Nitration of Liquid Natural Rubber by Concentrated Nitric Acid in the Presence of Acetic Anhydride

Khai Minh Doan; Trung Bao Tran; Tuan Duy Nguyen; Vuong Quoc Ly

doi:10.22146/ijc.108473

Nitration of Liquid Natural Rubber by Concentrated Nitric Acid in the Presence of Acetic Anhydride

https://doi.org/10.22146/ijc.108473

Khai Minh Doan^(1*), Trung Bao Tran⁽²⁾, Tuan Duy Nguyen⁽³⁾, Vuong Quoc Ly⁽⁴⁾

(1) Faculty of Special Equipment, Le Quy Don Technical University, 236 Hoang Quoc Viet, Hanoi 100000, Vietnam
(2) Faculty of Special Equipment, Le Quy Don Technical University, 236 Hoang Quoc Viet, Hanoi 100000, Vietnam
(3) Faculty of Special Equipment, Le Quy Don Technical University, 236 Hoang Quoc Viet, Hanoi 100000, Vietnam
(4) Institute of Materials, Biology and Environment, Academy of Military Science and Technology, 17 Hoang Sam, Hanoi 100000, Vietnam
(*) Corresponding Author

Abstract

Liquid natural rubber (LNR) is commonly used as a binder in energetic composites. One of the key areas of interest is the development of energetic polymers to enhance adhesion efficiency and energy. In this study, an energetic liquid polymer—nitrated liquid natural rubber (N-LNR)—was successfully synthesized via nitration of LNR using concentrated nitric acid (HNO₃) in the presence of acetic anhydride (Ac₂O) and dichloromethane as solvent. The effects of key parameters, including the HNO₃/LNR ratio and reaction time, on the degree of nitration and reaction yield were systematically investigated. The degree of nitration was found to increase linearly with the HNO₃/LNR ratio, ranging from 7.97% to 32.9%, with a maximum yield of 76.1%. The optimal reaction conditions were identified as an Ac₂O/HNO₃ molar ratio of 2:1, a reaction time of 1.75 h, and a temperature of 20 °C. Structural analyses by FTIR, ¹H-NMR, and ¹³C-NMR confirmed the presence of cis-1,4-isoprene chains partially substituted with –NO₂ and –ONO₂ groups, verifying successful nitration at the C=C bonds. These results demonstrated a controllable and efficient method for preparing energetic LNR-based polymers with potential application as binders in propellants and plastic explosives.

Keywords

liquid natural rubber; nitration; nitric acid; energetic polymer

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DOI: https://doi.org/10.22146/ijc.108473