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Author: S. V. Peddada Publisher: ISBN: Category : Languages : en Pages : 43
Book Description
The mechanism of degradation of poly(bis(trifluoroethoxy)(phosphazene) (PBFP) and poly(bis(phenoxy)(phosphazene) (PBPP) have been examined using dynamic and isothermal thermogravimetry. The dynamic experiments were made between 50 deg and 750 deg C at several heating rates from 2.5 deg to 80 deg C/min. and the isothermal measurements were made at 325 deg, 340 deg, 355 deg and 370 deg C. The polymers and their degraded residues were characterized by gel permeation chromatography, infrared spectroscopy and intrinsic viscosity. In PBFP, the overall activation energy for degradation (Ed) was between 23.2 (isothermal) to 26.6 (dynamic) kcal/mole. The order of reaction was 0.3 + or - 0.1. Maxima in the rates of isothermal degradation occurred between 30 and 35% weight loss. Based upon experimental results, the mode of initiation in PBFB was deduced as occurring at the chain ends. Sample molecular weight dropped rapidly with degradation in harmony with a few random breaks occurring at weak points along the main chain after the degradation has been initiated at the chain ends. Literature results on the thermal degradation of PBFP in vacuum was shown to be consistent with a terminal initiation-chain transfer mechanism.
Author: S. V. Peddada Publisher: ISBN: Category : Languages : en Pages : 43
Book Description
The mechanism of degradation of poly(bis(trifluoroethoxy)(phosphazene) (PBFP) and poly(bis(phenoxy)(phosphazene) (PBPP) have been examined using dynamic and isothermal thermogravimetry. The dynamic experiments were made between 50 deg and 750 deg C at several heating rates from 2.5 deg to 80 deg C/min. and the isothermal measurements were made at 325 deg, 340 deg, 355 deg and 370 deg C. The polymers and their degraded residues were characterized by gel permeation chromatography, infrared spectroscopy and intrinsic viscosity. In PBFP, the overall activation energy for degradation (Ed) was between 23.2 (isothermal) to 26.6 (dynamic) kcal/mole. The order of reaction was 0.3 + or - 0.1. Maxima in the rates of isothermal degradation occurred between 30 and 35% weight loss. Based upon experimental results, the mode of initiation in PBFB was deduced as occurring at the chain ends. Sample molecular weight dropped rapidly with degradation in harmony with a few random breaks occurring at weak points along the main chain after the degradation has been initiated at the chain ends. Literature results on the thermal degradation of PBFP in vacuum was shown to be consistent with a terminal initiation-chain transfer mechanism.
Author: N. Grassie Publisher: Springer Science & Business Media ISBN: 9400934254 Category : Science Languages : en Pages : 282
Book Description
The purpose of this volume, like that of its predecessors in the series, is to present a selection of topics which are representative of the continually expanding area of polymer degradation. It will be obvious that some of these topics emanate from academic studies, others from more applied backgrounds, but it is anticipated that all will be seen to be of vital relevance to one or other of the currently advancing fields of polymer technology. The first two chapters deal with specific classes of polymers, and particularly with their mechanisms and products of thermal degrada tion. Thus in Chapter 1 Dr McNeill discusses the reactions of the ammonium, alkali and alkaline earth metal salts of poly(methacrylic acid) and their copolymers with methyl methacrylate. These water soluble 'ionomers' have valuable technological applications. In Chap ter 2 Professor Montaudo and Dr Puglisi perform a valuable service by drawing together and critically reviewing, for the first time to my knowledge, the mechanisms of thermal degradation of the various classes of condensation polymers which are of industrial significance. This includes, for example, the polyurethanes, polyureas, polyesters, polycarbonates, polyamides, polyimides, polyethers, polysulphides, polysulphones, polyschiff bases, polysiloxanes and polyphosphazenes.
Author: Krzysztof Pielichowski Publisher: Elsevier ISBN: 0128231424 Category : Technology & Engineering Languages : en Pages : 379
Book Description
Thermal Degradation of Polymeric Materials, Second Edition offers a wealth of information for polymer researchers and processors who require a thorough understanding of the implications of thermal degradation on materials and product performance. Sections cover thermal degradation mechanisms and kinetics, as well as various techniques, such as thermogravimetry in combination with mass spectroscopy and infrared spectrometry to investigate thermal decomposition routes. Other chapters focus on polymers and copolymers, including polyolefins, styrene polymers, polyvinyl chloride, polyamides, polyurethanes, polyesters, polyacrylates, natural polymers, inorganic polymers, high temperature-resistant and conducting polymers, blends, organic-inorganic hybrid materials, nanocomposites, and biocomposites. Finally, other key considerations such as recycling of polymers by thermal degradation, thermal degradation during processing, and modelling, are discussed in detail. Explains mechanisms of polymer degradation, making it possible to understand and predict material behavior at elevated temperatures Offers systematic coverage of each polymer group that is supported by data detailed explanations and critical analysis Investigates thermal decomposition routes in new materials, such as organic-inorganic hybrid materials and polymer nanocomposites
Author: J. H. Magill Publisher: ISBN: Category : Languages : en Pages : 11
Book Description
Polyphosphazenes were first synthesised towards the end of the last century. Now, a wide variety of polymers and copolymers with alkoxy, aryloxy and aminoxy groups have been synthesised. Recently, side chains have been connected directly to the backbone phosphorus modifying physical properties considerably. Variations in side group chemistry enables a wide span in properties to be covered ranging from glass temperatures approaching -100 C to melting points well above 300 C in some systems. Thermotropic behavior persists over a range of temperature. It was determined that degradation mechanisms were also important in determining thermal stability. For example, alkoxy phosphazenes degraded primarily via a chain unzipping process leaving little or no residue, whereas aryloxyphosphazenes mostly disintegrated through random chain scission (involving some chain transfer too) leaving a substantial residue.
Author: E. Grant Jones Publisher: ISBN: Category : Languages : en Pages : 127
Book Description
The results of a TGMS analysis of a series of polymers are presented. Sample weight loss and volatile gas evolution during programmed heating of polymers are correlated in order to investigate thermal stability and the mechanism of thermal degradation. Thermal polymerization at 434 K of bis(4-(3- ethynylphenoxy)phenyl)sulfone (I) in the initial stages of reaction and of 4-(3- ethynylphenoxy)phenyl phenyl sulfone (II) up to 90% conversion was found to yield polymers with number-average molecular weights approaching 3000.
Author: S. V. Peddada
Author: S. V. Peddada
Author: 
Author: N. Grassie
Author: 
Author: J. D. Ingham
Author: Krzysztof Pielichowski
Author: J. D. Ingham
Author: Samuel Leo Madorsky
Author: J. H. Magill
Author: E. Grant Jones