I am curious if anyone of the old timers have an answer for what the IM stands for

Example: IM7 graphite

I was told by an old timer in Oregon that back in the day the military was experimenting with graphite and certain resins for a type of light weight armorment. He told me the IM stands for "Improved Military". Heck, it sounds good to me.

Anybady know what it stand for? Just curious.

David Banaka

Intermediate Modulus. Any graphite with an elastic modulus in the range of 36,000 to 45,000 ksi. The number following IM is basically meaningless, as it varies from company to company, for example Cabela’s IM6 is 38,000 ksi while Rainshadow's is around 44,000ksi. Indecently, Cabela's "high modulus" IM7 is also around 44,000ksi, so there is a fair bit of marketing going on with how blanks are labeled.

Interesting. Thanks for the information.

Your assumption is correct. The term IM originated from the military. Intermediate modulus is a relatively new phrase that means absolutely nothing.

David,
I have heard both explanations IM=Improved Military and IM=Intermediate Modulus. I am inclined to believe the Improve Military because the suppliers of the prepreg (material used to make blanks) have material that they call IM6, IM7, IM8, etc. but the larger manufacturers of blanks do not use the term because they are not using these prepregs. They are not using them because they can get prepreg that is cheaper that has the same modulus. I think that Daniel and Patrick are also correct that it is now a term that is primarily used for marketing purposes. If you notice these terms are now being used primarily on inexpensive import blanks.

I know about graphite modules and how the makeup works. I was just curious about the "IM" I pretty much knew about the marketing deal, IM, IMX, and so on. I am a veteran so the IM, Improved Military sounded good to me.

People ask and I like to give an accurate answer.

Thank you all

David Banaka

David, I think you asked a good question because it does come up often without any real good answer, and I know others also have the same question on their mind from time to time.. The IM "grade" (IM6, IM7, etc), from what I understand, isn't even relevant to the performance or quality of the rod or the rod materials, suggesting instead, the number designation is the last number of the federal stock number assigned to the material. I use it as loose reference for comparison, but I don't put my faith in it as the sole selection criteria. If you do a search using "improved military" as the criteria, you will find a discussion string from Feb 2003 that does provide additional insight.
A search on the web provided information on improved military, but nothing about the cloth used to build rods. I think if I had a good stock number, I would bet I could fnd something about it on the internet. The bottom line is, whatever designation it is, the stuff has done wonders for the rod building industry. It's a generic military term for everything from gun powder, to weapons systems, to tp.


Patrick Vernacchio

For those that want to know a little more about this subject here is some data taken directly from a Cape Composites data book.
IIM# Tensile Modulus(MSI) Tensile Strength(KSI)
IM4 40 600
IM6 40 760
IM7 40 780
IM8 44 790
IM9 42 920

Emory....

Typo?? IM8 - 44 @ 790
IM9 - 42 @ 920 --- Should be 52 ??

Ken,
No, I looked again. Those numbers are correct. The IM8 has higher modulus but the IM9 has MUCH higher tensile strength. Actually I am a bit surprised that a lot of blanks are not being made from IM9 with that kind of tensile strength. That kind of tensile strength would mean that it had a lot higher strain energy or toughness as well. I looked at the other characteristics of IM9 like strain ratio, tow count and it appears to be an excellent graphite. The only thing that I can guess is that it is very expensive. I do not have the prices.