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Penetrating Epoxy Resin

The Real Story

 

 

 

 

 

 

 

 

WHAT THIS SITE COVERS:

Penetrating epoxy basics

Don't be fooled by amazing claims. Penetrating epoxies are much less than they claim to be

 

The term 'penetrating' epoxy is rather vague. Usually it means an epoxy resin with a lot of solvent added. the solvent(s) soak or penetrate into the wood or whatever taking with it some of the epoxy. The amount of penetration really varies. If solvent or water will not soak very far into your surface, the solvent thinned epoxy will not either. Penetration is also bad with damp or wet surface. There is little physical reason for the epoxy/solvent to be 'drawn into' an area loaded with water. Penetrating epoxies are very watery and usually contain more solvent than epoxy.


 

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pentrating epoxy test

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Epoxy Penetration Tests


 

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BASICS:


The term 'penetrating' epoxy is rather vague. Usually it means an epoxy resin with a lot of solvent added. the solvent(s) soak or penetrate into the wood or whatever taking with it some of the epoxy. The amount of penetration really varies. If solvent or water will not soak very far into your surface, the solvent thinned epoxy will not either. Penetration is also bad with damp or wet surface. There is little physical reason for the epoxy/solvent to be 'drawn into' an area loaded with water. Penetrating epoxies are very watery and usually contain more solvent than epoxy.


Epoxy 'primers' are solvent thinned epoxy often used to seal or stabilize the surface of wood/fiberglass etc. prior to coating that surface with some sort of paint or coating, including more epoxy. The big difference between primers and penetrating epoxies (in a very general sense) is the amount of solvent. Primers are usually 10-25% solvent while penetrating epoxies are/were 50-75% solvent.


Solvents are cheaper than epoxy so these products should, in theory, be cheaper than regular solvent free epoxies. This is usually not the case. You can make your own primer or penetrating epoxy by adding solvent to just about any epoxy. Although it is logical to begin with a thin watery epoxy and then add solvent (like our Low V epoxy), I would simply use a thicker marine epoxy if that is what I had available.


How much solvent is in your epoxy? Most regular epoxies contain no solvents. Penetrating epoxies will list how much solvent they contain in several ways. Consider 10 ounces of a penetrating epoxy. The amount of solvent it contains can be identified in several ways. All the following convey about the same information: 30% solids, 70% VOC, 700 G/L (grams per liter), 6 lbs/gal VOC. This product is approximately 3 ounces of epoxy and 7 ounces of solvents.


A little bit about rot. Wood rot is often a result of dampness and often that dampness is not completely dried away when repairs are made. Best approach is to scrap out as much of the rotten wood as possible, kill the remaining rot fungus by soaking area with anti-freeze. Let dry (weeks) then seal with solvent thinned epoxy (primer or penetrating, probably doesn't matter) then fill hole with a piece of wood and or exterior putty (epoxy putty tends to be too hard to sand easily), then paint. More on rot -
CLICK HERE.


Warming the epoxy will decrease its viscosity and improve penetration. So too will warming the surface it is being applied to. As the object cools, the air in it will contract, helping to draw the epoxy into the object.


As a 'sealer',' 'primer', or 'undercoat' for paints or varnishes, epoxies have proven their worth. No special product is needed here. In my opinion, just about any epoxy, thinned or unthinned, will perform this task in a satisfactory manner.


Because of the lack of true penetration into anything other than very dry end-grain wood, and because of new air quality (VOC) laws and regulations, the terms, "penetrating" and "primer" are rare used by the manufactures of these days. Now, they are more commonly described as "bond enhancers" and/or "sealers". We admit it, our competitors don't!


 

epoxy primer epoxy sealer penetrating epoxy

 

 

 

 

 

 

 

 

 

 

 

Don't be fooled by "out of this world"

performance claims...



My Observations:



1) Even a small amount of solvent noticeably increased epoxy penetration.

 

2) The solvents and solvent mixes generally performed about the same for me in my tests. Xylene seemed work well (best) and is easily obtainable at a local hardware store. It quickly become the solvent used I used in most of my tests. I paid about $15 for a gallon of xylene in a local hardware store.

 

3) Epoxies with a lower initial viscosity before thinning, penetrated better (and were thinner) when solvents were added to them (common sense).

 

4) Even a small amount of solvent greatly affected the epoxy gel/set time. With only 10% -15% solvent the time it took for the epoxy to set (in a 0.5-1.0 inch thick layer inside an open wide-mouthed, pint container) increased from several hours (no solvent) to 1-2 days. With more solvent, gel time could be up to 4 days.

 

5) The additional of solvent made the resulting block of epoxy very rubbery. At 10% this rubbery affect was minimal and slowly went away. At 15% there remained a bit of give to the epoxy blocks. At 33% the epoxy became a rubbery block. At 50% or better, the result was ‘Jello'. The ‘Jello' took several days to form.

