Physical properties of polyimides

TABLE 2. Physical properties of polyimides as liquid crystal aligning films prepared by heating A-methyl-pyrrolidone and y-butyrolactone, 8 2, respectively, with polyamic acids described in Table 1. 

Table 4. Selected Physical Properties of Polyimide Films Derived from Nonphotosensitive Polyimide Precursors...

Chemical and Physical Properties of Polyimides Biomedical and Engineering Applications... 

Yudin, V. E. and V. M. Svedichnyi. 2010. Effect of the structure and shape of filler nanoparticles on the physical properties of polyimide composites. Russian Journal of General Chemistry 80 (10) (November 26) 2157-2169. doi 10.1134/S1070363210100452. http //www.springerlink.coni/index/10.1134/S1070363210100452. 

NLO chromophores have recently been incorporated in polyimides as side-chain and main-chain systems [74-76]. These samples in general exhibit excellent temporal stability at elevated temperatures (e.g.. long-term stability of over KXX) h at I20°C [75]). Relatively large NLO responses have also been reported (e.g., r y of 13 pm/V at 1.3 ixm [74]) as the materials no longer suffer from limited solubility. The excellent chemical and physical properties of polyimides in conjunction with high chromophore loading make these polyimide-based materials very promising for EO applications. 

Experimental results are presented that show that high doses of electron radiation combined with thermal cycling can significantly change the mechanical and physical properties of graphite fiber-reinforced polymer-matrix composites. Polymeric materials examined have included 121 °C and 177°C cure epoxies, polyimide, amorphous thermoplastic, and semicrystalline thermoplastics. Composite panels fabricated and tested included four-ply unidirectional, four-ply [0,90, 90,0] and eight-ply quasi-isotropic [0/ 45/90]s. Test specimens with fiber orientations of [10] and [45] were cut from the unidirectional panels to determine shear properties. Mechanical and physical property tests were conducted at cold (-157°C), room (24°C) and elevated (121°C) temperatures. 

The synthesis of well-defined LCB polymers have progressed considerably beyond the original star polymers prepared by anionic polymerization between 1970 and 1980. Characterization of these new polymers has often been limited to NMR and SEC analysis. The physical properties of these polymers in dilute solution and in the bulk merit attention, especially in the case of completely new architectures such as the dendritic polymers. Many other branched polymers have been prepared, e.g. rigid polymers like nylon [123], polyimide [124] poly(aspartite) [125] and branched poly(thiophene) [126], There seems to be ample room for further development via the use of dendrimers and hyperbran-... 

TABLE 1. Physical Properties of d-Polyimides Prepared by Condensing Pyromellitic Dianhydride with Deuterated o-Tolidine and then Heating to 200-300°C... 

In response to the simultaneous needs for improving epoxy properties and decreasing the cost of polyimide based materials, several approaches have been attempted to combine the two. The physical addition of polyimide to epoxy has been limited by the fundamental immiscibility of polymers containing imide... 

The physical properties of systems having imide groups incorporated with epoxy resin was not seen until much later. Researchers in Korea performed microscopic analysis of commercially available polyetherimide (ULTEM1000) modified epoxy resins [40]. In their work, electron micrographs of the systems showed a two phase system even though their systems were limited to polyimide contents of less then 10 wt%. Compatibilizing polyesterimides with polyetherimides in order to fabricate in situ epoxy composites was addressed by Seo et al. [41]. 

Another important factor that would be important in many of the applications where epoxy-polyimide could be used is the dielectric constant. The high dielectric values of epoxy, in the range 3.5-10, result from the many hydroxyl groups in cured epoxy resin and preclude its use in electrically demanding applications. Polyimide with its excellent physical properties of high temperature stability and low dielectric constant make it an ideal candidate to replace the glass reinforcement in epoxy printed circuit boards. 

