Decomposition and Flammability of Polyimide Graphene Composites

Polyimide-graphene composites were synthesized by in-situ condensation polymerization and the thermal stability and decomposition behavior of the composites were studied. Polyimides, because of their aromatic backbone, are a class of fire-retardant polymers. Their high char retention ≥50% at testing temperatures ≥600 °C makes them thermally stable polymers. The effect of nanographene sheets on the decomposition behavior of polyimide is presented in this paper. It is shown that the reinforcement of polyimide with nanographene sheets significantly decreased the rate of decomposition of polyimide and increased the char retention of the composite. Thermogravimetric analysis data were used to assess the thermal stability, rate of mass loss and predicted limiting oxygen index of the neat polyimide and composites. Results obtained showed around a 43% decrease in the rate of polyimide degradation at 50 wt.% graphene loading. The limiting oxygen index of the polyimide nanocomposite was calculated by using the char retention, and it was found to increase by up to 24% at 50 wt.% graphene loading over that for the neat matrix.

High-performance wholly aromatic polyamide–hydrazides

The review summarizes the various methods of preparing wholly aromatic polyamide–hydrazides (PAHs). Polyhydrazides are a class of polymers that possess in their repeating units one amide (–NHOC–) and one hydrazide (–CONHNHOC–) linking bond between appropriate aromatic nuclei. The review provides several figures of different molecular structures of PAH and expounds the methods of polymerization, low, high temperature, and phosphorylation polycondensation methods. Polyhydrazides exhibit some unique and potentially useful properties such as outstanding thermal and thermo-oxidative resistance, very high mechanical strength, and ultrahigh moduli. PAHs undergo structural transformation into poly(amide-1,3,4-oxadiazole)s upon heating, which are also considered highly thermally stable polymers. The review presents a description of the structure–property relation of PAHs. The application of PAHs in reverse osmosis applications has been discussed, as well as the preparation of fibers and metallized PAHs films. Modification of the PAH with carbon nanotubes and graphene and the future prospects for PAHs were introduced with comprehensive references pertaining to this area of research.

Novel Polymer Composites on the Basis of Arylalicyclic Polyimide Blends. I. Polyimide/Polycarbonate & Polyimide/Polysulphone Blends

The new composite materials based on dianhydride of tricyclodecentetracarbon acid and oxydianiline with two other thermally stable polymers, such as polycarbonate and polysulphone, are being reported. The synthesis of the polyimide blends was done through two ways: mechanical mixing of two homopolymer ingredients; and the so-called chemical mixing of polyimide comonomers with the above-mentioned polymers. The physico-chemical and physico-mechanical properties have been manifested in a broadening of their performance characteristics. It was not found any physical-chemical interactions between the two ingredients of the blend, which indicates the formation of a typical compatible polymer blend with an appropriate miscibility. Such new polyimide composite could be an ideal candidate for the preparation of reflective and conductive metallized polyimide blend films with wide mechanical performances.