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Epoxy resins - strength and suitability 11 Dec 2013 00:28 #607

good point kenny on how the resin holds the layers together under tension in a de lamination situation.
i got the impresion that epoxy was carcenogenic from a of bert ranton/rutan? book...a chapter on safety....think the book was called moldless composites?
if the epoxy is not carsonogenic.....was it the hardener?pehaps a quick google search will tell......any way in this surcumstance considering other resins,i think would be a smart move?it does not hurt to open our minds to all options...seems to me although an epoxy can be the best it terms of strenth...the rest are very very closein ...there are some old wood gliders here still flying glued together with glue made from milk....if a particular epoxy is not carceonogenic...... there is still a problems with supply/postage/cost........and id also like to add that a sensitization to epoxy is not something that should be taken lightly,its a serious emun reaction and i do remember reading some were that the epoxy's interfear with your hormones.but i cant tell you were i read that.......any way phill id be interested to hear your comparisons on other resins and if they are toxic as well if you feel like comparing?
i personaly would like to move away from epoxy.actually if i ever get back to this fuselage,i will move away from epoxy,unless i see a good reason that is.
russ.



On Tue, Jan 3, 2012 at 1:00 PM, <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:



Phil,

Yes the Aeropoxy reported tensile strength is dominated by the glass, epoxy is not that strong 8,000 to 12,000 is a common range for neet epoxy. You should never trust a manufacturers data sheet to use as design numbers. The Tg reported is most likely a post cured number as well I think Aeropoxy is around 155 F before post cure but I would not post cure them as it takes a large oven. The sun method is too uncontrolled to get an even temperature and post curing is ramp rate sensitive. The ramp rate has to be slower than the Tg curve or it will soften and distort.

Epoxy components are not carcinogenic but they are sensitizers with repeated exposure you can become allergic to them. So gloves, good ventilation, and if you get the components on you wipe all you can off with a paper towel then wash with soap and water or a citrus hand cleaner. Never use a solvent to clean epoxy off of skin it will remove the oil barrier and dissolve the epoxy allowing it to be carried into the body. If you become allergic to epoxy, it is for life your reaction severity depends on your body chemistry. It is like a bee sting some people are not affected and some have violent reactions. Most common reactions are skin dermatitis and swelling of the mucus membranes i.e. airways.

Aeropoxy is not a good infusion resin.


Regards,

Charlie Johnson
Composites Materials Engineer
Ogden Utah

In a message dated 1/2/2012 9:47:25 A.M. Mountain Standard Time, This email address is being protected from spambots. You need JavaScript enabled to view it. writes:
Hi Folks,

I'd like to pick your brains on the subject of epoxy resins...

In planning this project I came across a recommendation by Jim Marske for a resin called Aeropoxy - excellent strength and workability, and a high Tg temperature following post curing. The only problem is that importing Aeropoxy from the States to Ireland (it can't be got here in Europe) is prohibitively expensive as it is classed as a haz-mat substance by the airlines. It is also not well suited for using in Vacuum Assisted Resin Infusion - it's too thick / viscous.

I have come across another resin supplier, in the UK, and much closer to home, who is able to supply Infusion Resin in volume at a reasonable price. Easy Composites IN2-Infusion-Resin is a possible alternative, and I'd welcome any comments or observations on the suitability of this product for use in building a Carbon Dragon.

There is one significant difference in the post-cured properties of the two resins - the IN2 Inusion resin appears to have a much lower Tensile Strength. Given that the carbon fiber is carrying the lion's share of the load, is the tensile strength of the epoxy actually that important?

Aeropoxy Easy Composites
PR2032/PH3665 IN2-Infusion Resin


Viscosity (cps=mPa.s.) 925 - 975cps @ 25C 225mPa.s. @ 25C
Pot Life 120mins 80-100mins
Glass Transition Tg 194F / 90C 201-212F / 94-100C
Cured Hardness 87 Shore D 84.5 - 88.5 Shore D
Tensile Strength 45,870psi (=316MN/m2) 65.5 - 73.5 MN/m2


The data sheet states that the tensile strength of the Aeropoxy was derived from a 10-ply laminate hand lay-up using style 181 fiberglass fabric, 55% glass content. No similar information is given for how the data for the Easy Composites IN-2 Infusion Resin is derived. Given the huge disparity in the tensile strengths of the two resins, could the Easy Composites data be referring to the tensile strength of the un-reinforced resin alone (no CF involved)?

You can find the data sheets for both products here:

Easy Composites IN2 - www.easycomposites.co.uk/downloads/TDS/E...2-Infusion-Resin.pdf
Aeropoxy - www.ptm-w.com/dynamicdata/data/docs/PTM_...neCatalog30Jun06.pdf - pg.32-33

Happy New Year all,

Phil.

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