Nanocomposites composed of chlorinated ethylene propylene diene monomer rubber (Cl‐EPDM) with various contents of hydroxyapatite nanoparticles (HA) were prepared in an open two‐roll mixing mill. The effect of nanoparticle concentration on structural, morphological, thermal, and electrical properties were examined by different characterization technique such as Fourier transform infrared spectroscopy (FTIR), UV, X‐ray diffraction (XRD), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), thermogravimetric analysis (TGA), and impedance analyzer. The shift in the IR and UV absorption frequencies of nanohybrid relative to that of chlorinated EPDM indicated the successful encapsulation of crystalline hydroxyapatite particles in the modified elastomer chain. The X‐ray diffraction pattern of the fabricated composite revealed the more ordered arrangement of nanoparticles within the elastomer chains and the amorphous nature of polymer decreases with raise in filler loading. The examination of nanocomposite morphology by SEM showed that the inorganic particles were well dispersed in the organic phases. TGA analysis showed the enhanced thermal stability of the composites with increase in the loading of nanoparticles. Shift in the glass transition temperature to a higher value in DSC thermograms of new hybrid indicated the increased orderness of the Cl‐EPDM/HA nanocomposite. The AC electrical conductivity was influenced significantly by the frequency of applied field and the concentration of nanofiller. Dielectric properties strongly distort at lower frequencies but became independent as frequency increased above 103 Hz. POLYM. COMPOS., 39:2093–2100, 2018. © 2016 Society of Plastics Engineers

Hydroxyapatite nanoparticles (HA) reinforced polymer blend based on chlorinated nitrile rubber (Cl‐NBR) and chlorinated ethylene propylene diene monomer rubber (Cl‐EPDM) were prepared. Resulting blend composites were analyzed with regard to their rheometric processing, crystallinity, glass transition temperature (Tg), mechanical properties, oil resistance, AC conductivity, and transport behavior. The decrease in optimum cure time with the addition of HA is more advantageous for the development of products from these blend nanocomposites. The XRD, FTIR, and SEM confirmed the attachment and uniform dispersion of HA nanoparticles in the Cl‐NBR/Cl‐EPDM blend. The good compatibility between polymer blend and nanoparticles was also deduced by the formation of spherically shaped HA particles in the blend matrix determined by TEM analysis. DSC analysis showed an increase in Tg of the blend with the filler loading. The addition of HA particles to the blend produced a remarkable increase in tensile and tear strength, hardness, AC conductivity, abrasion, and oil resistance. The diffusion of blend composites was decreased with an increase in penetrant size. The diffusion mechanism was found to follow an anomalous trend. Among the blend composites, the sample with 7 phr of HA not only showed good oil and solvent resistance but also a remarkable increase in AC conductivity and mechanical properties.

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Novel chlorinated acrylonitrile butadiene rubber (Cl-NBR) was prepared from NBR by the alkaline hydrolysis of chloroform by using phase-transfer catalysis. The formation of Cl-NBR was monitored by 1 H-NMR, UV-Vis, and Fourier transform infrared spectroscopic techniques. The percentage of chlorine attached to the rubber chain was estimated by Volhard method. The effect of polar groups on the structural and thermal properties of Cl-NBR was analyzed by scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, and thermogravimetric analysis studies. The flame retardant, oil resistance, cure behavior, and mechanical properties of chlorinated elastomer were also analyzed. The proton NMR revealed the attachment of chlorine in the backbone of NBR with new chemical shift values. The C-Cl stretching of chlorinated NBR was confirmed from Fourier transform infrared. The UV spectrum also supported the formation of chlorinated unit in the NBR chain through the shifts and broadening of absorption peaks. The X-ray diffraction analysis pattern indicated a decrease in the amorphous domain of NBR with an increase in the level of chemical modification. The increased glass transition temperature obtained from differential scanning calorimetry confirms the increased molecular rigidity of the chlorinated NBR and thermal transitions increased with increase in the level of chemical modification. The thermal stability of Cl-NBR decreased with an increase in chlorine content. The flame and oil resistance of Cl-NBR was greatly higher than pure NBR due to the increased polarity of modified rubber. The superior tensile strength of Cl-NBR (4 times higher than pure NBR) and higher oil resistance find applications in pump diaphragms, aircraft hoses, oil-lined tubing, and gaskets materials with the excellent flame resistant property.