Examples of industrial fiber composites are double braids with nylon or polyolefin cores covered by abrasion and UV resistant polyester braided covers, and single braids where yarns from two fibers are combined in each strand – polyester and polypropylene are often used together in this way. A third method is use of a ‘copolymer’ fiber.
In this method, a polyolefin polymer is combined with, typically, a polyester polymer to produce a fiber with a new set of properties.
In many cases, the goal of the textile engineer is for the cover and the core of a double braided product to break at the same time. In others, the purpose of the cover is to protect a load bearing core from damage. This is often the case with kernmantle products used for climbing and rescue.
The construction used also has a good deal to do with the properties of the finished line. The way a given fiber behaves as a rope component can vary greatly. For instance, a rope with an un-braided parallel polyester core will tend to have less stretch than one with a braided polyester core (there may be a downside of reduced flexibility here).
Combining high performance fibers – UHMWPE (Spectra, Dyneema)yarn may be combined with aramid or polyester yarn in stranding, or used a core covered with a braided polyester or multifilament polypropylene cover – opens up a whole new menu of possibilities. For use as a cable pulling rope, it is sometimes braided without being combined with other fibers – it’s extremely strong, with low stretch, and a naturally slippery surface – but is, as are most high performance fibers, pretty expensive.
UHMWPE is also used in round slings, serving as the core while a tubular nylon or polyester webbing serves as the cover. These slings are used by rigging contractors to make huge lifts in places like utility plants and steel mills.
Aramids – like Kevlar, Technora, and Nomex, are not as strong as UHMWPE fibers, but many are three times stronger than nylon, and have very good heat resistance. Nomex has especially good resistance to high temperatures.
Liquid Chrystal Polymer – Vectran is another super-strong fiber, sometimes used alone in slings, sometimes covered with polyester. Vectran was used to produce a “Smart Rope” in research with a goal of making rope that can self-monitor loading and alert users in order to prevent reaching the point of failure.