Polyimides and polyamide-imides

In this paper we use dielectric measurements to calculate the polarizability of absorbed water in a series of aromatic polyimides and polyamide-imides. In the relatively non-polar polyimides, the absorbed water has a dipole moment close to that of free water (/i - 1.88 Debyes). This value drops to less than 0.4/x for polyamide-imides. The decrease may be attributed to hydrogen-bonded water in the very polar polyamide-imides. In addition, the "group" dipole moment for amide is calculated and found to be greater than the dipole moment of free water. 

Dielectric measurements were used to calculate the relative polarizability of absorbed water in a series of polyimides and polyamide-imides. The effective dipole moment of the absorbed water varied from 1.8 Debyes to 0.7 Debyes. This corresponds to... 

The polyimides and polyamide-imides are produced by condensation reactions which give off volatile low-molecular-weight by-products. The polybismalemimides may however be produced by rearrangement polymerization with no formation of by-products. The starting materials in this case are the bismaleimides, which are synthesized by the reaction of maleic anhydride with diamines (Figure 4.21). 

The Kinel materials produced by Rhone-Poulenc are polybismaleinimides of the type shown in Figure 4.22. These materials have chain-end double bonds, as explained previously, can be processed like conventional thermosetting plastics. The properties of the cured polymers are broadly similar to the polyimides and polyamide-imides. Molding temperatures are usually from 200°C to 260°C. Post-curing at 250°C for about 8 h is necessary to obtain the optimum mechanical properties. 

Polyimide and polyamide-imide Excellent thermal properties Good composite properties Good electrical properties Good fire properties Restricted choice of color Arc resistance Acid and alkali resistance... 

Method 3.6 Determination of Amino Groups in Aromatic Polyamides, Polyimides and Polyamides-imides. Potassium Hydroxide Fusion Gas Chromatography [158, 159]... 

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