Polyimides glass transition temperature

Thermal Properties. Each of the polyimide film samples was evaluated by differential scanning calorimetry to determine the glass transition temperature (Table I). The general observation is that the BTDA-ODA polyimide films have a higher glass transition temperature than the BDSDA-ODA polyimide films whether they are nonmodifled or are modified with cobalt chloride. This is in agreement with the work of Frye ( ) in which the dianhydride moiety, not the dieunine, was found to control the polyimide glass transition temperature. 

Since successful commercialization of Kapton by Du Pont Company in the 1960s (10), numerous compositions of polyimide and various new methods of syntheses have been described in the Hterature (1—5). A successful result for each method depends on the nature of the chemical components involved in the system, including monomers, intermediates, solvents, and the polyimide products, as well as on physical conditions during the synthesis. Properties such as monomer reactivity and solubiHty, and the glass-transition temperature,T, crystallinity, T, and melt viscosity of the polyimide products ultimately determine the effectiveness of each process. Accordingly, proper selection of synthetic method is often critical for preparation of polyimides of a given chemical composition. 

Relatively few processible polyimides, particularly at a reasonable cost and iu rehable supply, are available commercially. Users of polyimides may have to produce iutractable polyimides by themselves in situ according to methods discussed earlier, or synthesize polyimides of unique compositions iu order to meet property requirements such as thermal and thermoxidative stabilities, mechanical and electrical properties, physical properties such as glass-transition temperature, crystalline melting temperature, density, solubility, optical properties, etc. It is, therefore, essential to thoroughly understand the stmcture—property relationships of polyimide systems, and excellent review articles are available (1—5,92). 

Other Polyimides. In 1979, Rohm Haas introduced Kamax resin, which was thought to be an /V-methylamine imidization product of poly(methyl methacrylate) (118). The product was then withdrawn, but was reintroduced in the late 1980s. The partly imidized resins are similar to poly(methyl methacrylate) but have a higher glass-transition temperature. 

Acetylene terminated polyimide prepolymers have many advantages over conventional polyimides in the areas of processing and solvent resistance. In addition, the presence of the isoimide structure further extends the the utility of these systems by modification of the solubility properties and glass transition temperature. 

Values of the upper glass transition temperatures of the siloxane modified polyimides were found to be a function of both the level of incorporated siloxane as well as the siloxane molecular weight (Table II). The upper transition temperature of the solution... 

A,A -di(/>-dimethylamino-benzyl) derivatives of di(imidazolidinylidene)gold(i) salts were polymerized into polyimides by condensation with arene-tetracarboxylic anhydrides. The products are tough, but flexible, and have high glass transition temperatures and high thermal stability. Yellow films of the materials are transparent above 365 nm.279... 

Polyimides offer outstanding properties, such as glass transition temperature, oxidative stability, toughness, adhesion, permeability, and the capability of being fabricated into useful products. It is this versatility that has established the reputation of polyimides for many applications.6... 

As films, certain polyimides remain functional at cryogenic temperatures, -269°C for example. Typical glass transition temperatures for polyimides are 300°C and above. 

Glassy polymers with much higher glass transition temperatures and more rigid polymer chains than rubbery polymers have been extensively used as the continuous polymer matrices in the zeolite/polymer mixed-matrix membranes. Typical glassy polymers in the mixed-matrix membranes include cellulose acetate, polysul-fone, polyethersulfone, polyimides, polyetherimides, polyvinyl alcohol, Nafion , poly(4-methyl-2-pentyne), etc. 

The data indicate that the properties of the lower glass transition temperature metal ion modified polyimides are altered more than the properties of the higher glass transition temperature metal ion modified polyimides. Extraction removes both cobalt and chlorine from the films and slightly increases bulk thermal stability and both surface resistivity and bulk electrical resistivity. Details pertaining to the structure, analysis and properties of these novel gradient composites are discussed. 

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