FRN, G10, etc.

[Alan]

Greetings:



Perhaps this has been discussed before and I missed it but I am very curious about the material properties and manufacturing processes associated with making a knife with FRN scales versus G10 scales.



My main interest is just that I'm curious but several posts in the General Forum and on the Spyderco Forum at BFC served as a catalyst for me to ask this question. In those posts many expressed a preference for G10 over FRN for the new Vesuvius. I happen to have a Vesuvius and I'm quite impressed with the FRN. I'm sure that some of the material properties of G10 and FRN can be measured using standard testing methods for things like shear strength, elasticity, rigidity etc. (I'm not an engineer so my terms might not be very precise). But even these sorts of numbers may not be very useful for comparsion between the materials in actual use in a product such as the Vesuvius because it is the aggregate properties of the FRN (or G10) with integral metal liners (and the attachment to the rest of the knife) that determines the ultimate performance.



Also, as far as manufaturing processes are concerned. Am I correct in assuming that materials like Micarta and G10 are only available in flat stock and then must be machined whereas FRN can be custom molded (albeit not always with ease) to a specified shape?



Again, I'm just curious and would love to hear from Sal and other Tekno-Junkies on this issue. I'm not seeking any proprietory information but rather I'm just curious how these things are built and the tradeoffs between materials. Thanks, Alan

[Carlos]

Here is my crash course is plastics. Pay attention -- there will be a quiz afteerwards. <img src="wink.gif" width=15 height=15 align=middle>

There are two basic types of plastic in use for knife handles, thermoplastics and thermoset plastics. Thermoplastics are usually described in having &quot;wax-like&quot; properties -- heat softens the plastic which allows you to form it under pressure. Reheating also allows you to reform it. Thermoset plastics in turn are &quot;cured&quot; under heat and pressure into a permanent set form.


Thermoplastics:

In the group of thermoplastic resins we find nylon, which is used for Fiberglass Reinforced Nylon (FRN) knife handles. The most well known form of FRN in Dupont's Zytel. The nylon is reinforced by adding a &quot;glass fill&quot; (by weight) of 10% to 45% with short E-glass filaments. Zytel has about a 30% glass fill -- making it very strong and rigid. The Swiss polymer GV6H (used only by EDI) has an unusal 60% glassfill. The various FRNs are used primarily for their light weight and low cost, and because they can be injection molded into complex shapes.

Kraton is a black thermoplastic rubber that is used a great deal by Cold Steel, and as an insert in aluminum handles by many knife manufacturers. It has poor resistance to heat and solvents.

&quot;Kydron&quot; is a Kevlar Reinforced Nylon being used by Emerson Knives for its Raven models.


Thermoset plastics:

In the group of thermoset plastics we find G10 and Micarta. G10 is a standard industrial laminate grade of NEMA (National Electrical Manufacturers Association), while Micarta is a proprietary trademark belonging to Industrial Paper. Thermoset laminates are typically composed of two components: A continuous woven cloth of glass, cotton, graphite, etc., and a thermosetting resin that binds the layers of reinforcing cloth into a single unit. The resins vary from epoxies (G10, carbon fiber), phenolics (micarta, carbon fiber), polyester, etc.

G10 consists of a woven E-glass fabric that is bound by a thermoset epoxy, with a typical glass-fill weight of 40% to 70%. Due to the expense of molding any cloth based laminate, G10 for knives is usually machined from standard flat sheets of G10. Most G10 handles are also sandblasted with a coarse medium at low pressure to reveal the texture of the fiberglass weave. It is prized for its chemical, heat, and electrial resistance, its strength and rigidity, and its low weight.

Micarta is a lamination of either a paper, cotton, linen or other oraganic fabric with a phenolic resin binder. If you want an explanation of &quot;phenolic&quot; check your Britannica, as it is over my head to explain it. I will just say that is has high strength and electrical resistance.

&quot;Carbon fiber&quot; is a blanket term for laminates using carbon fiber fabric. I have seen the binders vary from phenolics to epoxies. There is no way to be sure of exactly what you are getting when a knife manufacturer uses &quot;carbon fiber&quot; handle scales.

***I should note that thermoset laminates can be produced in molded shapes but is usually not due to the expense of laying up each scale by hand.

[Alan]

Thanks Carlos!

To make this very simple so I understand let's consider the tradeoffs for just two materials and a single design: G10 and FRN as each would be implemented on a piece like the Vesuvius.

FRN
Nominally more lightweight
Less expensive to produce (say about 20-30% for MSRP)
Molded

G10
Nominally heavier
More expensive
Machined
Generally grippier

QUESTIONS
Strength and stiffness differ but it seems doubtful that especially with this design with metal liners that this difference would affect performance for the intended function. Thoughts, experience?

[cerulean]

My understanding is, basically: Micarta is stronger than FRN, G10 is stronger than Micarta, and carbon fiber is stronger than G10. Will you see the difference in strength in a normally used pocket knife? Probably (well, almost certainly) not, but it's a selling point.

The more snobby knife nuts may dislike FRN in particular because it lacks texture and doesn't feel &quot;solid&quot;. It's hard to describe, but FRN has a &quot;plastic&quot;, &quot;cheap&quot; feeling to it that reminds people of disposable, throw-away products.

I personally don't mind FRN; it's a great, inexpensive handle material for a using knife. Some people will probably be prejudiced against it no matter how it's put in a knife though.

[Carlos]

G10 is stronger and more resistant to heat and solvents than FRN. Of course FRN is as strong as 99% of us need, and heat and solvents that would deform and/or dissolve FRN would do the same to the person holding the knife.

The strength and stiffness gains of G10 over FRN are best realized at this time with a nested lock construction, where the forces bear directly on the scale. In a pinned scale contruction, the forces bear on the pins and the strength of the scale material matters less. This is also true for carbon fiber laminate.

Actually the full potential of the continuous weave thermoset laminates won't be fully realized until we see the same molded monocoque contruction used for high-end racing bicycle frames and F1-type chassis. The next step towards this is individually molded scales, which allows not only for more ergonomic shape, but for the behaviour of the scale under stress to be precisely tuned for the application -- we will see this in the upcoming Temperance series.

All that said, the main reason to choose G10 over FRN at present is the way it feels. Even though they are quite light, high-quality G10 and carbon fibre laminates have a wonderful dense solidity that is lacking in FRN.

Edited by - Carlos on 5/16/2001 6:33:52 PM