Abstract This study used thermogravimetric analysis to investigate kinetics and synergistic behavior during the co‐pyrolysis of cotton stalk (CS), high‐density polyethylene (HDPE), and their blends, which contained 50% to 90% CS. The experiments were performed under a N 2 atmosphere at heating rates of 5, 10, and 20 °C min −1 over a temperature range of 30–800 °C. The CS thermograms show that it decomposed in three stages, whereas HDPE decomposed in a single step. The blends exhibited three‐stage decomposition similar to CS. Model‐free isoconversional methods, including the Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink methods, were used to estimate the apparent activation energy ( E a ). Pre‐exponential factors were calculated using the Kissinger method for all feedstocks. The average E a values for CS were 163, 166, and 162 kJ mol −1 , and for HDPE were 279, 276, and 277 kJ mol −1 , using the KAS, FWO, and Starink methods, respectively. For the blend containing 10 wt% HDPE, the E a values were close to those of CS. Increasing the HDPE content from 20 to 50 wt% reduced the E a by approximately 9% to 19%. The lowest E a of 132 kJ mol −1 was obtained for the blend containing 50 wt% HDPE across all kinetic models. The co‐pyrolysis experiments demonstrated that a synergistic effect exists between CS and HDPE during co‐pyrolysis, suggesting that these blends have strong potential for the production of value‐added chemicals.
Metta et al. (2026) studied this question.