Mechanisms of chemical ageing introduction

This part of the chapter will be divided into four main sections. This first section will be devoted to common aspects of chemical ageing processes. The second section will be devoted to reaction-diffusion coupling, and the last two will focus on hydrolytic and oxidative ageing respectively. Durability problems will be considered essentially from the material science point of view rather than the chemical mechanism point of view. Emphasis will be put on the consequences of chemical ageing on mechanical properties. 

Structural scale Entity Main analytical tools Theoretical tools 

Morphological Crystalline lamellae Spherulite SAXS, WAXS, DSC SEM, TEM, AFM Materials science 

Macroscopic Skin-core structure Visible microscopy Modulus profiling Nano- and macroindentation Materials science 

Hydrolysis without chain scission occurs only in acrylic and vinylic polymers with ester side groups. These polymers are not frequently used as composite matrices. Oxidation leads to a predominating chain scission process in the majority of cases, and to a predominating cross-linking in few cases such as polybutadiene (Coquillat et al., 2007). An important quantity is the yield of chain scission or cross-linking expressed as the number of broken chains or cross-links formed per oxygen molecule absorbed. There is, to our knowledge, no case of industrial polymer for which this quantity is null. 

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