Ultrahigh modulus

Fig. 1. Specific strength and Young s modulus of various engineering materials where CF = carbon fiber HM/UHM = high modulus/ultrahigh modulus ...

Fibers produced from pitch precursors can be manufactured by heat treating isotropic pitch at 400 to 450°C in an inert environment to transform it into a hquid crystalline state. The pitch is then spun into fibers and allowed to thermoset at 300°C for short periods of time. The fibers are subsequendy carbonized and graphitized at temperatures similar to those used in the manufacture of PAN-based fibers. The isotropic pitch precursor has not proved attractive to industry. However, a process based on anisotropic mesophase pitch (30), in which commercial pitch is spun and polymerized to form the mesophase, which is then melt spun, stabilized in air at about 300°C, carbonized at 1300°C, and graphitized at 3000°C, produces ultrahigh modulus (UHM) carbon fibers. In this process tension is not requited in the stabilization and graphitization stages. 

L Steel J (ceramic fiber) Ultrahigh modulus carbon fiber... 

Aromatic poly(benzothiazole)s are thermally and thermooxidatively stable and have outstanding chemical resistance and third-order nonlinear optical susceptibility. Aromatic poly(benzothiazole)s can be spun into highly-oriented ultrahigh strength and ultrahigh modulus fibers. However, this type of polymer is insoluble in most organic solvents. Therefore, hexafluoroisopropylidene units are introduced in the polymer backbone to obtain soluble or processable aromatic poly(benzothiazole)s. 

Tissington, B., Pollard, G. and Ward, I.M. (1991). A study of the influence of fiber/resin adhesion on the mechanical behavior of ultrahigh modulus polyethylene fiber composites. J. Mater. Sci. 26, 82-92. 

Ultrahigh-modulus graphite-fiber-reinforced epoxy resin 303 7 0.25 0.006 6 1688 18.30 0.36... 

Celitntk> BASF Structural Materials (high-strength, high-modulus, and ultrahigh-modulus fibers]. 

Hence, the tremendously high equilibrium rigidity and the ordered structure of para aromatic polyamides favouring the formation of mesophases in the concentrated polymer solutions and permitting their use for the manufacture of ultrahigh-modulus fibers is ensured by both the frans-structure of the amide groups and the para position of the phenyl rings. 

In the meanwhile, the preparation and characterization of ultrahigh-modulus PE, PP, and POM has become a large field of interest. Contributions were made mairdy by Porter Ward ImaJa Nakayama and their coworkers. Bigg Ward , and... 

Fig. 10 Deformation methods to produce ultrahigh modulus materials.

Cifferi, A. Wards, I. M., Eds. "Ultrahigh Modulus Polymers" Applied Science, Barking, Essex, U. K., 1979. 

TPR thermoplastic rubber UHMPE ultrahigh modulus polyethylene... 

M. Kamezawa, K. Yamada, and M. TEtkayanagi, Preparation of ultrahigh modulus isotactic... 

We close this section with a few comments regarding the ultrahigh-modulus acrylic fibers. It is estimated that the theoretical crystalline modulus for polyethylene is 240 GPa hence there has been an intense effort over the last 10-15 years to develop spinning processes to exploit the high-modulus potential. This goal has been achieved by gel-spinning techniques [177]. Allen et al. [178] have estimated the theoretical modulus that might be obtained for... 

PAN by use of gel-spinning or other techniques to create a completely extended chain. Their estimate, based on a comparison of the rod-like PAN conformation with helical chain conformations of other polymers, is that the maximum tensile modulus of atactic PAN would be about 55 GPa. They conclude that PAN with ultrahigh modulus cannot be made by gel spinning, or by any other means, due to the intrinsic chain properties. It is proposed that the strong intramolecular nitrile repulsions that cause the PAN to adopt a rod-like, semiextended conformation do not allow the chain to unravel completely from its semiex-tended conformation. Attempts to develop gel-spinning processes in acrylic fibers are discussed in Section 12.5.4. 

HM high modulus, UHM ultrahigh modulus, HS high-strength, I made from isotropic liquid [81]... 

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