In this study, we investigated a network of carboxylated nitrile rubber crosslinked by biologically derived coordination complexes that possesses good room temperature self-healing properties in addition to high tensile strength, stretchability, and recyclability. First, we showed the synthesis and analysis of coordination complexes composed of two metal salts (nickel nitrate and zinc nitrate), whose corresponding thiol and amino groups engage with the L-cysteine amino acid to produce the complex. Infrared spectrum, X-ray pattern, mass spectroscopy, energy-dispersive X-ray analyses (EDX), and morphology (SEM and TEM) analysis have all been used to characterize the metal−cysteine complexes. These Ni−cysteine and Zn−cysteine complexes have an apparent behavior after addition to XNBR rubber, as observed by several investigations (including swelling experiment, rubber process analysis, universal testing machine (UTM) analysis, and morphological analysis). Therefore, compared to the Ni-cysteine-and pristine cysteine-cured XNBR compounds, the Zn−cysteine complex-cured XNBR compound showed extreme stretchability, recyclability, and strong tensile strength of 3.8 ± 0.2 MPa. It also had a remarkable healing performance of 89.5%. This concept is strongly approved by the increased physico-mechanical properties of XNBR rubber and the recyclability with self-healing capability.
This study investigates (ZnO)s with different surface features as vulcanization activators in unfilled SBR vulcanizates. ZnO is termed the best activator due to its fast reaction kinetics. A high release of ZnO into the environment harms marine ecosystems, and most ZnO production goes to the rubber sector; therefore, reducing ZnO amount is essential. Active, nano and functionalized ZnO compared to conventional ZnO in SBR matrix; concentration optimized based on curing, mechanical, physical, and dispersion analyses. The Arrhenius equation approximated the cure curve's kinetic constant and activation energy. Crosslink density measured by swelling experiment and solvent freezing point depression. Nano ZnO was used from 0.5 to 2phr, active ZnO from 1 to 4phr, and functionalized ZnO from 1 to 3phr compared to 5phr of conventional ZnO. The tensile strength of N1.5, F1.5, and A2 SBR increased by 5%, 26%, and 18% compared to C5SBR, whose elongation at break improved by 30%, 7%, and 23%. The data were analyzed using tukey HSD post hoc test. Regarding mechanical properties and curing characteristics, 2phr active, functionalized, and 1.5phr nano ZnO is analogous to 5phr conventional ZnO in an unfilled SBR matrix. The quantity of ZnO in rubber vulcanizates decreased successively by 60%, 60%, and 70%.
To the best of our knowledge, for the first time, metal-organic framework (MOF), a porous reticular structure, has been tried as a reinforcing filler for rubber. A MOF synthesized by solvothermal reaction between 2-aminoterephthalic acid and aluminum chloride hexahydrate was characterized and incorporated as reinforcing filler in SBR. A comparative investigation on the properties of the well-dispersed, thermally stable nano-MOF composite (SBR-MOF) was carried out with reference to SBR–nano alumina composite (SBR-nAl). The SBR-MOF was mechanically more robust than SBR-nAl. The SBR-MOF showed 130% improvement in tensile strength over the pristine SBR composite and 50% better elongation at break than SBR-nAl at 10 phr loading. The thermal and dynamic mechanical properties of SBR-MOF are superior to SBR-nAl composite. The highly porous organic framework was favorable for the enhanced entanglement of polymer chains at the interface. The effectiveness of the organic framework on the dispersion and compatibility was evaluated by scanning electron microscopy. The dispersion studies substantially supported the overall property enhancement. To substantiate the superiority of MOF in the rubber matrix, the tensile properties of SBR-MOF were compared with SBR composites filled with nano silica, nano titania, as well as nano silica and nano alumina with a compatibilizer, thereby documenting a promising nanofiller for introduction into the rubber industry.
An important factor for the preparation of thermoplastic vulcanizates (TPVs) is the mixing sequence or technique as it is controlling the product quality and production rate. The effect of different routes of mixing sequences on the mechanical properties and rheological properties have been studied. Four different types of mixing sequences have been pursued and ultra-high molecular weight EPDM (UHMW-EPDM) master batch technique has shown maximum prospect over the melt blending method. Co-agent master-batch sample showed optimum balance between TS and %EB over the other master-batch samples. Melt blending technique shows moderate properties for all cases. Rheological data follows the same trend as observed for the mechanical properties. Crosslink density also found the highest for the co-agent master-batch sample and co-agent/peroxide master-batch sample over the other two samples. Cryo-fractured and etched TPV samples were prepared and examined in FE-SEM. Co-agent master-batch sample shows the droplet type morphology.This new type of UHMW-EPDM based TPV with co-agent/rubber masterbatch mixing technique leads to superior physico-mechanical properties over the other mixing techniques. These newly established TPVs can be used as various injection molded parts, esthetic seals/strips and 2K-molds for the automotive applications.
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