Heterogeneous polymer degradation

Physical Techniques for Profiling Heterogeneous Polymer Degradation... 

G. George and M. Celina, Homogeneous and heterogeneous oxidation of polypropylene. In S. Halim Hamid and M. Dekker (Eds.), Handbook of Polymer Degradation, Second Ed., Inc., M. Dekker, New York, p. 277. 

A useful reference for the study of polymer heterogeneity by ESR spectroscopy is [78]. The reader is also referred to the Chapter 12 by Schlick and Kruczala in this book, which covers ESR and polymer degradation, including imaging methods. 

Specific enzymatic degradation has been useful in determining the structures of pectins, gums and other plant polysaccharides (115), the mucopolysaccharides of higher animals (116), and other complex carbohydrates (117) including those from microorganisms 118, 119, 120). In these heterogeneous polymers enzyme treatment is most useful for deter-... 

M. Celina and G.A. George, Heterogeneous and homogeneous kinetic analysis of the thermal oxidation of polypropylene, Polym. Degrad. Stab. 1995, 50, 89-99. 

Diffusion-controlled monolithic system The active ingredient is released by diffusion prior to or concurrent with the degradation of the polymer matrix. Rate of release also depend upon where the polymer degrades by homogeneous or heterogeneous mechanism. 

The knowledge of conditions under which polymers degrade is essential to avoid and retard corrosion. Chemical properties of macromolecules are essentially those of small molecules only the reactivity is lower and the reaction conditions may be different. For example, polymer degradation caused by corrosive chemicals occurs in heterogeneous systems, since chemicals have to diffuse inside polymer matrices and the rate of diffusion of adverse chemicals depends on the chemical structure of polymers and on conditions such as temperature, humidity, etc. 

EPR is used extensively to detect, identify and follow the fate of radicals involved in polymerization or polymer degradation processes. It is also used extensively to characterize polymeric materials in terms of their morphology, heterogeneity, structural transformations, chain dynamics, and so on [2-5]. For this purpose, one can take advantage of the stable paramagnetic centers present in material to be examined (e.g., residual post-polymerization radicals, or TMIs used as catalytic centers or stabilizers). In most cases, however, external spin probes are added, including spin-labeled macromolecules (see Sections 23.2.1.5 and 23.2.2.1) [6]. The sensitivity and high content of structural information contained in the spin Hamiltonian parameters allow to obtain valuable - and often unique - data on the studied systems [7]. 

Goss, B.G. S., Nakatani, H. et al. Catalyst residue effects on the heterogeneous oxidation of polypropylene. Polymer Degradation and Stability, 82 (2003), p. 119-126... 

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