Nomex Poly

As mentioned earlier, amides are less reactive than esters, and diamides are even less reactive. An example of this trend is the low reactivity of the dibenzoyl amides of 1,3- and 1,4-diaminobenzene, which are model compounds for the polymers Nomex [poly(l,3-phenylene isophthalamide)] and Kevlar B [poly (1,4-phenylene terephthalamide)] [243]. 

Aromatic polyamides or aramids. The best known in the specialty fiber market are Nomex (poly-m-phenyleneisophthalamide) and Kevlar (poly-p-phenyleneterephthala-mide). 

Nomex Poly(m-phenyleneisophthalamide) fibers, PPA E. I. du Pont de Nemours... 

Aliphatic polyamides, also known under the generic name nylon. Industrial nylons with the general structure [-RNHCO-] , such as PA-6, PA-11, and PA-12, are called monadic those with the general structure [-NHRiNHCOR2CO-] are called dyadic (PA-4,6, PA-6,6, PA-6,9, PA-6,10, and PA-6,12). Aromatic polyamides or aramids. The best known in the specialty fiber market are Nomex (poly-m-... 

Poly( j-phenylene isophthalamide) (structure 4.59), sold under the trade name Nomex, exhibits good thermal stability decomposing above 370°C. It is used in flame-resistant clothing. It is also used in the form of thin pads to protect sintered silica-fiber mats from stress and vibrations during the flight of the space shuttle ... 

The first commercial aramid fiber was based on poly(m-phenylene isophtha-lamide) and has the trade name Nomex (Du Pont) [26-29] ... 

Filters can be grouped on the basis of different characteristics. For example, they can be grouped on the basis of the design capacity of the filters according to the particle concentration or loading [Svarovsky, 1981] or they can be grouped on the basis of the materials of the filters, e.g., fabric or nonfabric [Cooper and Freeman, 1982], Most filters in use are bag filters, which are fabric. The common fabric materials include cotton, polyester, wool, asbestos, glass, acrylic, polytetrafluoroethylene (Teflon), poly (m-phenylene isophthalate) (Nomex), polycaprolactam (Nylon), and polypropylene. 

Mw of 73 000 (Scheme 55) [229]. Colquhoun and coworkers also reported a ring-chain interconversion system in poly(m-phenylene isophthalamide) (Nomex) [230]. Cyclodepolymerization was best achieved by treating a solution of the polymer in DMSO containing CaCl2 or IiCl as a solubilizing... 

Besides scientific names, many polymers are indicated by their common name, trade name, brand name, or abbreviation (commercial names) [4]. Typical examples of common names are nylon or silicone. Several nylons are known and the name nylon 6 is used for poly[imino(1-oxo-1,6-hexandiyl)], the name nylon 66 is used for poly(iminohexa-methyleneiminoadipolyl), etc. Trade names such as Teflon for poly(tetrafluoro-ethylene) made by DuPont, Nomex for poly(iminoisophthaloylimino-1,3-phenylene), or Kevlar for poly(iminoisophthaloylimino-1,4-phenylene) are also common. Many abbreviations are in use for both homopolymers and copolymers. Table 1.2.1 gives some of the common abbreviations for polymers. 

Besides the aliphatic and aliphatic/aromatic nylons, aromatic polyamides have excellent capability to form fibers. Among aromatic polyamides the most common are Kevlar or poly(imino-1,4-phenyleneiminocarbonyl-1,4-phenylenecarbonyl) or poly(phenylene terephthalimide), and Nomex or poly(phenylene isophthalimide). These compounds are included in a group of polyamides known as aramids. The structures of Kevlar and Nomex are shown below ... 

The Py-GC/MS results for a poly(phenylene isophthalimide) or Nomex sample are shown in Figure 13.3.9. The pyrolysis was done at 850° C in He, with the rest of the conditions similar to those used for other examples previously discussed (see Table 4.2.2). Higher temperature was necessary for the sample since Nomex decomposes more slowly at temperatures used, for example, for the pyrolysis of aliphatic nylons. 

Figure 13.3.9. Result for a Py-GC/MS analysis for poly(phenylene isophthalimide) or Nomex . Pyrolysis done on 0.4 mg material at 85(f C in He, with the separation on a Carbowax type column.

A number of polyamide copolymers are known to have practical uses. The copolymers include those with different amides such as poly(caprolactam-co-laurolactam), poly(2,2,4-trimethyl-1,6-hexandiamine-co-2,4,4-trimethyl-1,6-hexandiamnie-co-1,4-benzendicarboxylic acid), poly(s-caprolactam-co-hexamethylene diamine-co-terephthalic acid), poly(hexamethylenediamine-co-terephthalic acid-co-isophthalic acid), etc. The addition of longer alkyl chains in an aromatic polymeric amide may improve some mechanical properties, but thermal resilience is in general reduced. For example, poly(hexamethylenediamine-co-m-xylylenediamine-co-isophthalic acid-co-terephthalic acid) starts decomposing at about 310° C, significantly lower than Nomex , for example. The same decrease in the decomposition temperature is seen for other mixed copolymers such as nylon 12 copolymers that include cycloaliphatic and aromatic segments. 

About half of the benzene produced as a chemical feedstock is for styrene production, followed by large fractions for phenol and cyclohexane-based products. As much as half of the toluene produced is converted to benzene, depending on the price and demand differential. The largest use of toluene itself is as a component of gasoline. Much smaller amounts are used as a solvent, or in the manufacture of dinitrotoluene and trinitrotoluene for military applications. Xylenes are also used in gasoline formulations and function as octane improvers like toluene. para-Xylene and o-xylene are the dominant isomers of value as chemical feedstocks, for the production of terephthalic acid (and dimethyl terephthalate) and phthalic anhydride, respectively. Polyester and the synthetic resin markets, in turn, are major consumers of these products. meto-Xylene is oxidized on a much smaller scale to produce isophthalic acid, of value in the polyurethane and Nomex aramid (poly(m-phenylene isophthalamide)) technologies. 

Nomex aramid, made from m-phenylenediamine and isophthaloyl chloride, produces poly(m-phenylene isophthalamide) with a melting point of 380-390°C, and substantially avoided the problems of high-monomer cost (Eq. 21.17) [23]. 

Nylon 6T melts at 370 C, Nomex is practically flameproof. Kevlar, poly (p-phynyleneterephthalamide) represents a break-through in high modulus aromatic polyamide fibre and mainly used as reinforcement tyres, conveyers belt etc., PBI is... 

Nylons prepared from aromatic diamines and diacids (aramids) can lead to very high-heat amorphous nylons such as Du Font s Nomex materials [poly(m-phenyleneisophthalamide)], or the highly oriented crystalline Kevlar fibers [poly(p-phenyleneterephthalamide)] derived from liquid-crystalline technology. Both of these aramids are sold as fibers. They have excellent inherent flame-retardant properties, and Kevlar exhibits a very high modulus. 

Liquid crystal aromatic polyamides (PARA), poly(meia-phenylene isophthalamide), Nomex , and poly(para-phenylene terephthalamide), Kevlar -49, were commercialized in 1961 and 1965, respectively. Amorphous aromatic polyamide, Trogamid , was introduced in 1969, and polyphthalamide Amodel in 1991. 

---