 

6) Some epoxies are more affected/damaged by the addition of solvent to thin them. Adding solvents to epoxies will change the pot life of the epoxy. With most epoxies this change is dramatic. But with cycloaliphatic epoxies, which use ring shaped molecules, the affect is less dramatic. Pot life is not extended nearly as much as with 'regular' epoxies. Our ESP 155 epoxy sealer and primer is a high end cyclo - epoxy with about 24% solvent. Adding more solvent doesn't change the working time (pot life) very much. Bottom line: using something like our ESP 155 might be a better option than adding solvent to other epoxies (like our LOW V or Basic No Blush) if you want to keep working time (pot life) from being excessively long (and the epoxy perhaps more 'damaged' by the solvent). That said, most folks are fine with solvent thinning ANY epoxy - especially in warm weather which will greatly shorten pot life.


More on Penetrating Epoxies


Every year or so I take a new look at penetrating epoxies, including our competitor's products. Our competitor's product (we will call it "ABCD") is a penetrating epoxy with almost a cult-like status. Its material data safety sheet (MSDS) shows it to be a blend of solvents (see attached) comprising about 69% of the product, and about 31% epoxy. On the MSDS the solvents are listed in decreasing order (or amounts). Oddly, the primary (first listed) solvent is only identified by its chemical classification number, while all the other solvents are identified by their common name. The first solvent is an "aromatic hydrocarbon" - tracked down by the CAS number, this product is Type 1 petroleum Naphtha. The second in xylene, a very common (and our favorite) epoxy solvent and thinner. Next comes toluene, another very common paint solvent. Next is isopropyl alcohol (a common solvent, sold in both paint departments and in drug stores). Very likely these 4 very common solvents make up most of the solvents in the product (on a percentage basis) although 15 additional solvents are also included. More on the solvents in this product -
Click Here.



I wonder why so many solvents? Perhaps to discourage anyone from making their own version of ABCD. In my past and current round of testing, I didn't find huge differences in the performances of the several different solvents I used in my penetration testing, although some worked slightly better than others.

 

Also, our product (ESP 155) uses a very high end cycloaliphatic epoxy - instead of the very low end epoxies found in other solvent thinned epoxies of this kind. The brand above uses so little epoxy it doesn't even offer epoxy info in its msds sheet.


 

 

 

Why ESP 155 epoxy sealer and primer is the BEST in its class:

1) Uses superior CYCLOALIPHATIC curing agents and epoxy ADDUCT formulation

2) solvent based for better penetration

3) moisture tolerant, very low viscosity

4) strong user support / feedback

4) 24/7 support

 
 

 



HOW I PERFORMED MY TESTS:


I generally mixed up 6 oz test samples in plastic cups. I measured penetration by inserting a cardboard strip into the test sample and seeing how far up the strip the test solution traveled. The test solution turned the cardboard from light tan to dark brown. This dark color remained long after any solvent might have evaporated away turning the cardboard back to its original color (this was never observed). I had similar results using wooden paint stirring sticks in the solutions, although the affects were more pronounced and easier to observer using the cardboard.

 

 

penetrating epoxy


 

 

 

 

 

 

 

 



REMARKS/OBSERVATIONS:


I have always questioned why ABCD has so much solvent and so little epoxy. Thinning epoxy 10-25% with solvent seems much more reasonable. However, I observed that penetration is greatly increased when the solvent % (by volume) exceeds that percent of epoxy. In other words, more solvent than epoxy. This was something new to me. I still believe that from priming surfaces the 10-25% dilution is right, but is maximum penetration is the goal, the first coat should have excess solvent.



For my initial tests I used our ESP 155 epoxy primer, which is already approx. 24% solvent. I then added equal amounts of solvent to the ESP so total % of solvents in my test cases were about 74% (vs. about 69% for ABCD).
This product is a Progressive Epoxy Polymers, Inc. best selling, favorite product. Visit our FAVORITES - 7 EPOXIES THAT WILL FIX ANYTHING  web page at: epoxyproducts.com/favorites4u.html View other popular one-of-a-kind products.



For the last year or so I had suspected the naphtha to be perhaps the ‘secret ingredient' in ABCD (if it did have a secret performance ingredient). When I tested with naphtha as the sole solvent I found it didn't mix will with the epoxy. Much of it separating out from the epoxy. I solved the separating problem by using a 50-50 mix of naphtha and xylene. However, I also observed that using all xylene gave better and quicker penetration. To my surprise the penetration observed with ABCD was clearly ‘middle of the pack' or less.
 


Isopropyl alcohol is one solvent that can be mixed with water. This suggested that it might be a better solvent in or on damp surfaces. I repeated my tests using damp cardboard and 1 container with alcohol as the sole solvent, one with just xylene and one with a 50-50 mix of xylene and alcohol. I also poured a bit of water on to top of each test cup. Somewhat surprisingly, the xylene only mixture still produced the best penetration. It also managed to incorporate the water I added to the mixture. No free standing water was observed in the cup after the epoxy had gelled. There was free water in the alcohol only test cup.


