Epoxy Test - USC vs. MAS vs. RR vs. MGS
O.K. gang. I've been receiving quite a few questions about several different epoxies that I've been using. I'm trying to really find out how 3 low cost resins stack up against the premium MGS resin. The following is a comparative analysis.
The data and impressions being posted here will accumulate, so, you might want to hold on till the end before making any decisions. Also, compatibility between release agents, mylar usage, etc has yet to be tested. Once all the testing is complete, I will post my personal Excel spreadsheet data for your perusing.
I will be be doing testing for room temp. cured parts, parts cured at 125*F, and observations of the sample parts at 115*F.
EPOXY RESINS BEING TESTED
US Composites 635 (USC)
3:1 or 100:33 mix by volume
100:31 by weight by weight
Fast and Slow Hardener available - I do NOT recommend the slow hardener.
MAS Low Viscosity (MAS)
2:1 or 100:500 mix by volume
100:45 mix by weight
Fast and Slow Hardener Available - can be mixed to cater the working time.
Resin Research Composite Pro 2070 (RR)
3:1 or 100:33 mix by volume
100:30 by weight
50 and 200 minute working time hardener available
MGS 285 (MGS)
2:1 or 100:50 mix by volume
100:40 mix by weight
3 Hour working time hardener available. Hardeners can be mixed to cater the working time.
COST: USC resin is the cheapest at $61 for a gallon kit (resin + hardener=1 gallon). Next Comes RR at $74, MAS for $80 from HERE, and MGS for $136 per gallon. Note that the prices listed are for a gallon mixed (resin + hardener). Shipping costs can vary significantly, so shop around for the best price (specifically for MAS). CST and Aircraft spruce are the only ones that I know that sell MGS. USC is only available from uscomposites.com. And the RR 2070 is only available from resinresearch.com.
VISCOSITY:: The follow is based on my impressions (no scientific test) and not based on the ratings posted by the manufactures. I found the USC to the thickest of the batch, MAS was slightly thinner than USC, RR was noticeably thinner than USC and MAS, and MGS was MAYBE ever so slightly thinner than RR. Honestly, it's difficult to differentiate between RR and MGS. If I had to decide, I'd lean towards the MGS have the lowest viscocity.
WORKING TIME at 75*F:: The parts that were laid-up for testing were small, so the end of the working time was never reached. The following impressions are a best guess. I'd say that the USC, MAS, had around 25 minutes of working time at 75*F. I'd say that the RR was less around 20 minutes. The MGS will give you around 30 minutes of working time.
ODER: The oder of the MAS epoxy was the most bothersome. The USC, RR, and MGS didn't bother me. The RR seem to have the most un-noticable oder. This is obviously very subjective.
COLOR: The USC has a light amber color due to the hardener, the MAS is clear, RR is the clearest of the batch, and the MGS is light blue do to the hardener color.
Last edited by wyowindworks; Nov 03, 2009 at 01:46 AM.
Workability & Mold/Lay-up Detail
I made the molds for the test lay-up from 2.5 inch PVC pipe. I cut the pipe into 4" long sections and then split them along a fence on the band saw. A hose clamp is used to hold the halves together. The molds are open on both ends and large enough enough in diameter to easily work the seam. Each resin has it's own mold. Since the testing is comparative, it's important that the parts being compared are cured at the same time and at same temperature.
The lay-up consists of 1 layer of 2 ounce glass on straight, 1 layer of 4 ounce glass on straight, 1 layer of 4 ounce glass on bias, and a second layer of 4 ounce glass on straight.
The fabric was cut using a template in stacks so all the fabric cuts end up being the same size. The fabric cuts are 3" wide and 3.25" long. The part will be joined using a wet seam. The layers will be progressively staggered so the seam will be consistent and strong.
The 3" demolded part will be trimmed to a length of 2 3/8" using a jig to insure that the parts are the same length and contain the same amount of fabric.
The PVC molds were waxed with 4 coats of Part-all Paste #2 and then wiped with a thin film of Part-all Film #10 (PVA).
The epoxy pot consisted of 10 grams of resin + the appropriate amount of hardener. The measuring was done by weight using a gram scale that's accurate to .01 grams. The hardener was added to accuracy of .05 grams.
So, how usable were these resins??????
