Enhancement of mechanical properties of PAN fibers using SWCNT
Carbon fibers offer lightweight and high strength/high modulus based on the raw material used to produce the fibers. Polyacrylonitrile (PAN) based carbon fibers showcase high tensile strength and lower modulus compared to pitch based fibers. Researchers have found that carbon nanotube reinforced fibers showcase an enhanced mechanical and electrical properties of such fibers.
A group of researchers at Soochow University, China have showcased a method for electrospinning SWCNT/PAN composite fibers with enhanced alignment using their modified parallel electrode method, which incorporates an additional positively charged ring (electrode) between the electrodes. This addition to the electrospinning design has proven improved alignment and uniformity of the spun fibers.
The composite fibers showcased enhanced mechanical and electrical properties. The tensile strength of the 1 wt% SWCNT composite fiber showcased an enhancement of 38% in tensile strength and a decrease in elongation of ~31%. It was also noted that the dimeter and roughness of the fibers increased with the increase in SWCNT content. The roughness was attributed to the agglomeration of the nanotubes. The nanotubes used in this study were functionalised with -COOH groups. This kind of treatment is necessary to obtain homogeneous dispersion of nanotubes throughout the dope.
Dr Smalley’s group at Rice University observed that the HIPCO® SWCNT reinforcement decreases the dissolution of the PAN fibers in solvents such as Dimethylformamide (DMF). Additionally, this interaction forbids the PAN molecules from shrinkage, consequently reducing the tension required in the stabilization(oxidation) process of carbon fiber production from PAN fibers, or at tension, enhancing orientation and modulus.
The group showcased a ~56% enhancement in tensile strength at 5wt% load (0.23GPa to 0.36GPa) and an increase in glass transition temperature from 103℃ to 143℃. An enhancement in modulus too was seen from 7.9GPa for pure PAN fibers to 16.2GPa for a 10wt% SWCNT reinforcement, corresponding to ~205 percentage enhancement.
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