Multi-scale and multi-technical analysis of the thermal degradation of poly(ether imide)

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. A B S T R A C TThe thermal degradation of PEI has been studied in wide ranges of temperature (between 180 and 250°C) and oxygen partial pressure (between 0.21 and 50 bars). On one hand, the chemical ageing mechanisms have been analysed and elucidated by FTIR spectrophotometry and by differential calorimetry (DSC) on sufficiently thin PEI films (between 10 and 60 μm thickness) to be totally free of the effects of oxygen diffusion. As expected, and by analogy with other aromatic polymers of similar chemical structure, oxidation occurs preferentially on the methyl groups of the isopropylidene unit of the bisphenol A part, thus causing the disappearance of their characteristic IR absorption band at 2970 cm −1 and the growth of a new IR absorption band at 3350 cm −1 , attributed to alcohols. In addition, oxidation leads successively to a relative predominance of chain scissions and crosslinking, resulting in a non-monotonic change of T g . On the other hand, the consequences of oxidation on the elastic properties have been analysed and elucidated by micro-indentation on polished cross-sections of PEI plates of 3 mm thickness. The diffusion control of oxidation leads to the development of profiles of Young's modulus within the sample thickness, which correlate perfectly with the changes in chemical structure determined by FTIR spectrophotometry. However, the increase in Young's modulus in the superficial oxidized layer is not the direct consequence of oxidation but of a physical ageing.

Experimental correlation of rheological relaxation and interface healing times in welding thermoplastic PEKK composites

“…Figure 2 shows an important increase in the storage modulus at high temperature which could be attributed to a decrease in chain mobility and confirms crosslinking of the materials. This crosslinking seems also to be faster at higher temperatures validating that this is a thermo-dependent phenomenon as already demonstrated for PEKK [21] and PEEK [23]. As both the storage and loss moduli increase with dwell time, the intersection between G and G" takes place at lower frequencies and the relaxation times are consequently higher.…”

Ageing Assessment of XLPE LV Cables for Nuclear Applications Through Physico-Chemical and Electrical Measurements

“…A pause of 30 s was systematically applied between the loading and unloading. The indentation operating software gives directly the values of the reduced modulus (E r ) of the material and its Vickers hardness (HV), which are calculated according to the Oliver and Pharr's method [34], [35], as follows:…”

A New Kinetic Modeling Approach for Predicting the Lifetime of ATH-Filled Silane Cross-Linked Polyethylene in a Nuclear Environment

“…As shown in previous studies [ 45 , 46 ], can roughly be associated with the Young’s modulus of the composite material under consideration.…”

“…A pause of 10 s was systematically applied between loading and unloading to eliminate the viscous response of the Si-XLPE matrix. The Indentation 4.37 operating software gave the value of the reduced modulus of the material directly, calculated according to Oliver and Pharr’s method [ 44 , 45 , 46 ]: where is the slope at the origin point of the unloading curve, β is a shape factor depending on the indenter type ( 1.012 for a Vickers tip), and is the contact area between the indenter and the sample, projected perpendicularly to the indenter axis on the sample surface: , where a is the side length of the projected square. This last quantity is also directly provided by the operating software.…”