Preparation and characterization of thermoplastic polyurethane–urea and carboxylated acrylonitrile butadiene rubber blend nanocomposites

Abstract

This study deals with the preparation and characterization of novel thermoplastic polyurethaneurea (TPUU) and carboxylated acrylonitrile butadiene rubber (XNBR) blends. Blends of different compositions were prepared in tetrahydrofuran using a solution technique, following an ultra-sonication. The chemical reaction between the two inherently immiscible blend phases was determined with the help of Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and 1 H-nuclear magnetic resonance ( 1 H-NMR) spectroscopy. The identification of the new peaks in the FTIR-ATR spectra corroborates the existence of chemical reaction between the carboxylic functional group of XNBR and the amide group of the TPUU. In addition, an increase in the network crosslink density of the blend investigated using 1 H-NMR spectroscopy further supports the occurrence of the chemical reaction between the XNBR and the TPUU. The scanning and transmission electron micrographs of the blend morphology show a uniform dispersion of the minor TPUU phase in the XNBR. Furthermore, the existence of a single glass transition peak also confirms the enhancement in the interfacial miscibility. Additionally, the incorporation of 5 wt % of organomodified montmorillonite nanoclay improves the mechanical properties to a considerable extent in comparison with the unfilled blend elastomeric material.

Carbon nanotubes‐filled thermoplastic polyurethane–urea and carboxylated acrylonitrile butadiene rubber blend nanocomposites

“…Above 0°C, the storage modulus decrease steadily with a transition observed between 44 and 55°C, where it changes abruptly to lower values. This decrease in modulus is mainly due to the melting of a phase, probably the hard segments in the TPUU, which takes place at 44.7°C . However, with increasing the amount of CNTs, this change in the modulus ( E ′) becomes nearly linear, indicating that the CNTs are also distributed in the TPUU phase.…”

“…The preparation and characterization results of the unfilled TPUU:XNBR blends are communicated by the authors elsewhere . It is important to mention that such blend systems have unique mechanical properties due to their good compatibility.…”

“…TEM images of the blend nanocomposite filled with: (a) 3 wt % and (b) 5 wt % of the CNTs. The encircled portions in the images indicate the TPUU phase of the blend system …”

“…From Figure a, it can be observed that the blend sample (TPUU:XNBR) shows slightly higher storage modulus ( E ′) compared to the neat rubber (XNBR). This increase of E ′ can be explained as follows: TPUU urethane/urea–NH group reacts with the carboxylic group of the XNBR phase to form amide linkage, the urethane/urea/amide segments aggregate into microdomains resulting in a structure consisting of glassy, hard domains, and the rest blend phase act as the soft one. The hard domains gain their rigidity through physical crosslinking (hydrogen bonding between them) and provide filler‐like reinforcement to the soft blend phase.…”

“…In the present work, we report for the first time, the preparation and characterization of the MWCNTs (called here after CNTs)‐filled thermoplastic polyurethane–urea (TPUU):carboxylated acrylonitrile butadiene rubber (XNBR) blend nanocomposites. These are very unique blends and have been recently reported by the authors . The mixing of the CNTs was carried out using a laboratory two roll mill.…”