Aramide fibers sizing

Inhalation toxicology studies with fihrils made from p-aramid have been documented. Responses were detected, but the interpretation of these studies were regarded as controversial. There is some evidence for the biodegradabihty of p-aramid respirable-sized fiber-shaped particulates, which concept was supported in subsequent studies. Actually, material safety data sheets report the possibihty of lung injury, if fiber dust is inhaled for a prolonged time. On the other hand, aramids are not considered to be dangerous by skin contact or by ingestion. 

D. B. Warheit, K. L. Reed, J. D. Stonehuemer, A. J. Ohio, and T. R. Webb. Biodegradability of para-aramid respirable-sized fiber-shaped particulates (RFP) in human lung cells. Toxicol. Sci., 89 296-303, 2006. 

Aramid fibers are woven into fabrics for reinforcing polymers. The fabrics range in size from 2-mil (1 oz./yd. ) to thick 30-mil (6oz./yd. ) cloths. Kevlar is available in surfacing mats and cloth form. Surfacing mats can be had in weights of 0.4 and 1 oz./yd.. ... 

A combination of low density with a high strength and modulus of elasticity (Fig. 10.15) and high stability of the size in prolonged loading (Fig. 10.16) are characteristic of aramid fibers. The creep of Kevlar does not exceed the creep... 

The perfection, or absence of disorder, seen in the lattice fringes derived from equatorial reflections of aramid fibers is not found to be much different from the perfection of the meridional fringes. This may also be concluded from the lattice images of the PBT fibers. Apparently the broadening of the equator reflections in the X-ray diffraction pattern is mainly caused by the lateral crystallite size distribution. 

Figure 2 Graph shows the sizes of the transcrystalline zones formed around aramid fibers embedded in a Pebax matrix. The fibers have varying surface treatments...

The standard ASTM D2585 filament wound pressurized bottle test method utilizes a 0.15-m (5.75-in.)intemal diameter filament wound bottle as the test article. This standard test method (with variation in bottle sizes) has been used extensively by the rocket motor industry [47-50] to evaluate glass, aramid, and graphite fiber composite vessel performance. This test method has generally shown good results, but is a relatively expensive test method. Testing of one 0.5-m (20-in.) diameter bottle can cost up to 20K. Other disadvantages are ... 

Warheit DB, Harsky MA, Frame SR. 1996. Pulmonary effects in rats inhaling size-separated chrysotile asbestos fibers or />-aramid fibrils differences in cellular proliferative responses. Toxicol Lett 88 287-292. 

This periodicity of about 500 nm has been reported for banded textures observed in both the thermotropic copolyesters and the aramids [407, 430, 439-445]. The lateral banded textures exhibited by some of the thermotropes and the pleated sheet textures exhibited by some of the aramids are observed only in materials which have a poorer degree of molecular orientation. The more highly oriented thermotropic and lyotropic fibers do not exhibit these textures. For instance, heat treated Vectran fibers do not exhibit any lateral banding. Likewise, Kevlar 149 exhibits a higher tensile modulus than Kevlar 49 [448], nearly 80-90% of theoretical predicted values. This is consistent with increased crystallinity and crystallite size, and without a pleated sheet structure. The relationship of the optical... 

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