High-performance composites produced

Because of their unique blend of properties, composites reinforced with high performance carbon fibers find use in many structural applications. However, it is possible to produce carbon fibers with very different properties, depending on the precursor used and processing conditions employed. Commercially, continuous high performance carbon fibers currently are formed from two precursor fibers, polyacrylonitrile (PAN) and mesophase pitch. The PAN-based carbon fiber dominates the ultra-high strength, high temperature fiber market (and represents about 90% of the total carbon fiber production), while the mesophase pitch fibers can achieve stiffnesses and thermal conductivities unsurpassed by any other continuous fiber. This chapter compares the processes, structures, and properties of these two classes of fibers. 

Chemical Modification of Lignocellulosic Fibers To Produce High-Performance Composites... 

The last two decades of research on high performance rigid-rod polymers and molecular composites have produced a wide variety of material systems for evaluation. The purpose here is not to present a comprehensive review but rather to describe these relatively recent research developments with regard to the synthetic methods and approaches that have been utilized. In doing this some properties of the polymers are discussed as well as some of the problems encountered in conjunction with their synthesis and evaluation. In an effort to limit the scope of the review, we will address only aromatic heterocyclic rigid-rod polymers, extended chain polymers and derived molecular composites. 

A growing specialty application for acrylonitrile is in the manufacture of carbon fibres. These are produced by pyrolysis of oriented polyacrylonitrile fibres and are used to reinforce composites for high-performance applications in the aircraft, defence and aerospace industries. Other minor specialty applications of acrylonitrile are in the production of fatty amines, ion exchange resins and fatty amine amides used in cosmetics, adhesives, corrosion inhibitors and water-treatment resins (Brazdil, 1991). 

Dynamically formed membranes were pursued for many years for reverse osmosis because of their high water fluxes and relatively good salt rejection, especially with brackish water feeds. However, the membranes proved to be unstable and difficult to reproduce reliably and consistently. For these reasons, and because high-performance interfacial composite membranes were developed in the meantime, dynamically formed reverse osmosis membranes fell out of favor. A small application niche in high-temperature nanofiltration and ultrafiltration remains, and Rhone Poulenc continues their production. The principal application is poly(vinyl alcohol) recovery from hot wash water produced in textile dyeing operations. 

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