Polyethylene high modulus

An increase in rod-like arrangement of the macromolecules can also arise by stretching a polymer either in its solid state, either in the melt or even in solution (for polymers leading to lyotropic liquid crystals such as aromatic polyamides). This is the basis of the development of synthetic fibres including high modulus polyethylene Dyneema , polyamide Nylons and Kevlar , polyester Tergal or Dacron fibres. 

For the global advanced composites market, the average cost of high-performance fibre reinforcements (carbon, aramid, high modulus polyethylene, boron, R/S/T-glass and some E-glass) is estimated from 5.5 to 6 per kg. This moderate price is due to the decrease in the carbon fibre price. Some grades could fall to less than 10/kg in the short or medium term. 

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. 

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. 

Some polymers show large deviations. Polycarbonate (nr. 17) is an extremely tough polymer, with a high modulus polyethylene Id. (nr. 1) and poly(tetrafluoroethylene) (nr 8) combine a high impact strength with a low modulus. The other polymers are spread around the drawn line. 

Another effect of the high degree of chain alignment in these fibers is manifested when they are put in a polymeric matrix to form a fiber reinforced composite. High modulus polyethylene fibers such as Spectra or Dyneema are hard... 

High modulus polyethylenes have also been produced by the application of pressure to the polymer when it is molten under conditions of extrusion through a narrow capillary. It appears that in one case at least these methods differ in kind from those which involve stretching the molecules either in solution, or in the solid phase. 

The early studies of Capaccio and Ward >, which led to the discovery of high modulus polyethylene, were based on drawing low molecular weight polyethylene homopolymer at comparatively low temperatures. Subsequent investigations were addressed at three major extensions of this work ... 

It is only in the case of high modulus polyethylene produced by tensile drawing or hydrostatic extrusion that extensive structural studies have been undertaken. For these materials it was found in agreement with previous studies by Peterlin... 

Because of the potential applications of high modulus polyethylene for reinforcement of brittle matrices, it was soon recognized that the creep and recovery behaviour should be studied in some detail. 

As pointed out by Cansfield et al. the tensile behaviour of ultra high modulus polyethylene is very dependent on strain rate. A tensile strength of 1.5 GPa can therefore be obtained at high strain rates (similar to those adopted by Wu and Black) even for very low molecular weight polymers. 

The initial stimulus for the preparation of high modulus polyethylenes came from the recognition of the gap between the available stiffness and the theoretical stiffness. As indicated in this review the gap has now been largely bridged, which is emphasised still further by consideration of the total mechanical anisotropy as shown in Table 5. 

Solution processing also plays a vital role in the manufacture of high value, lyotropic high modulus fibres and also high modulus polyethylene fibres. In all these cases the additional cost and complication of solvent recovery is offset by the high value of the produced product. 

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