Struktur und Eigenschaften temperatur- und ölbeständiger Elastomere: Einfluss von Weichmachern, Vernetzern und verstärkenden Füllstoffen

Abstract

The impact of softeners (DOP, DBP) on the rheological response of HNBR melts is discussed in the frame of compatibility and wall slip effects based on entropic segregation. The influence of filler flocculation of carbon black on oscillatory and steady shear flow properties is described and analyzed by dielectric spectroscopy measured online in a plate-plate rheometer for nitrile butadiene polymer (NBR) and its hydrogenated analogue (HNBR). Further investigation on the properties of fluor elastomers, which contain modifications of carbon black via ionic liquid, are described and analyzed regarding the compatibility of filler and polymer. Combined mechanical and NMR experiments were performed on bulk as well as swollen elastomers to charactarize polymer chain dynamics. Uniaxial stress-strain experiments in combination with current models of entangled rubber elasticity were used to disentangle the contributions from entanglements and chemical cross-links (including trapped entanglements) in a series of peroxide-cross-linked nitrile butadiene rubber (NBR) and its hydrogenated analogue (HNBR). The role of network defects was assessed by ultra slow stress-strain experiments and dynamic mechanical analysis. These macroscopic properties were compared with molecularscale information obtained by advanced proton NMR spectroscopy techniques applied to bulk and swollen samples, which provide information on average cross-link density, its spatial heterogeneity, entanglement contributions, and the amount of inelastic defects. In addition to the typical heuristic horizontal shift based WLF equation, investigation on the thermal expansion coefficient measured via optical diffraction method has been implemented into an approach to determine vertical shift of pure nitrile butadiene polymer (NBR) and its hydrogenated analogue (HNBR) both with 39 % ACN content.