Aramid fibers surface chemistry

The value of the epoxy resins lies in their reactivity with a variety of chemical groups. This enhanced reactivity also means that the surface chemistry of the reinforcement which the epoxies are cured against, can alter the local structure in the interphase regionJl). The most common reinforcement surfaces cured in contact with the epoxies are carbon/graphite fibers, glass fibers, aramid fibers and metal oxides. The surface chemistry of these reinforcement surfaces is quite diverse and in many cases can be the reason for alteration of the interphase epoxy structure as compared to the bulk. 

New fibers are being proposed all the time. During the 1980s, the aramid fibers, including Kevlar and Nomex, along with other nylon derivatives, enjoyed a brief spell of popularity. Eventually their hydroscopic nature and markedly positive Poisson s ratio, along with poor surface chemistry modifications, rendered them less suitable than carbon fiber for aerospace applications. 

Although the flat membranes and disks afford good separations, their aspect ratio requires specifically designed cartridges with sophisticated distributors of the mobile phase all across the surface of the disk. In contrast, tubular devices such as columns do not need these distributors because the top part of the bed itself serves this purpose and their construction is much simpler. This led Ladish to the fabrication of stationary phases from rolled flat materials—woven textile fabric [95]. The cylindrical roll is then inserted into typical HPLC column. The number of chemistries is limited only by the variety of fibers. Aramid columns behave as a hydrophobic interaction phase [95] and cotton fabrics transformed to an ion-exchange derivative can be used in lEC [96]. Ladish et al. [97] published a... 

---