The Impact of Shear and Elongational Forces on Structural Formation of Polyacrylonitrile/Carbon Nanotubes Composite Fibers during Wet Spinning Process.

Hamideh Mirbaha,Luca Valentini,Gabriele Greco,Parviz Nourpanah,Nicola Pugno,Shahram Arbab,Paolo Scardi,Silvia Bittolo Bon,Mirco D’Incau

doi:10.3390/ma12172797

Abstract

Wet spinning of polyacrylonitrile/carbon nanotubes (PAN/CNT) composite fibers was studied and the effect of spinning conditions on structure and properties of as-spun fibers influenced by the presence of CNTs investigated. Unlike PAN fibers, shear force had a larger effect on crystalline structure and physical and mechanical properties of PAN/CNT composite fibers compared to the elongational force inside a coagulation bath. Under shear force CNTs induced nucleation of new crystals, whereas under elongational force nucleation of new crystals were hindered but the already formed crystals grew bigger. To our knowledge, this key effect has not been reported elsewhere. At different shear rates, strength, Young’s modulus and strain at break of PAN/CNT as-spun fibers were improved up to 20% compared to PAN fibers. Application of jet stretch had less influence on physical and mechanical properties of PAN/CNT fibers compared to PAN fibers. However, the improvement of interphase between polymer chains and CNTs as a result of chain orientation may have contributed to enhancement of Young’s modulus of jet stretched composite fibers.

Highlights

Carbon nanotubes (CNTs) have numerous applications due to their extraordinary properties, among which production of composite fibers based on polymer/CNT with ability to improve physical, mechanical, thermal, electrical and sound absorption properties can be noted [1,2,3,4,5,6,7,8,9]
There has been some research in recent years on polyacrylonitrile/carbon nanotubes (PAN/CNT) composite fibers, with a focus on the effect of different CNT types, content and post-processing on the structure and properties of final PAN/CNT fibers or their conversion to carbon fibers [1,6,10]
The crystallite sizes of jet stretched fibers were not bigger than freely spun fibers at high shear rates of 19,000 and 28,000 s−1. These results showed the stronger effect of shear force on growth of crystallites and the bigger effect of elongational force on the crystallinity of PAN reference fibers

Summary

Introduction

Carbon nanotubes (CNTs) have numerous applications due to their extraordinary properties, among which production of composite fibers based on polymer/CNT with ability to improve physical, mechanical, thermal, electrical and sound absorption properties can be noted [1,2,3,4,5,6,7,8,9]. Since the parameters affecting structure formation during spinning process are diverse, successful production of PAN/CNT composite fibers with desired properties requires intensive research and correlation of the results. Lower structural order, more defects and lack of crystalline interphase can be expected In such conditions, exploiting desirable properties of CNTs inside fibers is not possible. There has been some research in recent years on PAN/CNT composite fibers, with a focus on the effect of different CNT types, content and post-processing on the structure and properties of final PAN/CNT fibers or their conversion to carbon fibers [1,6,10]. Studying the structure formation of PAN/CNT composite fibers in early stages of production and the effect of different parameters in the spinning process is the focus of this paper

Methods

Results

Conclusion