for the detection of polymer fragments and for determining the degradation mechanism. Recent applications for the study of stability in ionomer membranes used as proton exchange membranes in fuel cells demonstrate the capability of ESR to detect details that cannot be obtained by other methods. 

Nitroxyl radicals are formed as intermediates in reactions of polymer stabilization by steri-cally hindered amines as light stabilizers (HALS) [30,34,39,59]. The very important peculiarity of nitroxyl radicals as antioxidants of polymer degradation is their ability to participate in cyclic mechanisms of chain termination. This mechanism involves alternation of reactions involving alkyl and peroxyl radicals with regeneration of nitroxyl radical [60 64],... 

However, the long range effectiveness of polymer additives remains, due to the mechanical degradation, a hitherto unsolved problem. By application of the above-mentioned theoretical approaches and the influence of laminar and elongational flow on polymer stability described in Sect. 6.3.4, it seems possible to retain the flow features over a longer period. It is therefore necessary to reinforce investigations which enable a more quantitative description of turbulent flow, so that in the future structure-property relationships can be established which permit a correlation of the microscopic structure of the macromolecules with the observed flow phenomena. 

TG-FTIR Vulcanisation [32], ageing characterisation [39, 48], sulphur components in rubber [31], polyurethanes [37], polymer degradation mechanisms [30, 40, 41], identification of base polymers [36, 43, 44], thermal stability [46], grafted flame retardants [47], differentiation of EVA rubbers [45] and AN-NBR rubbers [36, 44], degradation of chlorinated natural rubber [42],... 

Furthermore, the effect of hydrated fillers on polymer fire retardancy will depend not only on the nature of the filler, including its particle characteristics (size, shape, and purity) and decomposition behavior, but also on the degradation mechanism of the polymer, together with any filler/ polymer interactions that might occur, influencing thermal stability of the polymer and possible char formation. 

Plastics have to be stabilized to withstand chemical and physical stresses during different phases of their lifetime. Stabilizers protecting plastics against particular degradation processes were developed and commercialized by various companies. According to their principal activity mechanisms, polymer stabilizers are conventionally classified as antioxidants, photoantioxidants, photostabilizers, heat stabilizers and... 

Schwetlick K and Habicher W D (1996) Action mechanism of phosphite and phosphonite stabilizers, In Polymer durability degradation, stabilization and lifetime prediction, Clough R L, Billingham N C and Gillen K T (Eds), Adv Chem Ser 249 349-358. 

Polymer degradation refers to any process that breaks down the molecular structure of macromolecules. The main degradation pathways of concern in oil recovery applications are chemical, mechanical, and biological. The research work on polymer stability from the mid-1970s to late-1980s is summarized in Sorbie (1991). 

Determination of the residual antioxidant content in polymers by HPLC and MAE is one way to determine the amoimt needed for reasonable stabilization of a material, and also to compare different antioxidants and their individual efficiencies. During ageing and oxidation of PE, carboxyhc acids, dicarboxylic acids, alcohols, ketones, aldehydes, n-alkanes and 1-alkenes are formed [86-89]. The carboxyhc acids are formed as a result of various reactions of alkoxy or peroxy radicals [90]. The oxidation of polyolefins is generally monitored by various analytical techniques. GC-MS analysis in combination with a selective extraction method is used to determine degradation products in plastics. ETIR enables the increase in carbonyls on a polymer chain, from carboxylic acids, dicarboxyhc acids, aldehydes, and ketones, to be monitored. It is regarded as one of the most definite spectroscopic methods for the quantification and identification of oxidation in materials, and it is used to quantify the oxidation of polymers [91-95]. Mechanical testing is a way to determine properties such as strength, stiffness and strain at break of polymeric materials. 

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