Polyethylene ballistic properties

The ballistic properties of high performance fibers such as ultra high molecular weight polyethylene (UHMWPE) and aramid and their composites are very well known. The ballistic properties of flax, hemp, and jute fabric reinforced PP composites processed by hot compression molding have also been investigated. It has been shown that flax composites exhibited better properties when compared with hemp and jute composites [48]. 

Dyneema UD is a unidirectional laminate made of two layers of extended chain polyethylene filament tows, cross plied and sandwiched in a thermoplastic film. It is one of the strongesf " and most exclusive fibre laminates designed for ballistic protection. It is very thin and one of the lightest ballistic protection materials available, with a relative density lower than that of water. - It offers good protection from cuts and slashes and will also help to protect against stabs. It will withstand temperatures of up to 140 °C and maintains its protective properties down to -150 °C (Fig. 7.15). 

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. 

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