The present investigation deals with the functionalization of acrylonitrile butadiene rubber (NBR) by chemically grafting phosphorylated cardanol prepolymer (PCP) onto its backbone chain. The grafting of PCP onto NBR was accomplished in the latex stage successfully using benzoyl peroxide as the free radical initiator. The functionalized NBR (PCP-g-NBR) is characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. PCP-g-NBR exhibited an increase in molecular weight (4.4%) with an increase in the polydispersity. The grafting parameters have been optimized using "Taguchi L 9 table" and the optimum conditions were found to be "3 phr of initiator concentration, 15 phr of the PCP concentration, reaction temperature of 70 C and reaction time of 6 h." The percentage grafting and grafting efficiency were calculated to be 7.28 and 80.37%, respectively, under optimum processing conditions. The PCP-g-NBR exhibited a reduction in Wallace plasticity number as well as the Mooney viscosity and an enhanced plasticity retention index (PRI) as compared to neat NBR. The rheological measurements exhibited a higher flow behavior index for PCP-g-NBR than the NBR itself. Differential scanning calorimetry and dynamic mechanical analysis results exhibited a decrease in glass transition temperature on functionalization of NBR confirming enhanced plasticization. Thermogravimetric
The present invention deals with the functionalization of acrylonitrile butadiene rubber (NBR) by chemically grafting meta-pentadecenyl phenol (cardanol) onto the backbone chain. This imparts inherent multifunctional characteristics to the nitrile rubber. The grafting of cardanol onto NBR was accomplished successfully in emulsion stage using benzoyl peroxide (BPO) as a free radical initiator. The grafted NBR is characterized by ultraviolet–visible, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Cardanol grafted NBR (CGNBR) shows an increase in molecular weight (6.6%) with an increase in polydispersity index value. The optimal conditions of grafting are found out to be, “1 phr BPO, 15 phr cardanol, at a reaction temperature of 60 °C and a reaction time 10 h” by using the “Taguchi L9 orthogonal array” method. The grafting efficiency and percentage grafting are calculated to be 79.2% and 7.1%, respectively, at the optimum combination of parameters. The CGNBR shows an increase in molecular weight and reduction in Wallace plasticity number as well as Mooney viscosity, but exhibits a higher plasticity retention index value, as compared to ungrafted NBR. The rheological characteristics of CGNBR exhibit a better flow behavior index than NBR. Differential scanning calorimetry, dynamic mechanical analysis results exhibit a decrease in Tg value for grafted NBR. Thermogravimetric analysis results displayed an increase in thermal stability of the functionalized NBR than that of raw NBR.
The physico-mechanical and thermo-mechanical properties of meta-pentadecenyl phenol (cardanol) functionalized acrylonitrile–butadiene rubber (CGNBR) composites containing sodium montmorillonite clay were determined via studies on the functionalization of NBR by grafting cardanol onto its backbone main chain in the latex stage using benzoyl peroxide as a free radical initiator. Results show an improvement in technical properties for functionalized NBR nanocomposites over the NBR nanocomposite. Air and ASTM 3 oil aging studies at 100 °C confirmed an increase in tensile strength and a decrease in elongation at break for CGNBR compared to the dioctyl phthalate plasticized NBR nanocomposite. Fire and flame retardancy studies showed an increased limiting oxygen index for functionalized NBR over the NBR nanoclay composite. Results delineate the method of preparation and characterization of functionalized NBR and oil plasticized NBR nanoclay composites to achieve an improved oil resistance effect for functionalized NBR over NBR nanocomposite.
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