Stabilization by Increase Termination Rate

Chain breaking antioxidants fall into this second category of stabilizers strategy. They are all able to react with a radicals to give a non-radical species. The most current chain breaking antioxidants are hindered phenols  

Despite it is non-reactive, the R- group influences strongly the physical properties (solubility [33], diffusion [34], evaporation rate [35]...). 

Hindered phenols react by giving a hydrogen atom to a peroxy radical and a phenoxyl radical A°. This one is resonance stabilized. After isomer-izing, it can react following several routes (reaction with another POO°, dismutation or coupling, reaction with oxygen...). Some mechanisms are summarized here below  

Some of those stable products have a negative influence on the aspect properties (yellowing) [36], Some others may have a further stabilizing role [37]. The chemistry of phenols stabilization is actually complex and has hence aroused a considerable amount of literature (see for example [38, 39, 40]). However, we tentatively showed in recent reviews [41, 42] that this mechanistic complexity can well be represented by a kinetically equivalent scheme  

This haves the main advantage of using a limited number of adjustable parameters for simulating the main features of stabilization by phenols in polyolefins (increase of the induction period and minor - or no - changes on the maximal oxidation rate i.e. the steady state characteristics). 

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