Polyimides polymer-matrix composites

Keywords ceramic thin films, titania, polyimides, polymer matrix composites 1. Introduction... 

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. 

Fig. 21. Dynamic thermal stability [121] of a variety of polymeric electro-optic materials. All materials involve the Disperse Red chromophore. Trace 1 PMMA composite material trace 2 chromophore covalently attached by one end to a soft (PMMA-like) matrix [138] trace 3 DEC chromophore with both ends attached to a soft polymer matrix [138] trace 4 Disperse Red chromophore covalently attached at one end to a polyimide polymer matrix [121] trace 5 DEC-type chromophore with both ends attached to a sol-gel type matrix [139]...

A large number of studies have been made on a of polymer matrix composites of epoxy, polyimide and other polymers reinforced with carbon and Kevlar fibers [117-123]. The carbon and graphite fibers are characterized by slightly negative (Xi in their axial directions and very large positive aj in their radial directions [122-124]. The unidirectional and bidirectional composites based on them are found to demonstrate highly anisotropic thermal expansion behavior. In unidirectional composites,... 

Politi, R.E., Recent developments in polyimide and bismaleimide adhesives in T.T. Serafini (Ed.), High Temperature Polymer Matrix Composites (pp. 123-134). Noyes Data Corporation, 1987. 

Currendy, epoxy resins (qv) constitute over 90% of the matrix resin material used in advanced composites. The total usage of advanced composites is expected to grow to around 45,500 t by the year 2000, with the total resin usage around 18,000 t in 2000. Epoxy resins are expected to stiH constitute about 80% of the total matrix-resin-systems market in 2000. The largest share of the remaining market will be divided between bismaleimides and polyimide systems (12 to 15%) and what are classified as other polymers, including thermoplastics and thermoset resins other than epoxies, bismaleimides, cyanate esters, and polyimide systems (see Composites,polymer-matrix-thermoplastics). 

Aerosol spray delivery, 23 196 Aerosol sprays, 7 773-774 Aerospace applications aluminum alloys, 2 340 artificial graphite in, 72 740-741 for high performance fibers, 13 397-398 of liquid-crystal polymers, 20 85 metal-matrix composites in, 16 191 polyimide matrix composites in, 20 284 Aerospace bearings, corrosion resistance of, 74 452... 

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 fibres are surface treated during manufacture to prepare adhesion with the polymer matrix, whether thermosetting (epoxy, polyester, phenoUc and polyimide resins) or thermoplastic (polypropylene. Nylon 6.6, PMMA, PEEK). The fibre surface is roughened by chemical etching and then coated with an appropriate size to aid bonding to the specified matrix. Whereas composite tensile strength is primarily a function of fibre... 

Table 1 contains the elemental compositional results obtained by ESCA for Cu coated polyimide films before and after T H exposure. As shown, the metal diffuses into the polymer matrix after the T H exposure. The same result was obtained for Ni. The diffusion of Cu into PI-5878 surfaces detected in our ESCA results correlates with the 4X increase in peel strength (after 500 hours at T H - 85 C 80%) measured (4) for thick Cu films deposited onto cured PI-5878... 

Polyimide characterised by thermal and thermal-oxidative stability at elevated temperatures, chemical resistance and good mechanical properties is relatively new in the family of polymer foams [3]. In some cases, depending on the nses, additional reinforcement can be inclnded. Examples are fibre reinforced foams and syntactic foams which are composites containing hollow glass, ceramic or plastic micro-spheres dispersed throughout the polymer matrix. 

Matrix Materials Polymers used for matrix materials are usually thermosets, with epoxies being the most common (35). Others are polyesters and phenolics. Sometimes thermoplastics are used, principally polyimides, polysulfones, and polyetheretherketone (PEEK). The matrix has several roles in polymer-fiber composites. These include maintaining desired fiber spacing, transmitting shear loads between layers of fiber, and reducing the tendency to transmit stress concentration from broken fibers to intact fibers. 

The presence of reinforcanent in polymer (nano)composites (Thomas et al. 2011 Wen 2007) generally increases the value of E modulus due to restrictions of vibrations and short-range rotational motions (Bindu and Thomas 2013 Dufresne 2000 Liu et al. 2005 Musto 2006). Exceptions to this behavior exist, and one of them was reported on the EeS2/polyimide composite (Sava 2009). Incorporation of low quantities of pyrite microparticles restrains the possible physical interactions among polyimide chains, decreasing the rigidity of the composite relative to the pristine polyimide. Another situation was mentioned for an all-polymer composite obtained from a pair of incompatible polymers polysulfone (PSF) (the matrix polymer) and cross linked polydimethylsiloxane (PDMS) submicron particles (the disperse phase) (Racles et al. 2013). All-polymer composites contain polymer nanoparticles as the disperse phase in a polymer matrix and, from the point of view of properties, these are situated between polymer blends and polymer composites. The PDMS particles act like a plasticizer for the PSF matrix (E p p = 2 GPa, E psp/pp,Ms = 0.7 GPa). 

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