The impact of guanidine carbonate incorporation on the molecular structure of polyacrylonitrile precursor fiber stabilized by a multistep heat treatment strategy

Abstract

Thermal-oxidative stabilization of the polyacrylonitrile (PAN) precursor was performed employing a multi-step heat treatment strategy in an air circulating furnace. In this approach, the applied temperature was gradually increased from 200 degrees C to 250 degrees C employing several stages for different stabilization durations. Fifteen percent guanidine carbonate (GC) was found as optimum to incorporate with the PAN precursor fibers to accelerate the thermal-oxidative stabilization process. Characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile strength, volume density, linear density, fiber thickness, and burning test have been performed to monitor the changes in PAN structure. Test results of the stabilized samples were compared with the reference sample results to demonstrate the accelerating effect of GC integration. Findings showed that GC pretreatment enhanced and accelerated the cyclization of nitrile groups in the PAN polymer structure and allowed the quicker formation of a thermally stable structure. The analysis of the experimental results revealed that GC integration and employing the multi-step heat treatment strategy helps greatly to cut the overall PAN-based carbon fiber production cost.