Polyimides temperature/humidity exposure

Figure 3.27 Increase in capacitance for polyimide on temperature/humidity exposure.

Adhesion of polyimides to ceramics Effects of aminopropyltriethoxysilane and temperature and humidity exposure on adhesion... 

The results of a program to evaluate high-temperature adhesives for extended service have been reported by Hendricks et al" They used titanium lap shear coupons, prepared with either a polyphenylquinoxaline adhesive or a thermoplastic polyimide adhesive, to study the effects of thermal and humidity exposures. The polyphenylquinoxaline was affected by exposure... 

Abstract—The effects of both y-aminopropyltriethoxysilane (APS) and elevated temperature and humidity (T H) exposure on the adhesion of pyromellitic dianhydride-oxydianiline polyimide to SiO , AkOi, and MgO were studied using XPS, SEM, and peel test. Adhesion and T H stability of PMDA-ODA on Si02 is significantly improved when APS is used at the interface, while no significant improvement is observed for AkO, or MgO. XPS analysis of the surfaces showed no retention of APS on AkO, or MgO, while Si02 did retain APS, as is expected. The APS retention is affected by surface treatment of the oxide prior to APS application. 

Polyimide adhesion to the substrate surface is not only important initially after the interface preparation, but also after exposure for extended times to elevated temperature and humidity (T H) conditions. As Plueddemann [7] states Water molecules diffuse through any plastic and thus will reach the interface in composites exposed to humid environment. Individual water molecules, however, are relatively harmless at the interface unless they are capable of clustering into a liquid phase. The concentration of water at the interface is not determined by the rate of permeation of the water through the polymer matrix (silicones and... 

The surface chemical structure of several thin polyimide films formed by curing of polyamic acid resins was studied using X-ray photoelectron spectroscopy (ESCA or XPS). The surface modifications of one of the polymer systems after exposure to KOH, after exposure to temperature and humidity, after exposure to boiling water, and after exposure to O2 and 02/CF plasmas were also evaluated. The results showed imide bond formation for all cured polyimide systems. It was found that (a) K on the surface of the polyamic acid alters the "normal" imidization process, (b) cured polyimide surfaces are not invarient after T H and boiling water exposures, and (c) extensive modifications of cured polyimide surfaces occur after exposures to plasma environments. Very complex surfaces for these polymer films were illustrated by the C Is, 0 Is, N Is and F Is line characteristics. 

In Table 1, the moisture uptake of cured and uncured Navy P3-2300-PE resin after 24 hours of immersion is compared to a number of other high-temperature polymer resins. The moisture uptake of the Navy P3 oligomer is nearly identical to that of the commercial P3 thermoplastic. Other commercial thermoplastics, such as poly(ether ether ketone), with very similar chemical compositions, exhibit similarly low levels of moisture uptake. On the other hand, the Navy P3 resins absorbs about 85% less water than the commercial polyimide Kapton HN. Since thermosetting phenyl ethynyl end-capped polyimides have moisture uptake characteristics that are similar to Kapton HN, with around 3% weight gain on exposure to 95% relative humidity (77), void-free composites based on Navy P3 resins should exhibit greatly reduced moisture uptake compared to those based on thermosetting polyimides. 

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