Kinetic study of the thermal degradation behaviour of cellulosic Himalayan nettle fibre

The thermal decomposition behaviour of Himalayan nettle fibre is investigated using dynamic TG analysis under a nitrogen environment at heating rates 5, 10, and 20 °C/min. The pyrolysis of the fibre occurred in three stages. Around 73–75% of the nettle fibre thermally decomposed in the second stage of degradation within the temperature range of 190–450 °C. The average activation energies estimated from the Friedman, FWO, and KAS methods were 173.82, 169.47, and 164.56 kJ/mol, respectively, suggesting the apparent activation energy range of 160–175 kJ/mol, which is suitable for thermoplastic polymer processing. First-order-kinetics can be inferred from the master plot and Coats–Redfern (CR) methods. Eighteen kinetic models were used for the CR method, and among them, three integral functions F1, P2/3 and R3 best-fitted the experimental thermogravimetric data considering the higher correlation coefficient (R² > 0.98). The average activation energy and pre-exponential factors for F1, P2/3, and R3 functions were estimated as 157.24, 154.61, and 135.20 kJ/mol; 5.26E + 12, 5.59E + 11, and 1.86E + 10 min⁻¹, respectively. The master plot method showed the suitability of F1, R3, and P2/3 mechanisms at low temperature and conversion (≤ 0.5), while at higher conversion (0.5–0.8), the dominant mechanisms were R3 and P2/3. The study helps establish Himalayan nettle fibre as a sustainable reinforcement for polymer composite synthesis.