Preparation of low molecular weight natural rubber by ozonolysis of high ammonia latex

Kodama S., . and Nishi K., . and Furukawa M., . Preparation of low molecular weight natural rubber by ozonolysis of high ammonia latex. pp. 153-163. ISSN 1511-1768

Depolymerisation of natural rubber (NR) by bubbling ozone into high ammonia latex was attempted in order to prepare liquid natural rubber. NR was found to depolymerise at a faster rate with increasing ozone generation. Addition of hydrogen peroxide to the latex accelerated the depolymerisation of NR. Regardless of added hydrogen peroxide concentration when the pH of latex was above 8 at the initial stage of reaction the rate of depolymerisation was remarkably rapid. However subsequently the reaction abruptly slowed when the pH fell below 8. The decrease in pH was due to the formation of levulinic acid during reaction. These results suggested that the main reaction of the depolymerisation in latex was not direct oxidation by ozone through the formation of ozonide but radical oxidation by hydroxyl and hydroperoxyl radicals formed by reaction between ozone and hydroxyl ion under basic conditions. It seemed that the very slow depolymerisation below pH 8 was due to the formation of levulinic acid from a terminal of a polymer chain by direct oxidation of ozone. The minimum weight-average molecular-weight of the depolymerised NR achieved was about 50000.

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Abstract

Depolymerisation of natural rubber (NR) by bubbling ozone into high ammonia latex was attempted in order to prepare liquid natural rubber. NR was found to depolymerise at a faster rate with increasing ozone generation. Addition of hydrogen peroxide to the latex accelerated the depolymerisation of NR. Regardless of added hydrogen peroxide concentration when the pH of latex was above 8 at the initial stage of reaction the rate of depolymerisation was remarkably rapid. However subsequently the reaction abruptly slowed when the pH fell below 8. The decrease in pH was due to the formation of levulinic acid during reaction. These results suggested that the main reaction of the depolymerisation in latex was not direct oxidation by ozone through the formation of ozonide but radical oxidation by hydroxyl and hydroperoxyl radicals formed by reaction between ozone and hydroxyl ion under basic conditions. It seemed that the very slow depolymerisation below pH 8 was due to the formation of levulinic acid from a terminal of a polymer chain by direct oxidation of ozone. The minimum weight-average molecular-weight of the depolymerised NR achieved was about 50000.

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Item Type:	Article
AGROVOC Term:	Natural rubber
AGROVOC Term:	Depolymerization
AGROVOC Term:	Molecular weight
AGROVOC Term:	Hydrogen peroxide
AGROVOC Term:	Levulinic acid
AGROVOC Term:	Ammonia
AGROVOC Term:	Latex plants
AGROVOC Term:	Liquids
Geographical Term:	Malaysia
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	28 Apr 2025 03:23
URI:	http://webagris.upm.edu.my/id/eprint/23157

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