M-Aramids

A p-aramid polymer supporting a catalyst agent has been presented for several reactions. The composition exhibits an improved catalytic activity in comparison to m-aramid polymer catalyst support. The actual catalyst agent is adhered on or within the support. 

Various nonwoven structures have been developed as well. The least important among sheet structures are films. There are two film products (see Section 13.3) based onp-aramids and none on m-aramids. The significant cost differential is the most likely reason for this situation. On the other hand a very large market has been developed for papers based on both p-aramids and m-aramids. In general, these papers are based on short fibers (floe) and a binder (fibrids), but other components have been explored as well. A very small market exists for particles other than fibrids and pulps. 

The basic development and the first commercial introduction of these materials were done by DuPont, which continues to be the largest producer. m-Aramid fiber products (staple. 

Typical properties of commercial aramid fibers are given in Table 13.4. While yarns of m-aramids have tensile properties that are no greater than those of aliphatic polyamides, they do retain useful mechanical properties at significantly higher temperatures. The high glass... 

As we have mentioned earlier, m-aramid papers are produced exclusively by DuPont and thus most of the application data are based on Nomex papers. 

In the form of paper or pressboards, m-aramids provide an optimum balance of properties for use as electrical insulation in transformers, motor, generators, and other electrical equipment. Properly used, these materials can extend the life of an electrical equipment, reduce the frequency of premature failures, and protect against random electrical stress situations. 

Tags and labels of m-aramid paper for in-process bar coding are used where high temperature stability and chemical resistance are required. In loudspeakers, m-aramid sheets are used for voice coil insulation and for the speaker cone itself. Bus bars in lithium ion batteries for portable telephones and computers are insulated with m-aramid paper. Photocopiers and laser printers that operate at high temperatures use cleaning rollers and webs made from m-aramid paper. 

As m-aramid fibers are best known for their flame resistance, p-aramid fibers are universally recognized as the material of choice for ballistic protection. While p-aramids do play a critical role in this application we will attempt to show that their unusual properties are also suitable for a wide variety of other end-uses. 

Because of their superior compression, shear, and fatigue properties, structures based on p-aramid cores allow even greater weight reduction than incumbent w-aramid cores. Recent commercial adoptions include flooring panels in weight critical programs such as the extended Airbus A-340 and the double deck Airbus A-380. p-Aramid cores have also replaced m-aramid cores in the elevators and rudders of these aircrafts [121,124], because of their superior hot-wet characteristics. 

Zylon HM Zylon AS P- Aramide m- Aramide Steel fibers Carbon fibers PBl Poly- estea ... 

Scanning electron microscope images show that the carbon nanotubes are well dispersed in the composite films and are wrapped with m-aramid chains [27]. Further, the interfacial thickness of the aramid wrapped carbon nanotubes decreases with their content. 

Similarly, a poly(acrylonitrile)/m-Aramid hybrid composite exhibits a 7 log reduction against E. coli andS. aureus [111]. Also, m-Aramid/chitosan hybrid films are antimicrobial [112]. 

Jeong YG, Jeon GW. Microstructure and performance of multiwalled carbon nanotube/ m-aramid composite films as electric heating elements. ACS Appl Mater Interface 2013 5(14) 6527-34. 

Jeon GW, Jeong YG. Electric heating films based on m-aramid nanocomposites containing hybrid fillers of graphene and carbon nanotube. J Mater Sci 2013 48(ll) 4041-9. 

Kim SS, Kim M, Lee J. Cellulose filter coated with m-aramid for water disinfection. J Appl Polym Sci 2013 129(6) 3454-8. 

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