Abstract
Zinc sulfonated natural rubbers having different sulfonate contents were synthesized by the reaction of natural rubber with acetyl sulfate, followed by the neutralization of the resultant polymeric sulfonic acid with zinc acetate. The sample notation used for the ionomer is x y M-SNR, where x y is the degree of sulfonation expressed as meq/100 gm rubber, M is the neutralizing metal ion and SNR shows sulfonated natural rubber [Weiss, R.A., Fitzgerald, J.J. and Kim, D. (1991). Macromolecules, 1064: 24]. The modified samples of natural rubber were characterized using spectroscopic techniques such as X-ray Fluorescence Spectroscopy (XRFS), Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICPAES), Fourier Transform Infrared Spectroscopy (FTIR), Fourier Transform Nuclear Magnetic Resonance Spectroscopy (FTNMR), and by the evaluation of mechanical properties. The results show that the incorporation of sulfonate groups into NR improved its physical properties drastically. At a sulfonate level of 24.6 meq/100 g rubber, the tensile strength of the modified rubber incredibly increased to 13 MPa compared to the tensile strength of 0.36 MPa shown by unvulcanized base natural rubber. The Zn-SNR thus synthesized could be reprocessed at 150 C without sacrificing much of its tensile strength.
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