 



AFFECTS OF LARGE AMOUNTS OF SOLVENTS IN EPOXIES


When a solvent thinned epoxy is spread out as a thin layer or passed through a spray gun, I suspect that most of the solvent is evaporated away before the epoxy sets up. When epoxy and solvent are mixed and allowed to sit in a cup, there is very little evaporation. The epoxy slowly (very slowly) begins to harden into something like Jell-O (tm). Over time it will get a bit harder (like a hard boiled egg) but I have never seen it get rock hard (even with samples months old). The warning here is don't add solvents to epoxies that you want for strength. Solvents will weaken the epoxy but also give it flex.




SET TIMES


As stated above, an epoxy mixture with 65 to 75% solvent takes a long time to set or gel. In my tests above it typically took about 40 hours to gel in the cups. The exception was the ABCD. It took about 80 or 90 hours to gel. Is this a unique attribute of ABCD? I can think of no benefit from a 90 hour pot life vs a 40 hour pot life. Still, perhaps it is somehow improving real world performance.



I set out to try to match the long ABCD pot life. I did this by using as my base epoxy, our Summer Bond epoxy - a solvent free marine epoxy designed for hot weather. In other words, it cures slower than other epoxies so it has a longer pot life in warm weather (actually a longer pot life under all conditions). Because this epoxy starts out with no solvent in it, I added 2 parts solvent to 1 part epoxy. This gave me a final solvent percentage of 66%. It also gave me the 80-90 hour pot life seen with ABCD.
 


CONCLUSIONS


Maximum penetration in penetrating epoxies comes when the solvents comprise 65-75% of the mixture. Common xylene appears to be the best solvent to use. While any epoxy could be thinned and used, we recommend our ESP 155 epoxy (which already contains some solvents, is a 1 to 1 mix and is sold in ½ gal units) mixed with equal amounts of xylene - an easy to do mixture. If one wants the exceptionally long pot life (which doesn't seem to be much of an issue, maybe) similar to ABCD use our warm weather Summer Bond epoxy which is a 3:1 mix and sold in 1 gal units. To every unit of mixed Summer bond epoxy add 2 units of xylene. - Note: summer bond is no longer available (1/2007)



By making your own solvent thinned penetrating epoxy you can save ½ to 2/3 of the cost of purchasing ABCD.


Warming the epoxy resin will decrease its viscosity and improve penetration. So too will warming the surface it is being applied to. As the object cools, the air in it will contract, helping to draw the epoxy into the object.

 

As a 'sealer',' 'primer', or 'under coat for paints or varnishes, epoxies have proven their worth. No special product is needed here. In my opinion, just about any epoxy, thinned or unthinned, will perform this task in a satisfactory manner.



A Warning: In researching this topic I talked with other full time epoxy professionals both inside and outside the marine industry. I was graphically reminded of the health hazards and flammable nature of solvents. Use EXTREME care when working with them in engine areas, confined spaces, and in open flame heated work areas.
 


LEGAL NOTICE: There are federal, state and sometimes county restrictions for the use of solvents. High solvent products are generally illegal throughout the entire USA. The 'fix' by these vendors is to use some 'low end (???)' solvents that are exempt from the regulations. So, instead of a good product, you might just be getting a 'legal' product. For details on VOC (solvent) restrictions see: http://www.epoxyproducts.com/voc.html. Note that if you add solvents to products and thus exceed the VOC regulations in your area, you are technically breaking the law.



More testing of Two Part Penetrating

Epoxy resin systems and their Solvent Content

 


In this new round of testing I used softly packed sand for the 'testing' medium as it had uniform porosity that was repeatable sample after sample.

 

Four different test epoxies were used, a uniform amount of each poured upon the sand surface. After the epoxy had set, I measured the weight of each 'sand lump' as an indicator or penetration.


Sample 1 - commercial penetrating epoxy with solvent level of approximately 70% - (two tests) sand mass 75-80 grams

Sample 2 - ESP 155 penetrating epoxy (solvent level 25%) - sand mass 60-65 grams

Sample 3 -ESP 155 with additional solvent (approx. 70% solvent) - sand mass 70-75 grams

Sample 4 - Low V (low viscosity) solvent free epoxy - sand mass 50 grams

 


NOTES: the large sand masses of samples 1 and 3 (low epoxy %) easily broke apart. The higher epoxy % masses did not break apart easily.

 

CONCLUSIONS: more solvent equals more penetration, but less strength.


"Penetrating/priming" Products offered by Progressive Epoxy Polymers, Inc.


LOW V™ (thin, solvent free epoxy - add solvent to this to make a penetrating or priming epoxy) - Click Here

ESP 155™ (our own clear primer epoxy with approx. 25% solvent - add more solvent for an easy penetrating epoxy) - Click Here


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