Technique: The mold was painted with resin and the 2 ounce glass was laid in and brushed till saturated. The next 4 ounce glass was then laid in and brushed with more resin until saturated, the next layer of 4 ounce (bias) was added and brushed with resin till saturated. The last layer of 4 ounce is added, but NO ADDITIONAL resin was used to saturate the fabric. Only the extra resin in the lay-up and brush could be used to saturate the last layer of 4 ounce fabric. No dipping into the pot was allowed on the last layer.
Both the USC and MAS resins saturated the fabric nicely. I would say that these two resins were about the same in respect to fabric saturation. I was able to complete and join these lay-ups in about 11 minutes each.
The RR saturated the fabric noticeably easier than the USC and the MAS. I was able to complete and join the lay-up in 9.5 minutes.
The MGS also saturated the fabric easier than USC and MAS, I was able to complete the lay-up and join in 10 minutes.
The real surprise was the RR. I would have to say that in respect to fabric saturation, RR may be slightly better than MGS.
JOINING THE WET SEAM
When it came to joining the wet-seam, USC was probably the easiest to join and made the highest quality seam...probably due to the higher viscosity. The second easiest seam was the RR, then the MAS. The MGS seam was actually the most fussy. The seam could be pressed together, but would lightly pull apart making small bubbles.
I must admit that the seaming observations are very subjective. Typically when wet seams are joined, the resin is at it's end of usability and becomes quite tacky. Also, resin content in the seaming area and fabric stagger all play a part in the ease of making a wet seam. The above observations could only be confirmed by making many, many parts and seams.
The next installment will contain the curing and demolding rates.
Last edited by wyowindworks; Nov 01, 2009 at 08:46 PM.
Room Temperature Curing Rates
The following curing observations were made at a environment temperature of 75*F. This just turned out to be the temp. of my shop at the time of the test. Each observation was made based on when the mixing of the epoxy was completed. A sample of epoxy was mixed, the lay-up was done using that epoxy, then the next sample was mixed, the lay-up done using that epoxy, and so on. All the observations are accurate to within 2 minutes.
The observations were made by inspecting the remaining epoxy in the pot. Each pot weighed approximately 6 grams. At 6 hours, the parts were demolded and observations were made of the parts themselves as well as the pot.
1 Hour After Mixing:
RR: Very Tacky
Pot Set Firmest to Softest: RR, MAS, USC, MGS
2 Hours After Mixing:
USC: Sticky and Stringy
MAS: Tacky, left fingerprint
RR: Hardest, Tack-free, makes a fingerprint with firm pressure
MGS: Sticky and stringy
Pot Set Firmest to Softest: RR, MAS, MGS and USC tie
3 Hours After Mixing
USC: Tacky, leaves fingerprint
MAS: Tack-free, fingerprint
RR: Cannot make a fingerprint, can mark with a fingernail
MGS: Tack-free, leave fingerprint
Pot Set Firmest to Softest: RR, MAS and MGS tie, USC
4 Hours After Mixing
USC: Tack-free, leave fingerpring
MAS: leave fingerprint
RR: Cannot make a dent with a fingernail
MGS: leaves fingerprint
Pot Set Firmest to Softest: RR, MGS, MAS, USC
NOTE: The RR part was demolded at this time and was surprisingly firm.
5 Hours After Mixing
USC: Fingerprints can be made.
MAS: Fingerprints can be made
RR: Can no longer scratch surface with fingernail
MGS: Small dent with a finger nail high pressure
Pot Set Firmest to Softest: RR, MGS, MAS, USC
NOTE: The MGS part was demolded. The MGS part was softer than the RR part.
6 Hours After Mixing
USC: Pot now firmer than MAS, Dents can be made with fingernail
MAS: Dent can be made with fingernail
RR: Pot very hard
MGS: Pot can still be light dented with hight pressure from fingernail
Pot Set Firmest to Softest: RR, MGS, USC, MAS
Part Set Firmest to Softest: RR, MGS, USC, MAS
NOTE: All parts were demolded
8 Hours After Mixing
USC: Light mark with fingernail
MAS: Light mark with fingernail
RR: Very hard pot, stiffest part
MGS: Cannot dent or scratch pot with fingernail
Pot Set Firmest to Softest: RR, MGS, USC, MAS
Part Set Firmest to Softest: RR, MGS, USC, MAS
EARLIEST POTENTIAL DEMOLD TIME AT 75*F
USC: 12 Hours
MAS: 12-14 Hours
RR: 5-6 Hours
MGS: 8 Hours
NOTE: I would personally leave the parts in the mold longer than the above possibilities. Parts demolded at these times should be handled with care. Distortion is possible especially with USC and MAS.
