Silica: Big Deal About a Small Thing

Silica: Big Deal About a Small Thing

St. Croix's dynamic analyzer tests rod blank strength. According to Jason Brunner, director of engineering, most rods with Matrix Resin withstand more than 100 foot-pounds of torque at the handle. Photo: Courtesy of St. Croix

The biggest improvement to fly rods in 2011 is likely attributable to tiny round silica particles less than a nanometer — one billionth of a meter — in diameter. You'd need a powerful electron microscope to see a single one of these minute spheres, and if you gathered half a pound of them, you'd see a fine white powder that would dissipate in the slightest breeze.

Silica (silicon dioxide) is the most abundant mineral in the Earth's crust and has been used in useful technologies such as glass, fiber optics, microelectronics, and now fly rods. 3M — the same company that makes a silica sandpaper used to polish diamonds, and annually sells about $2 billion worth of other products as diverse as adhesives and insect repellents — also makes Matrix Resin, a viscous synthetic liquid containing 3M's proprietary nano-silica filler.

According to 3M, when Matrix Resin is cured, or hardened, together with carbon fiber to produce golf club shafts or fishing rods, the composite structure is harder and more durable, has greater shear and compression strength, and greater resistance to fracturing than other companies' resins. Sound like a sales pitch for engineers? That's because it is. It's exactly the sales pitch that 3M gave to fly rod manufacturers when the company invited them to test its new resin.

One engineer/fly rod designer I spoke with said he first used the 3M resin in a few sample blanks, and subjected them to a gauntlet of compression and fracture tests.

"I called 3M back right away and told them we wanted an exclusive on this stuff," he told me. "But they told me they have to sell this to everyone." According to Jason Brunner, director of engineering for St. Croix, the resin is also 23 percent more expensive than the company's previous system.

How it Works

How can microscopic spheres of silica make a fly rod stronger? Carbon fibers alone have little strength, let alone stiffness. The resin, bonded with the carbon fibers and then cured with heat, is what makes the composite hold its tubular shape and resist compression.

The past decade, manufacturers have focused on using higher-modulus graphite, using graphite scrim instead of fiberglass, and aligning the graphite fibers more accurately — all in hopes of saving weight and improving performance. Fly rod resin systems received relatively little attention from most manufacturers until 2008, when Orvis switched from a traditional epoxy resin to a stronger and lighter thermoplastic resin in its Helios rods — and shot the lights out in consumer popularity. According to Chief Executive Leigh (Perk) Perkins Jr., Orvis sold 10,000 of the $750 rods in that recession year, making it the company's best-selling product, and one of the most noteworthy fly rods in recent history.

Matrix Resin is also cured with heat, but owes its strength to the nano-silica particles in the compound. Just as concrete becomes stronger and more durable with rebar and gravel in the mix, the cured resin and carbon fiber composite is stronger with the silica particles because they bond the carbon fibers together better by filling all the microscopic empty spaces between the fibers. Larger filler particles cannot enter such tiny spaces.

Continued - click on page link below.

This image from an electron microscope shows individual carbon fibers (the large circles) and nano-size silica filler in the resin between the fibers. According to 3M, these tiny particles make carbon fiber composites up to 30 percent stronger. Photo: Courtesy of 3M

Stronger Not Always Better

A nearly unbreakable golf club or fishing rod is not a new development. Berkley's Ugly Stik is tough to snap, but that doesn't mean you'd want to fly cast with it. Certainly a broken rod is an annoyance, and consumers appreciate having a rod that doesn't snap at the first nick of a Clouser Minnow, but toughness is just one concern of most rod manufacturers.

For most designers, the Holy Grail has always been to make a better-casting rod: one that is lighter, tracks true along a straight plane, recovers quickly from a loaded to a straight position, and comes to a dead stop at the end of the stroke with minimal secondary vibrations.

These are the same performance parameters that have driven rod builders for 200 years, and caused fly fishers to switch from solid greenheart rods to bamboo to fiberglass and finally to graphite (carbon fiber). At each step, the new material gave fly fishers rods that were less cumbersome, more efficient, and more responsive.

With a stronger resin and a stronger carbon/resin composite, manufacturers have the option to use less resin and less carbon fiber to produce a rod that is equally strong but much lighter, or much stronger at the same weight, or somewhere in between.

At the time of publication, three companies are already using Matrix Resin in their manufacturing processes, and others are at various stages in the development process.

St. Croix is using the resin in its popular high-performance Legend Elite fly rods, as well as in the new Bank Robber rods, co-developed by streamer guru Kelly Galloup. The new rods are 6- and 7-weight, 9-foot rods for big-river drift-boat fishing and "pounding the banks."

Legend Elite rods have the same design, same tapers, same weight, and same price as always, but according the St. Croix, the new Legend Elite series is 30 percent stronger compared to previous Elites.

Bank Robber rods are a totally new product using St. Croix's Integrated Poly Curve and Advanced Reinforcing Technology (IPC and ART) as well as the new resin. St. Croix also uses Matrix Resin in several spinning and casting rods.

G.Loomis designed a new rod series from the ground up using a new carbon fiber that Steve Rajeff, director of engineering, says works better with Matrix Resin than any other he's tested. The NRX rod series includes 16 fly rods for fresh and salt water, and Spey casting, as well as 13 casting and spinning bass rods. [For details on NRX, see Hatches, page 21. The Editor.]

Hardy has announced a new fly rod series called SINTRIX. Officially, the company did not credit 3M with any additive, but in a press release wrote "SINTRIX, short for silica nano matrix, is a new formulation of resin that binds the carbon fiber and reinforces the blank to such an extent that broken rods may be a thing of the past." The new Hardy rods will launch in January 2011.

Temple Fork Outfitters is also developing a new rod series with the resin, but no brand name or release date has been set.

While the widespread use of Matrix Resin seems to democratically indicate that the product makes stronger rods, the vote has not been unanimous. Sources at two other major rod companies say they have tested the product and still prefer their current resin systems. Tom Rosenbauer at Orvis says flat out, "our thermoplastic resin is stronger."

Ross Purnell is editor of Fly Fisherman.

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