Polymer degradation chemical aspects

A systematic study of both physical and chemical aspects in plastics pyrolysis was launched in the Cycleplast project [6]. Thermal degradation of commodity polymers, including kinetic factors and mechanism, were systematically investigated by Professor Bockhom and collaborators, using thermogravimetry, linked with mass spectrometry, as well as closed loop laboratory-scale pyrolysis reactors. The resulting kinetic parameters are discussed further. 

Borup R, Meyers J, Pivovar B, Kim Y S, Mukundan R, Garland N, Myers D,Wilson M, Garzon F, Wood D, Zelenay P, More K, Ken Stroh K, ZawodzinskiT, Boncella J, McGrath J E, Inaba M, Miyatake K, Hori M, Ota K, Ogumi Z, Seize Miyata S, Nishikata A, Siroma Z U, Chimoto Y, Yasuda K, Kimijlma K and Iwashita N (2007), Scientifle aspects of polymer electrolyte fuel cell durability and degradation, Chemical Reviews, 107,3904-3951. 

Bomp, R., et al. 2007. Scientific aspects of polymer electrolyte fuel cell durability and degradation. Chemical reviews 107 (10) 3904-3951. 

Bomp R, Meyers J P, Pivovar B, Kim Y S, Mukundan R et al. (2007), Scientific Aspects of Polymer Electrolyte Fuel Cell Durabihty and Degradation , Chemical Reviews, 107, 3904-3951. 

Because of the more practical aspect of polymer stability in the numerous proposed uses of intrinsically conducting polymers, including polyaniline and its relatives, and the more fimdamental interest in the chemistry of processes that change the chemical identity and various solid state properties of the polymers, degradation studies are warranted. These studies focussed initially on the mere rate of degradation (which may be of very practical interest). Wth purely electrochemical measiuements, Kobayashi et al. [512,513] showed that the two peaks in qrclic voltammograms of PANI di-... 

Gugumus, F. Re-examination of the role of hydroperoxides in polyethylene and polypropylene chemical and physical aspects of hydroperoxides in polyethylene. Polymer Degradation and Stability, 49 (1995), p. 29 - 50... 

Allen, N. S. Thermal and photo-chemical oxidation of Nylon 6,6 Some aspects of the importance of a, p-unsaturated carhonyl groups and hydroperoxides, Polymer Degradation and Stability, 8 (1984), p. 55-62... 

A good understanding of the physical and chemical aspects of degradative processes and of the decomposition of polymers facilitated the development of important practical applications, such as ... 

It should be noted that MWD is not a permanent characteristic of the polymer, as the macromolecules are prone to degradation. There are several kinds of degradation thermal, mechanical, chemical, radiative, and biological. In polymer hydrodynamics, the aspect of prime importance is the rupture of the polymer chains when the polymeric melt is subjected to high shear rates. This changes the MWD of the polymer. This reduction in chain length often reduces the utility of the polymer for a particular application. 

Antioxidants and stabilizers were used on a trial-and-error basis more than 100 years ago. Real scientific and technological progress is relatively recent. It was ushered in by the development of a basic understanding of the underlying mechanisms of polymer degradation. This has made it possible to ascribe specific chemical and physical functions to antioxidants and stabilizers according to their mode of action in the oxidative process. An important aspect in the development of antioxidants is that their effectiveness does not only depend on the chemical inhibition process but also on physical factors such as solubility of antioxidants and their compatibility with the polymer, diffusion and migration phenomena within the polymer matrix, volatility and extractability of antioxidants. Some historical perspectives of this development has been reviewed recently. ... 

Several review articles are available on the synthesis, physico-chemical properties, and bio degradability of natural-based polymers, and their composites [6-9]. The same aspects have been the subjects of recent books [10-12]. In the following account, we concentrate on organic esters of cellulose. 

Last but not least, DSC is a powerful technique for many other polymer-relevant aspects such as monitoring of curing reactions, detection of degradation, determination of heat capacity of chemical conversions, monitoring of initiator decomposition, etc. 

Thus, there are three possible pathways for the radiation degradation of polymer molecules neutral radical, cation-radical and/or anion-radical intermediates. Interest in the formation of these three types of reaction intermediates has fluctuated over the years with the utilization of different techniques and with the particular interests of different investigators. It is likely that all three species will be produced, but their relative importance in the degradation mechanism will depend on the chemical structure of the polymer. Evidence for their involvement will depend on the experimental methods used and the temperature and time scale of observation. In this paper we illustrate our investigations of many of the fundamental aspects of the radiation degradation of polymers through studies of series of polymers and copolymers. 

---