CONCLUSIONS IN RESPECT TO PARTS
The resin research is by far the fastest setting epoxy at 75*F. I would seriously consider demolding fuse parts in 5 to 6 hours. I was quite surprised by this epoxy. Even the part demolded at 4 hours was firmer than the USC and MAS parts demolded at 8 hours. The working time of this epoxy is the shortest and is also going to give the shortest green-trim window. The difference between too soft and too hard for green-trimming is very short. The MGS epoxy set slower than the RR but serveral hours quicker than the USC and MAS. It has possibly the longest working time, but still set quicker than USC and MAS. It would have a longer green-trim window than the RR, but one would have to wait longer before trimming than the RR. Since the RR has a shorter working time (20 minutes) one would have to work pretty quickly. Also, the fasting setting time could be problematic for lay-up that are done in stages (each mold half done with a seperate mix then joined for example) since it gels in 1 hours. That would really be problem on a complex a lay-up. The working time can be extended to 50 or 200 min with other hardeners.
MAS and USC had very similar setting traits. Initially the USC was softer than the MAS. After 5-6 hours the USC pasted MAS in firmness and started to set a little quicker. The trim window is very similar between these two resins at 75*F. One would have to wait the longer to green-trim than RR or MGS, but the green-trimming window would longer.
All the reasons released very well with wax and PVA. I have not tested any of the resins with wax only. RR resin diminishes the gloss is Frekote treated molds. For this reason I don't consider it compatible with Frekote. MAS epoxy lightly diminishes the gloss of Frekote treated molds. MGS and USC work will with Frekote treated molds.
CONCLUSIONS IN RESPECT TO MOLD MAKING
The RR epoxy would make for a very quick setting surface coat when combined with the appropriate fillers. Layer's could be added to this epoxy in nearly 45 minute intervals. If one was doing two coats of surface coat the backing could be applied in 2 hours from start time. The first coat would be getting very hard by the time the backing was beginning to green. The quick setting time could (only testing will tell) protect the mold from fabric telegraphing. Gel-coats that set very slowly tend to telegraph the fabric pattern into surface of the mold if coarse fabrics are used. The downside to RR epoxy is that it dimishes the gloss is molds treated with Frekote mold release. It is very safe for any molding procedure including a PVA barrier. One potential issue with RR could be that of telegraphing because of it's fast curing rate. Fast curing resins tend to shrink more than slower setting resins. I will be doing a gel-coat test to see how it performs. Also see post #23 for observed telegraphing issues in parts. EDIT: AFTER MORE TESTING, I WOULDN'T RECOMMEND MAKING A MOLD WITH RR AND THE 3100F hardener.
MGS would also well for making molds, but is ridiculously expensive for making molds. I'm considering making my surface-coat in molds with MGS because it's Frekote safe (I use Frekote to make my molds) and cures ahead of a USC backed mold reducing telegraphing of heavy fabrics. Downside to MGS (outside of expense) is that it takes quite awhile before the surface becomes tacky and the next phase can begin. I would not recommend backing an MGS surface coat with RR. RR would end-up curing ahead of the MGS and would make the surface prone to fabric telegraphing.
USC and MAS with their medium hardeners would make a poor surface coating for molds because it's set time is very slow and they remain too soft for too long. Telegraphing is prone to occur and the waiting time between phases is very long. I always use the fast hardener when making a surface coat with USC.
NOTE: I DO NOT KNOW HOW THESE RESINS BOND WITH EACH OTHER. MIXING RESINS IS NOT RECOMMENDED.
I'll make no conclusions about the stability of the molds until later.
Next we do some deflection testing......
Last edited by wyowindworks; Nov 10, 2009 at 12:21 PM.
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Let me know and ill send you some
Deflection Testing at 20 Hours - Room Temperature Cure
In this test I use a homemade apparatus to measure how much the test parts deflect under a similar weight after 20 hours of curing time. The apparatus consists of a platform with a groove to stabilize the round test piece and a tower that stabilizes the load applied. The tower consists of a precision linear bearing with a small shelf to hold the weight. Again, the test is comparative.
