Thesis (M.Sc.)--Chulalongkorn University, 1989

Dry natural rubber (NR) was sulfonated with acetyl sulfate in chloroform at 35"c. The concentration of sulfonic acid groups onto the rubber chain ranged from 0.18 to 0.82 mole7o. After sulfonation the modified NR was neutralized with zinc, lead and magnesium acetate to form an ionic bridge between the polymer chains. The viscosity-average molecular weight (M^) revealed that polymer degradation occurred during sulfonation up to a sulfonic concentration of 0.30 mole7o. After the My leveled off, which would suggest, either that chain scission has ceased and the formation of hydrogen bonding took place, or that a balance between a viscosity increase due to sulfonation and degradation as a result of bond scission. Determination of the water absorption and Wallace Number of the neutralized product indicate a different ion/covalent character between the cations. It was found that Mg + is more ionic than Zn which in turn is more ionic than Pb Due to the susceptibility of NR to degrade during the sulfonation, sulfonated natural rubber ionomers could not be developed. Instead, it obtained a sticky material which has good adhesion properties. ACKNOWLEDGEMENTS The author wishes to express her deepest gratitude to Dr. Jean Fauliimmel and Assistant Professor Suda Kiatkam.iornwong for their generous guidance, understanding, and encouragement throughout the course of this research. The author is grateful to Dr. Krisda Suchiva for allowing her to use the two-roll mill of Mahidol University, and to Dr. Frederick H. Axtell for his advice on polymer testing and sample preparation techniques. Appreciations are also expressed to the Department of Materials Science, Chulalongkorn University and to the Rubber Research Center, Kasetsart University for the use of the Wallace Plastimeter. The author also wishes to thank Assistant Professor Supawan Tanta.yanon, Dr. Amnard Sittattrakul and Associate Profe$sor Boonsong Kongkathip for serving on her committee. Financial assistance from the Graduate school, Chulalongkorn University is gratefully acknowledged.