Poly p-phenylene terephtalamide

An analogous case, of identical chain conformations as well as of similar unit cell dimensions, have been described for the two crystalline forms of poly-p-phenylene terephtalamide [33-36] (better known with the trade name of Kevlar). The projections along the c axis of the packing of the chains proposed for the two forms [36] has been sketched in Fig. 8, corresponding to the localization of the chain axes in (0,0, z) and (1/2,1/2, z) for the more common polymorph, in (0, 0, z) and (1/2,0, z) for the other polymorph. 

PPTA PS poly(p-phenylene terephtalamide) polystyrene V volume fraction of interface... 

Aramid is sensitive to UV light. The effects of simulated solar UV irradiation on the mechanical and structural properties of a poly(p-phenylene terephtalamide fiber have been studied." UV irradiation deteriorates the surface and defect areas of the fiber by photoinduced chain scission. 

Tsou et al. (1996) prepared molecular composites by dispersing rigid-rod molecules of ioiucally-modified poly(p-phenylene terephtalamide) in a polar poly (4-vinyl pyridine) (PVP) matrix. The mechanical properties of the molecular composite were found to increase with concentratimi and to attain maximum values at about 5 wt% of the PPTA anion. When specific interactions are not present, as in composites with nmi-anionic PPTA, the properties are significantly reduced compared to those of the PPTA anion/PVP composites. 

According to the US Federal Trade Commission (FCT), wholly aromatic PAs are synthetic PAs in which at least 85% of amide groups are bound directly to two aromatic rings [1]. Aromatic PAs were first introduced in commercial applications in the early 1960s by DuPont under the tradename Nomex . It is used extensively in the production of protective apparel, air filtration, thermal and electrical insulation as well as a substitute for asbestos. Later para-aramid called Kevlai was introduced in also market by DuPont in 1973. The chemical structure of the poly(p-phenylene terephtalamides) (PPPT) and the poly(m-phenylene isophtalamides) (PMPI), which are commercial aramids of great economic relevance are shown in Figure 5.1. 

Poly(p-phenylene terephtalamides) (PPPT) Poly(m-phenylene isophtalamides) (PMPI)... 

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