Before this test could begin, the samples were trimmed using a jig to make sure that they were all the same length. The edges were removed to insure that the fabric content was consistent through the entire piece. The parts were the cleaned to remove any dust and PVA, allowed to dry, and then weighed. The part walls were also measured. The wall thickness was very consistent throughout all the parts at around .021". The fabric stack measures .015", so, the epoxy added about .006" in thickness to the walls of the part.
USC: 8.13 grams
MAS: 8.02 grams
RR: 8.04 grams
MGS: 7.90 grams
Generally, their weights were very close. I in no confidence could say that any one resin made lighter parts than the others. There are just too many variables in a hand lay-up (no vacuum bagging) to consider the above weights conclusive.
Essencially, the part is placed into the apparatus and a force is applied. A measurement of the height is taken before and after the weight is applied. Again, this is comparative. The same weight is used on each test sample.
Deflection for 1x
Description: A measurement is taken before and after the weight is applied. The difference of the two measurements shows how far the sample was distorted by the weight.
MAS: 5 mm
RR: 3.5 mm
MGS: 4 mm
Stiffest of Softest: RR is stiffest, then MGS, and USC and MAS tie for softest
Deflection for 2x (twice the initial weight)
Description: The test is just like the above test, but twice the amount of weight is applied.
USC: 11.5 mm
MAS: 12.5 mm
RR: 9 mm
MGS: 9 mm
Stiffest to Softest: MGS and RR tie for stiffest, USC, then MAS
Deflection Over Time
Description: In this test one weight is applied for a duration of 10 minutes. A measurement of height it taken after the weight is applied, and then a height measurement is taken after the weight has been applied for ten minutes. The results below show how much the part "settled" during the ten minutes of applied weight.
USC: 1.25 mm
MAS: 3.5 mm
RR: .25 mm
MGS: .25 mm
Resistance to settling: RR and MGS are the most resistant to settling, USC settles some, and the MAS is most prone to settling.
Return to Shape
Description: This observation measures how quickly the part returns to it's original after the weight has been applied for 10 minutes.
USC: Returned to original shape in about 5 minutes
MAS: Never returned to it's original shape after sitting unloaded for 10minutes. It was approximately .75mm shorter than it was originally. The part has been restored by returning to the mold.
RR: Returned to original shape immediately
MGS: Returned to original shape in 3 seconds.
Resilience: RR and MGS most resilient, USC is resilient but took longer, MAS never returned on it's own.
Parts made with RR and MGS are equally the stiffest after 20 hours of cure time. USC parts are in the middle, and MAS parts are the softest after 20 hours. The above test really shows the soundness of the parts after demolding. Caution should be used with MAS parts as they can be distorted and not come back to their original shape on their own. Caution should probably also be used with parts made with USC as these parts are slow to return to their original after a stress is applied.
Molds made with MAS epoxy should definitely not be put into service after only 24 hours of curing. The pressure of bolts, clamps, and simple use would definitely distort the mold irreparably. Molds made with USC should also be allowed more curing time. RR or MGS made molds could under go light use....if you were desperate. Typically, though, I like to let my mold cure for 7 days before use.
ONE LAST NOTE: This test will be conducted once a day for the next seven days. Tomorrow well will also test them at 115*F.
Last edited by wyowindworks; Nov 03, 2009 at 10:39 PM.
Very interesting tests and thanks for sharing - shame none of the brands apply this 'side'.
How did the health and safety stack up for the different systems? Over here, it seems the more you pay the better the H&S (as well as mechanical performance).
Always watching with interest,
Carbon Nanotube Epoxy
I think the sample quart was about a hundred bucks. I picked it up to try on some spar tests. I dont know if what your testing here in this thread would show the benifits as much, but it looks like it should make a stronger part.
I am going to do some layups today and ill try to make a few sample spar sections with carbon tow.
Thanks again for sharing this. I am still sold on the MGS.
From your data on pot life and hardness after initial mixing it would appear thta the RR resin uses a faster and more aggressive curing agent than the MGS. Some aliphatic and cyclo aliphatic curing agents tend to do this. I could not tell which curing agent they have used but it appears to generate greater cross-link density faster.
The faster the cure, the greater the shrinkage usually.
I would think a slightly longer pot life for the RR would be a benefit for tooling or complicated lay-ups. Do they have a similar viscosity material with a slow gel time?
Two additional test that may make sense:
1. Post cure at 140F and check deflection
2. Solvent wipe test- wipe "cured" part with acetone and see if the part is gooy or any resin transfers to the rag- this indicates uncured monomer/polymer that did not cross-link.
You might also consider
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