Fluorocarbon line Some modern monofilament lines are made from
polyvinylidene fluoride (PVDF), a
fluoropolymer often marketed as
fluorocarbon. Fluorocarbon lines or "fluoro lines" are valued for their similar
refractive index to that of
water, making it less visible to
fish, which may not swallow the bait if it sees the line. Fluorocarbon lines have greater surface
hardness than nylon lines and are more
abrasion-resistant against underwater rocks and
snags, yet are more
shock-resilient than
braided lines when fighting fish, thus making them ideal to use as
leader lines especially when the mainline is braided. They also have less
memory,
stretch and
moisture expansion than nylon lines, making it easier to keep the line taut and transmit vibrations, which is essential in
lure fishing where the angler is very reliant on tactile sensitivity. PVDF is also a denser material and therefore not nearly as
buoyant as nylon monofilament, and anglers often utilize fluorocarbon lines when they need lighter baits/lures to sink more quickly and stay deeper below the surface without using heavy
sinkers.
Copolymer line A newer type of modern monofilament lines are
composite lines that are fused from at least two different
substrates via a process known as
copolymerization. Most copolymer lines are nylon-based
polymer blends fusing a blend of nylon with another higher-density one, although recently "tripolymer" lines that fuse three different blends of nylon have also appeared on the market. Compared to conventional single-blend ("plain") monofilament lines, copolymer lines have much higher test weight (
strength) especially for small diameters, have less stretch, and are more abrasion-resistant. They are stronger than fluorocarbon lines per diameter but also less rigid, which makes them more shock-resilient and
knot-friendly, although also more susceptible to wind-knotting (random entanglement of loose line loops). Like plain monofilament lines, copolymer lines tend to sink slowly in water, and are better suited for
lure fishing near the surface (e.g.
dry fly fishing). Some copolymer lines are additionally coated with
fluoropolymer (
trademarked as "FluoroKote") to give more fluorocarbon-like surface property and to change the refractive index, as well as to also allow faster sinking as the added fluoropolymers are generally denser than nylon. ==Use==