Novel Blends of Nitrile Butadiene Rubber and in-Situ Synthesized Thermoplastic Polyurethane-Urea: Preparation Method, Characterization and Properties

The blending of conventional elastomeric materials is an energy and cost effective route to obtain new materials with a useful combination of performance characteristics not available in individual elastomers. To follow this theme, the reactive-blending of thermoplastic polyurethane-urea (PUU) with nitrile butadiene rubber (NBR), in contrast to the conventional melt-and solvent blending methods, is realized in the present work. The PUU was synthesized in-situ from its precursors during blending with NBR in an internal mixer to obtain a new kind of NBR/PUU blends. The structural characterizations of prepared blends by ¹H NMR spectroscopy confirmed the in-situ synthesis of PUU during the reactive-blending process. Importantly, the ¹H NMR spectroscopic analysis shows up to 90% conversion of the precursor (chain extender) to an in-situ synthesized PUU. Blends up to 70/30 (NBR/PUU) weight ratio were prepared, structurally characterized and compounded with curatives on a two-roll mixing mill in order to vulcanize the rubber phase. The blend vulcanizates showed a remarkable improvement in stress-strain behavior, hardness, tear strength, abrasion loss and dynamic-mechanical behavior. Further structural and morphological characterization of the blend vulcanizates was followed by differential scanning calorimetric analysis, x-ray diffraction and transmission electron microscopy. Such blends can find cost-effective utilization in areas requiring high mechanical and dynamic-mechanical performance characteristics like rubber rollers, industrial wheels, belting, pump impellers etc.