Polyimides composites

Tests of a graphite-reinforced polyimide composite (C6000/PMR15) did not show any effect of radiation exposure (1 MEV electrons 6x109 rad total dose) on the thermal expansion behavior (14). DMA curves for unirradiated and irradiated composites were essentially identical over the temperature range of the thermal expansion measurements. 

Chen, E.J.H. and Croman R.B. (1993). Microdebonding investigation on the effects of thermal residual stress on the bond strength of a graphite/polyimide composites. Composites Sci. Technol. 48, 173-179. 

Z. Ounaies, C. Park, K.E. Wise, E.J. Siochi, and J.S. Harrison, Electrical properties of single wall carbon nanotube reinforced polyimide composites, Compos. Sci Technol., 63(11) 1637-1646, August 2003. 

The author notes many interesting avenues of future research that could be carried out to see if the potential for epoxy-polyimide composites can be realized and the physical phenomena that they exhibit could be explained. 

Gibbs HH (1996) Hydrothermal effects in polyimide composites. In Abadie MJM, Sillion B (eds) Polyimides and high performance polymers (Proceedings of the 4th European Technical Symposium on Polyimides and High Performance Polymers, STEPI4). Montpellier-2 University Press, Montpellier, p 306... 

Fig. II. The ultimate (lcxural strength at 4.2 K as a function of the absorbed dose in matrix for various polymer composites. (G) TGDDM/DDS (tetraglycidyldiaminodiphenylmethane cured with diaminodiphenylsulfone) ( ) DGEBA/DDM (diglycidyl ether of bisphenol A cured with dia-minodiphenylmethane) (C>) G-10CR (FI) G-l ICR ( ) polyimide composite...

TABLE 1. Optical alignment of polyimide compositions derived from 1,2,3,4-cyclobntane-tetracarboxylic dianhydride and selected diamines. 

Blended polyimide composites containing 11% neutral dithiolene nickel(II) derivatives were selective for propene in propene/propane stream feeds. Evidence of propene absorption was indicated by a color change of the composite. The selectivity ratio was between about 1.1 and 2.0. 

Neutral and ionic dithiolene derivatives that were prepared and used in polyimide composites are provided in Tables 1 and 2, respectively. 

TABLE 1. Neutral dithiolene derivatives blended in polyimide composites. 

TABLE 2. Ionic dithiolene derivatives nsed in polyimide composite blends. 

Betts, S., Dackow, J. and Murray, S.F., Performance Characteristics of Self-Lubricating Polyimide Composites, Proc. 2nd ASLE Inti. Conf. on Solid Lubrication, Denver, Colorado, (15-18 Aug. 1978), ASLE SP-6, p. 195. 

SCHEME 29. Eormation of phenol-formaldehyde/polyimide composite materials... 

PADS containing siloxane polyimide compositions were evaluated for adhesion to silicon wafers according to the identical test protocol employed by Davis (7). As shown in Table VIII, these polymers had adhesive properties similar to the GAP derived siloxane polyimides however, the PADS containing materials are of higher thermostability than the GAP derived materials. Thus, the PADS class of materials offers a balance of adhesive and thermal qualities not hitherto attainable. 

Graphite Fiber Reinforced TSTR Polyimide Composites (3). 

The flexural strengths (three-point method) of these two unidirectional HMS graphite fiber reinforced TSTR polyimide composites with or without post curing were measured with a universal Instron machine at room temperature and at 316°C. These results are shown in Table II. 

Figure 4. Exposure of triaryl-s-triazme ring polyimide composite to a bunsen burner flame (1100-1250°C).

Figure 5. Bunsen burner burning test of graphite fiber reinforced polyimide composites. Key a, TSTR-XL-PI/GrF specimen before test b, TSTR-XL-PI/GrF specimen after test and c, PMR-15-PI/GrF specimen after test.

Strathmann prepared an all-polyimide composite membrane-both bottom and top layers.97 A microporous asymmetric film of the polyamic acid intermediate was cast by quenching in acetone, then dried and thermally cyclized to the polyimide at 300°C. The microporous polyimide sheet was then overcoated with a dilute solution of the same polymer, which was allowed to evaporate to give a 300-angstrom-thick coating. This was also cyclized to the polyimide to generate a fully solvent resistant reverse osmosis membrane. 

Asymmetric membranes are made from solution in the form of a hollow fiber, but the process used to form a thin, pore free dense layer on these hollow fibers is not disclosed.45 46 However, US patent 4,440,64312 describes a unique process for producing pore-free polyimide composite membranes. An asymmetric polyimide porous substrate is prepared from solution. When fully imi-dized, the substrate is insoluble. The substrate can now be coated with a poly-amic acid from dilute solution (— 1 %). When fully imidized, the resultant polyimide coating becomes the separating layer. This process allows use of the same or different polyimides for the substrate and the separating membrane. While the examples in the reference describe preparation of flat sheet membranes, this process could be used to prepare hollow fiber membranes. 

Aeronautics and Space Administration space shuttle program. However, the high glass transition temperatures of polyimides make processing difficult. Thus, the acid and amine monomers often are polymerized in solution to form a poly(amic-acid) resin. This polyimide precursor resin solution may be applied then to a fiber backing and cured at 200-300°C to form a thermally stable polyimide composite. 

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