THERMAL OXIDATIVE AGING MECHANISMS IN SINGLE AND TWO PHASE ELASTOMER SYSTEMS-CHARACTERIZATION OF KINETICS AND SPATIAL EVOLUTION

摘要

High lifetime and a long time suitability of rubber products is an important factor concerning sustainability and requirement on modern rubber materials in several applications.A special aspect is the situation using antioxidants like p-phenylenediamines,which are in the focus because of toxicity against aquatic microorganisms and allergic reactions at humans.Of special significance moreover is high thermal oxidative stability,which is important to maintain the physical properties over a long time.To improve this and to predict the material behavior under dynamic or static load,a detailed knowledge about the kinetics and the spatial evolution of the aging process in dependency on temperature,time and sample composition is necessary as well high sophisticated and validated methods.Concerning the spatial evolution of material changes,the diffusion limited oxidation effect(DLO)effect and stability against cracks are important factors.So the investigations are focused on the kinetics,improvement of aging stability and on the DLO-effect in single and two phase elastomer systems,consisting of partially miscible poly-dienes(s-SBR/cis-BR)or completely immiscible NBR/EPDM model systems.The used rubbers have different aging stabilities because of their different molecular structure,which can be used for stabilizing the system.But in this coherence the selected polymers and the morphology of the blend play an important role for the kinetics,and for the consumption or diffusion of oxygen.Beside ATR-FT-IR spectroscopy,low field NMR-spectroscopy and chemiluminescence and an improved micro-indentation method with high resolution is used to characterize the spatial material changes quantitatively,concerning oxidation and crosslink density.The used indentation method allows local dynamic measurement of stiffness especially.Data for lifetime prediction are generated by means of physical properties and tear analyzer measurements in dependency on the aging status(DLO-effect)and used aging parameters(temperature and time).