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ABSTRACT
Materials of significance in the rubber industry generally consist of a complex blend of elastomers, fillers, curing agents and other additives. Elucidating the complex microstructure-to-property relationship of these materials is essential for optimal product development. This requires characterization techniques that are capable to differentiate, map, and quantify these similar materials with sufficiently high spatial resolution. A technique that can provide such chemical microspeciation is Scanning Transmission X-ray Microscopy (STXM). STXM is a beamline based microscopy that utilizes the chemical specificity of Near Edge X-ray Absorption Fine Structure (NEXAFS) combined with zone plate optics to achieve high spatial resolution (< 50 nm) and low beam damage to allow the successful characterization of multi-component materials that would be difficult or impossible with other techniques. A brief introduction to the technique will be presented along with example applications showing curative and filler distribution mapping in multi-component elastomeric systems.
(ProQuest-CSA LLC: ... denotes formulae omitted.)
INTRODUCTION
Elastomer blends are widely used in the rubber industry mainly to enhance product performance with optimal cost. Most of the rubber compound layers present in a tire consist of two or more elastomer components. For the tire innerliner, or the air barrier layer inside a tire, halobutyl (HIIR) rubbers are preferred for their excellent impermeability, durability, cure versatility, compatibility, and co-vulcanizability with other tire rubber components. Among HIIR rubber, bromobutyl (BIIR) is most widely used. BIIR have somewhat higher Tg than those of natural rubber (NR), butadiene rubber (BR), and isoprene rubber (IR). Commonly, NR is blended in with HIIR in an innerliner compound at 10 to 30 phr for improved low temperature performance, green strength, and cure adhesion. NR, instead of BR, is used for its better compatibility with isobutylene-based elastomers, such as HIIR.1
The most pertinent properties pertaining to elastomer blends in rubber compounds are homogeneity of mixing (phase morphology), cure compatibility, and curative and filler phase distribution and migration. The relative compatibility between NR and BIIR ensures the fine dispersion phase morphology of NR in BIIR in a BIIR/NR innerliner compound, typically with an average dispersion size less than 0.5 ìç. Fillers, such as carbon black (CB) and silica, were found to be preferentially partition into BIIR, although they tend to be crowded at the interface.2 Curative...