Dynema

General Composites Discussions Products Talk
#1

I’m not sure which big company owns the Trademark name of Dynema, but let me tell you… this stuff is stronger than steel. It comes in different forms. Even the high grade fishing line is made of it, because it is so strong it can be made much thinner than normal test fishing line. I bought some a while back that was “bow thread” used in making compound bow strings. This thread was about .005 diameter and hard as heck to cut with sharp scisors. It’s claimed to be 40% stronger than Kevlar. Now it seems it is finding it’s way into the composite world :cool:

http://www.extremesupply.com/vemarhelmets/vemarhelmetsvrx4.htm

http://en.wikipedia.org/wiki/Ultra_high_molecular_weight_polyethylene

http://www.compositesworld.com/hpc/issues/2005/May/845

edit: i was looking online for who makes dyneema fabric and only came up with a link to BGF Industries Inc. located in South Carolina. 336-545-0011

#2

Wasn’t Dyneema the ballistic material that degraded, and got a few police killed, because their vest’s failed after only a year? Or was that something else?
Fast, I’ve been working with SpectraShield for a few months now, the stuff is a bitch. It takes FOREVER to cut through with kevlar shears (one full closure of the sissor will only get about 3/4" inch cut). Post-production, even more of hell. It’s cut/abrasion resistant, which means…you can’t cut it without making a mess of fibers.
Dyneema might be the same, being a UHMWPE.
Though, Spectra IS light!
(it’ll float)

#3

so is this the same as spectra???

The stuff that was degrading in vests was zylon.

#4

Yep, Dyneema and Spectra are the same thing, but just different trademark names.

I too read on the web that dyneema vests failed bullistic tests. I’m not sure if they fixed the problem, or just quit making bullet proof clothing/vests with the stuff. However it is great for other uses. It is a real pita to cut the stuff. I think the light weightness of it comes from being able to use less material to do the same job of other materials.

#5

I recently purchased a yard of 23oz (or 18 cant remember) spectra that i will likely try out tomorrow.

#6

so I experimented with some spectra tonight. Extremely interesting material. This stuff is increadibly difficult to cut. My scissors that cut kevlar had to be adjusted and tightened just to cut through this. Bear in mind this is a heavier fabric than the kevlar I usually cut (23 oz vs 12oz). I used an expensive higher temp epoxy on this stuff. In order to wet out the fabric, I was forced to use the heat gun on the wet spectra to reduce the viscosity and still was difficult. Same deal as fiberglass as it is wetting out (aka becomes clear). As i clamped and used the heat gun, the dry parts of the fabric the heat gun blew over started to melt…This stuff has a very low melting temperature. This does not work overly well for my uses but may in the future. I will posts pics of the final piece as well as strength of the part once it has finished curing…

#7

Ah, Zylon! that might be it.
They make dry spectra fabric? I thought it was only the 0/90 prepreg (well…it IS PE, with more PE as a matrix). Yup, bitch to cut :slight_smile:
What were you trying to make?

#8

Well, it’s also polyethylene…so it’s a very low specific gravity material. I just saw some Modern Marvels show on bullet proofing (of course I stayed up late to watch it), and they say they can braid Spectra fiber into ropes, that not only are 7x stronger than steel, but float.
Dang.

#9

I impusivly bought the spectra since I had never seen it before. I am just testing a part since i’m interested in the material. The 15.5 oz spectra I have is similar in thickness to the 32 oz glass I have been using for a while. For my applications, heat resistance is typically important. This looks like an excellent material to use if heat is not a factor. If i get a chance to post cure the material i will let ya know about weight and strength.

#10

Well from what i’ve seen I am unimpressed by spectra.

Cons:

Impossible to cut
Low melting temperature
not overly strong
difficult to wet out.

Pros:
Stupid light material.

I have made a sheet from 2 layers of 15.5oz which is considerably thick when using this material. The plate has been post cured but does not exibit very much strength at all. The plate I made was done using epoxy which was heated and compressed with a ton of clamping weight.

#11

Well, I don’t think it’s meant to be strong, like CF will be. it’s a ballistic (and rope) material. It will stretch alot before it breaks. I’ve made several 1/4" panels, and they still bend.
That is why our main project will be almost an inch thick.
We press our 12x12 plates at 7.50 tons.

#12

gotta ask. did you buy spectra shield woven farbic, or 0/90 sheets? I ask because the only spectra I’ve seen is a thermoplastic. It doesn’t use epoxy.