Document Type : Research Paper

Authors

• Noureddin Nazarnezhad ¹
• Mehran Parastar ²
• Mehran Sinaki ³

¹ Associated Professor, Wood and Cellulose Product Department, Sari Agricultural science and Natural Resources University, Sari, Iran

² PhD student, Sari University of Agricultural Sciences and Natural Resources, Sari, Iran

³ Bachelor's student, Sari University of Agricultural Sciences and Natural Resources, Sari, Iran

Abstract

Background and Objectives: Nitrocellulose, a key cellulose derivative, is widely used in various industries such as explosives, polymeric coatings, photographic films, pharmaceuticals, and biomedical applications due to its high reactivity, solubility in organic solvents, film-forming capability, and controlled combustibility. The applied properties of nitrocellulose are highly dependent on the nature of the cellulose raw material and the nitration conditions. Traditionally, high-purity alpha-cellulose has used as the standard precursor for nitrocellulose production. However, the emergence of cellulose nanofibers (CNF), at nanoscale dimensions, high surface area, and enhanced reactivity, has opened new opportunities for producing modified nitrocellulose with advanced functionalities. Given the fundamental structural differences between alpha-cellulose and nanofibers, investigating how the source material affects the chemical, physical, and thermal properties of nitrocellulose is of significant interest. The aim of this study is to systematically compare nitrocellulose produced from alpha-cellulose and cellulose nanofibers and to evaluate their performance under various nitration conditions.
Materials and Methods: Alpha-cellulose was extracted from wheat straw through acid pre-extraction, soda-anthraquinone pulping, TCF bleaching and final sodium hydroxide (17.5%) extraction. Commercial cellulose nanofibers with diameters of 10–50 nm were used. The nitration process was carried out using a nitric acid–sulfuric acid mixture (3:1 v/v) at 30°C for 45 minutes. Three concentrations of nitric acid (20, 40, and 80 mL) were used to examine the effect of nitration intensity. After the reaction, all samples were thoroughly washed and dried. The resulting nitrocellulose samples were evaluated in terms of degree of substitution (DS), viscosity, degree of polymerization (DP), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and burning rate.
Results: The nitrocellulose derived from alpha-cellulose (NC) exhibited a higher degree of substitution (DS) compared to that obtained from cellulose nanofibers (NNC). In the NC samples, the DS increased from 1.151 at 20 mL nitric acid concentration to 1.454 at 80 mL, while in the NNC samples, the DS values ranged between 1.088 and 1.182. The viscosity of NC decreased from 359.8 cP to 325.9 cP with increasing acid concentration, whereas the viscosity of NNC samples could not be measured due to their plastic-like behavior. The degree of polymerization (DP) of NC decreased from 311 at low acid concentration to 279 at higher concentration. FTIR spectroscopy revealed a reduction in the absorption intensity of O–H bands within the range of 3200–3600 cm⁻¹ and an increase in the intensity of nitro group bands between 1250–1650 cm⁻¹. Thermogravimetric analysis (TGA) indicated higher thermal stability for NNC, as its main decomposition temperature shifted from 200–230 °C in NC to 240–270 °C in NNC. In the burning rate test, NC samples burned faster, with an average rate of 2.8 mm/s compared to 1.9 mm/s for NNC, demonstrating the higher reactivity and flammability of alpha-cellulose-based nitrocellulose.
Conclusion: The type of cellulose precursor plays a critical role in determining the final properties of nitrocellulose. Nitrocellulose prepared from alpha-cellulose, due to its uniform structure and greater accessibility of hydroxyl groups, exhibited higher degrees of substitution and faster burning rates, making it suitable for explosive and coating applications. In contrast, cellulose nanofibers, owing to their nanoscale architecture and larger surface area, produced nitrocellulose with enhanced thermal stability and controlled reactivity, suitable for safer and more advanced uses. These findings can contribute to the optimization of nitrocellulose synthesis and the design of innovative materials for emerging applications in energy, biomedicine, and advanced composites.

Keywords

• Thermal stability
• Degree of substitution
• Surface reactivity
• Burning rate
• Modified cellulose
• Nanostructure

Main Subjects

• Chemical conversion