Tensile properties of carbon fibers from acrylic fibers stabilized under isothermal conditions

Abstract

SynopsisA series of carbon fibers were prepared from the acrylic fibers thermally stabilized in air under various temperature-time conditions, and the relation between the extent of stabilization and the tensile properties of carbon fibers was investigated. The density of stabilized fibers was adopted as a measure of the extent of stabilization. The tensile modulus of carbon fibers changed dependently on stabilization temperature. However, the variation of the tensile modulus of carbon fibers with the density of stabilized fibers was small if stabilization temperature was constant. In the relation between the tensile strength of carbon fibers and the density of stabilized fibers, a feature depending on stabilization temperature was not evident, and the tensile strength of carbon fibers showed a maximum in the density range from about 1.34 to 1.39 g/cm3 of stabilized fibers.

Influence of processing parameters on the properties of carbon fibres – an overview

“…Because of different mass and heat transport phenomena, the results cannot be directly transferred to a continuous conversion of fibres . Additionally, process investigations have been performed partly for batch and partly for continuous processes . This kind of process control leads to varying processes differing for instance in stabilisation (stepwise temperature treatment in continuous processes and linear change of temperature in batch processes) and can therefore hardly be compared.…”

“…An increasing temperature leads to a cyclisation and oxidation reaction of polyacrylonitrile resulting in a ladder structure and an increase in density . A resulting density of the stabilised fibre of 1.34–1.39 g/cm 3 leads to high tensile strengths . Contrary, the density of carbon fibres decreases steadily with increasing density of stabilised fibres .…”

“…The stabilisation reactions result in a release of exothermic heat which needs to be carefully adjusted to prevent fibre burn off and breakage. It can be influenced by process parameters like heating rate, temperature time profile, tension and atmosphere [1,54,57,59,63,67,70,71,[103][104][105]. To manufacture carbon fibres with improved mechanical properties, several final temperatures have been tested ranging from 270 to 380°C (not less than 240°C) [53,54,106,107].…”

An investigation on structure characterization of thermally stabilized polyacrylonitrile precursor fibers pretreated with guanidine carbonate prior to carbonization

“…The results reported by the published literature shows the decrease of the density of the carbon fibers with increasing density of the thermally stabilized precursor fibers [56]. This suggests the formation of microvoids in carbon fibers leading to significant increases with increasing density of the thermally stabilized fibers, which ultimately results in the reduction of the tensile strength of carbon fibers.…”

“…The results show the continuous increase of density with stabilization time. Takaku et al [56] reported the increase of density with increasing stabilization temperature. It was shown that high stabilization temperatures resulted in shorter stabilization times to reach a certain value of density.…”