Thermal degradation behaviour of aromatic poly(ester–imide) investigated by pyrolysis–GC/MS

Optical and Flame-Retardant Properties of a Series of Polyimides Containing Side Chained Bulky Phosphaphenanthrene Units

Among the multitude of polymers with carbon-based macromolecular architectures that easily ignite in certain applications where short circuits may occur, polyimide has evolved as a class of polymers with high thermal stability while exhibiting intrinsic flame retardancy at elevated temperatures via a char-forming mechanism. However, high amounts of aromatic rings in the macromolecular backbone are required for these results, which may affect other properties such as film-forming capacity or mechanical properties; thus, much work has been done to structurally derivatize or make hybrid polyimide systems. In this respect, flexible polyimide films (PI(1–4)) containing bulky 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) units have been developed starting from commercial dianhydrides and an aromatic diamine containing two side chain bulky DOPO groups. The chemical structure of PI(1–4)) was characterized by 1H NMR, 13C NMR and 31P NMR spectroscopy. The optical properties, including absorption and luminescence spectra of these polymers, were analyzed. All polyimides containing DOPO derivatives emitted blue light with an emission maxima in the range of 340–445 nm, in solvents such as N,N-dimethylformamide, N-methyl-2-pyrrolidone, chloroform, and N,N-dimethylacetamide, while green light emission (λem = 487 nm for PI-4) was evidenced in a thin-film state. The thermal decomposition mechanism and flame-retardant behavior of the resulting materials were investigated by pyrolysis-gas-chromatography spectrometry (Py-GC), scanning electron microscopy (SEM), EDX maps and FTIR spectroscopy. The residues resulting from the TGA experiments were examined by SEM microscopy images and FTIR spectra to understand the pyrolysis mechanism.

Self-Diagnostic Polymers-Inline Detection of Thermal Degradation of Unsaturated Poly(ester imide)s

Monitoring polymer degradation is an important quest, particularly relevant for industry. Although many indirect methodologies for assessing polymer degradation exist, only few are applicable for an inline-monitoring via optic detection-systems. An inline-monitoring system is introduced for the thermal degradation of crosslinked poly(ester imide)s (PEIs) by embedding trifluoroacetyl functionalized stilbene molecules, serving as chemosensors to track the release of generated alcoholic byproducts. Nucleophilic addition of an alcohol to the sensors trifluoroacetyl functionality triggers hemiacetal formation which is accompanied by significant changes in optical properties, in turn allowing monitoring of sensor activation by direct spectroscopy. Fluorescence spectroscopy offers an easy detection tool for the inline thermal monitoring of PEI-degradation.

Quantitative Analysis of Red Phosphorus in Polypropylene by Evolved Gas Analysis Mass Spectrometry

Quantitative analysis of red phosphorus in polypropylene was studied using a temperature programmable pyrolyzer in combination with a mass spectrometer. Evolved gas analysis (EGA) profiles were obtained by continuous measurements of evolved gases from a sample while heating the sample at a constant heating rate. During heating of the sample, red phosphorus sublimates into P₄ molecules, which have characteristic ions (m/z 31, 62, 93 and 124). Red phosphorus in polypropylene was determined from the m/z 62 ion peak area of the EGA profile with good reproducibility. The determined value was close to the value of original formulation and to the one determined by pyrolysis-GC/MS.