New paraphenylene diamine antioxidants were prepared. The efficiency and permanence of these oligomer-bound paraphenylene diamines were compared with those of conventional amine-type antioxidants in elastomer blends such as natural rubber/styrene-butadiene rubber and natural rubber/polybutadiene rubber. These oligomerbound antioxidants showed improved aging resistance and ozone resistance in comparison with the blends containing conventional antioxidants. The liquid oligomer-bound paraphenylene diamine could replace the plasticizer required for compounding.

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 xÁy M-SNR, where xÁy 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.

Zinc sulfonated SBR prepared by the sulfonation of styrene units in SBR, followed by the neutralization of the resultant SBR sulfonic acids, behaves as ionic thermoplastic elastomer, and shows improved physical properties compared to SBR. Studies include X-ray fluorescence analyses (XRF), FTIR spectroscopy, dynamic mechanical analyses (DMA) and measurement of physical properties.