The chemical and physical properties of each of these window materials vary widely. For example, polyimide is flexible, semitransparent, and chemically inert, but it has an upper working temperature of 673 K (for information about the properties of Kapton see http //www2.dupont. com/Kapton/en US / assets / downloads / pdf/ summaryofprop.pdf). Beryllium is stiff, has a low density, high thermal conductivity, and a moderate coefficient of thermal expansion it can be machined and is very stable mechanically and thermally. It also retains useful properties at both elevated and cryogenic temperatures. However, it does require a few safety-related handling requirements that are well documented (for detailed environmental safety and health information about beryllium see http //www.brushwellman.com). Nonetheless, as is stated in the Brush Wellman literature (for detailed environmental safety and health information about beryllium see http //www.brushwellman.com), "handling beryllium in solid form poses no special health risk."... 

TABLE 1. d -Polyimides prepared from perdeuterated dianhydrides and diamines and physical properties of the corresponding polymer. 

The polymers and copolymers described in this chapter were derived fi"om the novel anhydride-terminated disiloxane, 5,5 -bis(l,l,3,3-tetra-methyl-1,3-disiloxanediyl)norbornane-2,3-dicarboxylic anhydride (DiSiAn) (14). Both siloxane-polyimide polymers and copolymers based on DiSiAn and its polysiloxane derivatives were investigated. This chapter describes the synthesis, characterization, and physical properties of these materials. 

Measurements on Cured Polyimide. Table II below shows results obtained for the cured polyimide samples dissolved in concentrated sulfuric acid. For the samples cured in this laboratory, where the precursor polyamic acid M is known, the observed molecular weight of the cured polyimide is comparable. This suggests that the final physical properties of the cured polyimide should be determined by the molecular weight of the precursor polyamic acid formed. 

The physical properties of polypropylene, poly(ethylene terephthalate), and polyimide are greatly influenced by orientation of the polymer. Polypropylene and poly(ethylene terephthalate) become highly crystallized upon stretching. Oriented, crystalline poly(ethylene terephthalate), for example, has significantly higher modulus, tensile strength, and continuous use temperature than its extruded, unoriented analog (see Table II). 

Polymer Specimens. The materials used in this work were polyimide (PI),polyamide-imide (PAl), polyether-ether-ketone (PEEK), polyphenylene sulfide (PPS) and polyether sulphone (PES). The chemical formulas and physical properties of the specimen polymers are summarized in Table I. The specimen polymers, except PPS, were unfilled while the PPS specimen was filled with glass fiber of Uo wt. %. PAI and PES are amorphous polymer with considerably high glass temperature. The polymers, except PI, can flow at hi temperatures and allow the use of injection molding. 

Other physical properties of Vespel (SP-1 polyimide resin) ... 

Physical Properties of Cross-Linked Polyimide Membrane Sample Weight (%) Color... 

All of the highly aromatic polymers are resistant, relative to the nonaromatic polymers, to irradiation with either electron beam or y-rays. When irradiated in a vacuum many of these polymers are very stable and can show no change in physical properties even after high beam doses. For example, Kapton and Vespel aromatic polyimides have been shown to have resistance to both y-rays and electron beams up to doses of 100 MGy of irradiation [184]. In the presence of oxygen, the physical properties of the aromatic polymers can be dramatically changed. For example, an aromatic polysulfone showed no change in the flexural strength after irradiation with y-rays to 6 MGy, in vacuo. On the other hand, when the irradiation is carried out in the... 

ITO electrode and then flattened by a polymer film. For phase-only modulation, homogeneous LC alignment should be used. Thus, the polymer surface and the bottom ITO glass substrate with a thin polyimide alignment layer are rubbed in anti-parallel directions. The cell gap is controlled at 18 pm by Mylar spacers and hermetically sealed using ultraviolet-curable glue. To achieve a fast response time, a dual-frequency liquid crystal (DFLC) is used. The physical properties of the DFLC mixture are summarized as follows crossover frequency /<, 5 kHz, An 0.285 (at X=633nmand T=22°C), and dielectric anisotropy Ae = 4.73 at/= 1 kHz, and Ae = -3.93 at 50 kHz. 

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