Thermomechanical behaviour of poly[acrylonitrile‐co‐(methyl acrylate)] fibres oxidatively treated at temperatures up to 180 °C

Abstract

PAN fibres, consisting of poly[acrylonitrile-co-(methyl acrylate)], were oxidatively heat treated at low temperatures (up to 180 • C), during which the basic macromolecular backbone was not cyclized. The change of length of the fibres was determined under various treatment conditions (ie temperature, time, stress applied). Prolonged heat treatment resulted in lower tensile strength of the fibres. The pristine and treated fibres were characterized by Fourier-transform infrared (FTIR), NMR and UV-visible spectroscopy and by TGA, and the results were used for representing the different regions according to chemical aspects in a plot of temperature versus time; this is very important for the whole treatment process. A shrinkage model was proposed, having both scientific and technical importance. The change in activation volume of shrinkage of fibres with temperature, calculated from this model, is indicative of the physical transitions taking place at the molecular scale.

PAN monofilament in nanoscale: a novel approach

“…In the mean time the gathered data from DSC curves of PAN all samples with take-up velocity between 22.5 m/min and 67.7 m/min are summarized in Table 4. The glass transition temperature (T g ) has no substantial change with increasing take up speed and approximately is equal to 100 o C. An exothermic peak present in DSC curve presumably can be attributed to dehydrogenation and cyclization reactions [14,15,16]. These chemical reactions must be conducted for a slow heat release.…”

A Novel Method for Investigation of Entropic Stress in Prestabilization of PAN‐Based Precursor Fibers

“…42 As the temperature is raised, due to loosening of intermolecular dipole-dipole interactions, adjacent nitrile groups of the same macromolecule repel each other and these interactions increase activation volume. 20,35,43,44 Rubbery flow is occurred with contribution of imposed stresses and fibers start to elongate. Before this region, fibers show shrinkage behavior due to lower applied stress (Fig.…”

“…These reactions result in formation of C=C bonds in the polymer that changes the flexibility of macromolecular backbone. 20 Since the chemical shrinkage occurs due to the cyclization reaction, structural changes before the onset of cyclization can be considered to be effective parameters on physical shrinkage and entropic stress.…”

“…6,[12][13][14][15][16] In the second method, fibers are restrained by a constant force during heat treatment. [17][18][19][20][21] In the third method, stretching force is applied on PAN fibers by controlling the speed differences between the feed rollers and the take-up rollers in the continuous prestabilization process. 5,[22][23][24][25][26][27][28] However in prior studies, certain load and the stretching forces have been selected independent from entropic stress that causes fiber shrinkage.…”

Strategies towards Novel Carbon Fiber Precursors: the Research Results on the Synthesis of PAN Copolymers via AGET ATRP and on Lignin as a Precursor

“…The most important peaks are at 2950 cm -1 that is attributed to the -CH 2 -and CH 3 -units, at 2240 cm -1 that is ascribed to the nitrile group, C≡N, at 1740 cm -1 due to carbonyl groups, C=O, between 1470 and 1370 cm -1 that is attributed to various C-H absorption modes, in the ranges of 1240-1060 cm -1 and 920-880 cm -1 that both ascribed to various absorption modes of C-O-C ester bonds [17]. Their presence indicate that the polymer contains both AN (i.e.…”