A soluble aromatic poly (amic acid) film was converted to a soluble polyimide by staging at 25°C intervals to 325°C and characterized at each interval by several analytical methods. The behavior observed was consistent with an interpretation that a reduction occurred in molecular weight of the poly (amic acid) during the initial stages of cure before the ultimate molecular weight was achieved as a polyimide. This interpretation was supported by the results of solution viscosity, gel permeation chromatography, low angle laser light scattering photometry, and infrared spectroscopy analyses. The results of this study serve to increase our fundamental understanding of how polyimides are thermally formed from poly (amic acid)s.
Dilute solution and melt viscosities of two poly(arylene ether ketones) were compared. One polymer contained all para linkages in the backbone and the other contained one meta linkage per repeat unit. Molecular dimensions were shown to agree with calculated values and entanglement spacings could be predicted using the semi-empirical formula of Graessley and Edwards. Frictional properties in the two melts differed considerably when compared in ‘corresponding states' at Tg+100°C.
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