POLYETHYLENES
Certran®
Hoechst Celanese produces this polyethylene fiber as a lower modulus version of Spectra. It has similar properties to Spectra including superior resistance to flex fatigue and UV degradation and a tendency to creep (permanently and continuously stretch under a sustained load).
Dyneema®
Equivalent to Spectra®, Dyneema® is produced by the Dutch company DSM. It is often used by European sailcloth manufacturers, is available in a wider variety of yarn sizes than Spectra, and is growing in popularity in North America.
PEN Fiber (polyethylene naphthalate, Pentex®)
A modified polyester fiber made my Honeywell, Pentex has 2.5 times less stretch than standard polyester fibers (between polyester and Kevlar 29). Because it does not shrink as much as a good Dacron fiber (5% vs. 15%), Pentex weaves cannot be as tight as a Dacron weave. Thus, woven Pentex must be highly resinated and requires great care to retain the shape and extend the life of a sail. Pentex is much better suited to laminated sailcloth, in which the fibers are laid straight for strength and are sandwiched between sheets of film for stability. Pentex laminates are a lower-cost option for the racing sailor who is looking for a slightly higher performance sail but does not want to spend the money for a Kevlar or other exotic-fiber sail.
Spectra®
Spectra® is a highly processed ultra high molecular weight polyethylene (UHMWPE) made by Honeywell. Spectra offers good UV resistance (on par with polyester), very high initial modulus numbers (second only to high modulus Carbon Fiber), superior breaking strength, and high flex strength. More careful testing, however, reveals that it also exhibits a property known as “creep” (permanent, continuous elongation under a sustained load) that results in a change in shape as the sail ages. Creep makes Spectra unfit for high performance racing applications and more suited for large cruising boats where strength, UV resistance, light weight and durability are paramount. Spectra yarns are white, but by dying other laminate elements, it has been offered in additional colors, particularly light blue.
