Characterization and Comparison of Fluoroelastomer: Unfilled, Carbon Nanotube Filled (Unmodified, Acid or Base Surface Modified), and Carbon Black Using FTIR and Raman Spectroscopy

ABSTRACT A comprehensive set of samples was fabricated, consisting of carbon nanotube (CNT) filled fluoroelastomer (FE), surface‐modified CNT with acid modification (−COOH), referred to as MCNT, surface‐modified CNT with base modification (−OH), known as OHCNT, carbon black (CB) filled FE, and unfilled FE. These samples, designated as CNT/FE, MCNT/FE, OHCNT/FE, CB/FE, and FE, were subjected to detailed characterization using Fourier transform infrared (FTIR) and Raman spectroscopy to analyze their functional groups and crystallinity. The findings revealed several key insights: (1) The intensity of O–H and C=O peaks, as determined by FTIR, exhibited the following orders, respectively: MCNT/FE > OHCNT/FE > CB/FE > FE > CNT/FE and MCNT/FE > CB/FE > FE > OHCNT/FE > CNT/FE, indicating a significant presence of these functional groups in the surface‐modified samples. (2) Notably, the functional groups of the surface‐modified CNTs remained intact throughout the processes of compounding, curing, and post‐curing. (3) FTIR analysis revealed a notable reduction in crystallinity percentages across the α, β, and γ phases, with the following hierarchy observed: OHCNT/FE > MCNT/FE > CB/FE > CNT/FE > FE. This trend was further supported by additional rankings: MCNT/FE > CB/FE > OHCNT/FE > CNT/FE > FE, and MCNT/FE > OHCNT/FE > CNT/FE > CB/FE > FE. Similarly, Raman spectroscopy results corroborated these findings, demonstrating consistent crystallinity percentages in the following orders: MCNT/FE > CNT/FE > CB/FE > OHCNT/FE > FE; MCNT/FE > OHCNT/FE > CNT/FE > FE > CB/FE; and MCNT/FE > CNT/FE > OHCNT/FE > CB/FE > FE. (4) The crystalline phase percentages were ranked as γ > α > β in IR results and γ > β > α in Raman results, highlighting the dominance of the γ phase in the nanocomposites. (5) A redshifted peak at 1600 cm −1 for the G band was observed in all nano‐containing samples, attributed to the high shear mixing during compounding. (6) Among all samples, the FTIR intensities of aromatic C=C bond peaks of CNT followed the order: CNT/FE > MCNT/FE > OHCNT/FE > CB/FE > FE. This study underscores the significant impact of surface modification on the properties of CNT‐filled fluoroelastomers, providing valuable insights for future applications in advanced materials.