Iran Polymer Institute, P.O. Box 14965-115, Tehran, I.R. IRAN
The effects of solvent, temperature, time, weight percent of catalyst on the rate and mechanism of cyclization of natural rubber (NR) was studied in toluene and xylene solutions having tin tetra chloride catalyst (SnCl4). Iodometric titration show, with 8% SnCl4 (based on polymer weight) cyclization occurs, leaving 27.4% of the total unsaturation. Infrared spectra of cyclized NR show decreased absorption intensity at 840 and 780 cm-1 which are characteristic bands of the linear polymer and the appearance of absorption and at 890 cm-1 as cycles were formed. By using this chemical modification, NR is transformed into a resinous thermoplastic, hard, non rubbery cyclized material with much less unsaturation than the original rubber, which ou7ld find commercial applications as adhesives, printing inks, industrial and ship paints.