Properties and rheological behaviour of cellulose nanocrystal (CNC) in thermoplastic polyurethane / Afkar Rabbani Hidayatullah Bin Hipeni

Faculty of Chemical and Process Engineering Technology

Thesis (Master of Science) -- Universiti Malaysia Pahang - 2025

Includes bibliographical references

Extraction of Cellulose Nanocrystals (CNC) from its mother cell which is cellulose is commonly conducted by the utilization of acid hydrolysis process. Conventionally, CNC is produced using acids such as sulphuric and phosphoric acid. However, extraction of CNC via acid hydrolysis process requires large volume of solvents, having low thermal stability and is deemed infeasible to be scaled up in the industrial level. Most recently, CNC was extracted with the combination of acids which is in this case phosphoric and hydrochloric acid in acid hydrolysis in the effort to reduce the usage of solvents for CNC extraction process. CNC then were used as reinforcing agents in Thermoplastic Polyurethane (TPU) as the base polymer matrix and melt compounding process is selected for the fabrication of CNC/TPU nanocomposites film. Nevertheless, research on the rheological behavior of CNC/TPU nanocomposites is still limited, and work on mixed-acid CNC/TPU nanocomposites has yet to be reported. Therefore, the overall purpose of this study is to extract CNC with an improved process in the context of solvent usage reduction and also to study the rheological behavior of mixed acids CNC/TPU nanocomposites. CNC were extracted from Microcrystalline Cellulose (MCC) as the source of cellulose. In this study, sulphuric, phosphoric, and hydrochloric acids were used individually in the acid hydrolysis process to extract CNC, while a mixture of phosphoric and hydrochloric acids was employed to obtain mixed-acid CNC. CNC/TPU nanocomposites were fabricated by the melt compounding process which can be divided by two major processes which is extrusion and followed by heat press molding process. CNC was characterized by using Transmission Electron Microscopy (TEM) to study its morphology and was supported by Thermogravimetric Analysis (TGA) for the thermal stability of CNC. CNC/TPU nanocomposites were characterized in terms of mechanical properties, spectroscopic characterization and physical appearance in order to support the main findings obtained in the rheological properties of CNC/TPU nanocomposites where it is known that the type of CNC extracted play an influential role in the rheological behavior of the CNC/TPU nanocomposites film. It has been successfully obtained mixed acid CNC with the length of 251 ±89 nm while having the onset degradation temperature of 332 °C, exhibiting a high thermal stability mixed acid CNC. After the incorporation of CNC into base TPU matrix, it has been shown that 1 wt% CNC loading portrays the highest reinforcement in terms of tensile stress for all extracted CNC/TPU nanocomposites. In terms of rheological properties, most of the fabricated CNC/TPU nanocomposites at different CNC loading displayed solid-like behavior albeit CNC produced by sulphuric acid hydrolysis incorporated into TPU. Meanwhile, 1 wt% CNC loading produced from sulphuric acid hydrolysis showed a liquid-like behavior believed to be due to the degradation of CNC during the fabrication of CNC/TPU nanocomposites. Hence, the idea of reducing solvent usage in the acid hydrolysis process to extract CNC has been proven to reduce the usage of acids in the process. In addition, the rheological properties of the CNC/TPU nanocomposites have provided a critical insight on the material behavior to give an understanding on the processing of CNC/TPU nanocomposites to be used as reference in the industrial scale.