Polyethylene high modulus fiber

Ultra-high modulus fibers such as aramid and carbon fibers have been currently utilized for composite material fabrication. Ultra-high modulus polyethylene (UHMPE) fiber is also applicable for composite fabrication because of the light weight in addition to its high modulus, vibration damping, and resistance to chemicals. However, this fiber has drawbacks such as poor interfacial adhesion with the polymer matrix of the composite because of highly hydrophobic nature of the fiber surface. 

Comparing the properties of conventional polymers and LCPs, the relations of structure properties can be clearly determined. Polyethylene is the best-known example of an isotropic polymer processable to high modulus fiber. 

Polyethylene can be made into a high-strength, high-modulus fiber (tradenamed Spectra by Allied Signal, Inc.) and then into a fabric. The polyethylene is an ultrahigh-molecular-weight polymer. The density of Spectra is the lowest of all fibers, which makes its use in aerospace laminates especially attractive. However, laminates must not be exposed to temperatures over 250°F. Spectra has very attractive electrical properties with low dielectric constant and loss factor. These properties are useful in radomes. Spectra is also used in ballistic applications like helmets and aircraft panels. 

Polyethylene (HOPE) occurs as a material with a modest modulus of elasticity or as a high modulus fiber, depending on its processing history but regardless of its chemical structure. 

Despite the absence of theoretical expressions, the practical apphcations of oriented crystallization have been developed and commercialized. The most important appUcation is in the synthesis of high-modulus fibers from conventional, flexible-chain, random-coil polymers such as polyethylene. In the process of solid-state extension (similar to the experiments of Southern and Porter), almost perfectly oriented, extended-chain structures are obtained by forcing a polymer billet through a tapered die. A major use of such fibers is in the reinforcement of composites. 

Biro. D.A.. Plcizeicr, G. and Deslandes, Y. (1993a). Application of the microbond technique. HI. Efl ecls of plasma treatment on the ultra-high modulus polyethylene fiber-epoxy interface, J. Mater. Sci. Lett. II, 698-710. 

Cho, C.R. and Jang, J. (1990). Adhesion of ultrasonic high modulus polyethylene fiber-epoxy composite interfaces. In Controlled Interphases in Composite Materials, Prod. ICCI-III, (H. Ishida ed.), Elsevier Sci. Pub., New York, pp. 97 107. 

Ladizesky. N.H. and Ward, I.M. (1989). The adhesion behaviour of high modulus polyethylene fibers following plasma and chemical treatments. J. Mater. Sci. 24, 27(>3- 27i. 

Ward, I.M. and Ladizesky, N.H. (1986). High modulus polyethylene fibers and their composites. In Proc. ICCI-I, Composite Interfaces (H. Ishida and J.L. Koenig, eds.), Elsevier, New York, pp. 37-46. 

In what follows, we first describe general processing techniques used to make synthetic polymeric fibers, followed by a description of the processing, structure, and properties of some important low modulus organic fibers. Finally, we describe, in some detail, two commercially important, high-stifihess fibers aramid and polyethylene. 

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