Thermal, Mechanical, and Microstructural Study of PBO Fiber during Carbonization.

Weizhe Hao,Xuejun Zhang,Yanhong Tian

doi:10.3390/ma12040608

Weizhe Hao, Xuejun Zhang + Show 1 more

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https://doi.org/10.3390/ma12040608

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Abstract

Poly(p-phenylene benzobisoxazole) (PBO) fiber shows fascinating properties including excellent mechanical performance, high crystallinity, and fairly good heat resistance as a kind of polymer fiber. Its properties make it a possible candidate as a precursor of carbon fiber. This paper mainly investigates the possibility of yielding carbon fiber from PBO by direct carbonization using a continuous process and multiple properties of yielded fiber treated under different heat treatment temperature (HTT). The results show that PBO fiber was able to sustain an HTT as high as 1400 °C under the inert atmosphere and that the shape of fiber was still preserved without failure. Using thermal gravimetric analysis (TGA) and TGA coupled with mass spectroscopy (TGA-MS), it was found that a significant mass loss procedure happened around 723.3 °C, along with the emission of various small molecules. The mechanical performance first suffered a decrease due to the rupture of the PBO structure and then slightly increased because of the generating of graphite crystallite based on the broken structure of PBO. It was observed that PBO’s microstructure transformed gradually to that of carbonaceous material, which could be the reason why the change of mechanical performance happened.

Highlights

Carbon fiber has been paid much more attention recently due to its excellent properties such as high tensile strength, tunable Young’s modulus, extraordinary chemical stability, and heat resistance [1,2,3,4], which has broadened its application field to include aerospace, commercial industries, etc. [5]
This material is suitable as a kind of fiber reinforcement for producing fiber reinforced plastics (FRP) especially [6,7,8]
Using aged PBO fibers as the raw material, the purpose of this paper was to study the mechanism of PBO during carbonization process as well as the capability of obtaining carbon fiber through heat treatment of a PBO fiber

Summary

Introduction

Carbon fiber has been paid much more attention recently due to its excellent properties such as high tensile strength, tunable Young’s modulus, extraordinary chemical stability, and heat resistance [1,2,3,4], which has broadened its application field to include aerospace, commercial industries, etc. [5]. The commonly used precursor contains polyacrylonitrile (PAN) [10], pitch [11,12,13], and rayon [7,14,15]. Among those polymer precursors, PAN is mostly adopted to produce carbon fiber, and PAN-based carbon fiber (PAN-CF) takes up approximately 90% of the global market [10]. Traditional PAN-CF techniques mainly contains three steps: pre-oxidation, carbonization, and graphitization [16]. The manufacturing of a PAN precursor is a high-cost step which takes up over 50% of the production cost of PAN-based carbon fiber [19]. The pre-oxidation process requires prolonged treating time and massive energy, which makes this procedure take up approximately 20% of the total cost [20]

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