Thermal Analysis and Crystal Structure of Poly(Acrylonitrile-Co-Itaconic Acid) Copolymers Synthesized in Water.

Hailong Zhang,Lianghua Xu,Ling Quan,Fengjun Shi,Yuping Tong,Aijun Gao

doi:10.3390/polym12010221

Abstract

The composition and structure of polyacrylonitrile (PAN) precursors play an important role during thermal stabilization, which influences the properties of the resulting carbon fibers. In this paper, PAN homopolymer and PAN-itaconic (IA) copolymers with different IA contents were synthesized by aqueous phase precipitation polymerization. The effects of IA content on the structure and thermal properties were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The morphology of PAN polymers showed that the average size of the PAN particles increased with the increase of IA content in the feed. The content of the IA comonomer on the copolymers was quantitatively characterized by the relative absorbance intensity (A1735/A2243) in FTIR spectrum. With the increase of IA content in the feed, PAN-IA copolymers exhibited lower degree of crystallinity and crystal size than the control PAN homopolymer. The results from DSC curves indicated that PAN-IA1.0 copolymers had lower initial exothermic temperature (192.4 °C) and velocity of evolving heat (6.33 J g−1 °C−1) in comparison with PAN homopolymer (Ti = 238.1 °C and ΔH/ΔT = 34.6 J g−1 °C−1) in an air atmosphere. TGA results suggested that PAN-IA1.0 copolymers had higher thermal stability than PAN homopolymer, which can form a ladder structure easier during thermal processing. Therefore, PAN-IA1.0 copolymers would be a suitable candidate for preparing high performance PAN based carbon fibers.

Highlights

Carbon fibers have gained tremendous attention because of their excellent mechanical properties and low density, and can be used in the industrial field, aerospace, defense areas, and civil engineering [1,2,3].Its precursor materials, such as polyacrylonitrile (PAN), pitch and rayon, need to undergo a series of processes to be converted into carbon fibers, including drawing and heat treatment [4,5,6]
We studied the effects of itaconic acid (IA) content on the particle morphology and crystal structure for PAN-IA copolymers prepared by aqueous phase precipitation polymerization
These results indicate that the relative content of IA comonomer could change the morphology of PAN, which might affect the crystal structure owing to decrease of the adjacent interaction of nitrile groups [40]

Summary

Introduction

Carbon fibers have gained tremendous attention because of their excellent mechanical properties and low density, and can be used in the industrial field, aerospace, defense areas, and civil engineering [1,2,3]. Its precursor materials, such as polyacrylonitrile (PAN), pitch and rayon, need to undergo a series of processes to be converted into carbon fibers, including drawing and heat treatment [4,5,6]. Fox regarded that the PAN fibers produced by Liao et al [14]

Methods

Results

Conclusion