Sika Post Mix Expanding Foam?

[rharshberger]

Sika Post Mix is a 2-part expanding polyurethane foam, pretty sure its similar/same as the expanding foam we use in fin cans and nose cones. According to the manufacturer it weighs 2.06lbs/.7cubic feet (based on package weight and area filled per package) or as the other manufacturers say 3lb density. It looks like it might be useable for the same things we use the GLR, Wildman, US Composites, TAP plastics, and Fiberglass Supply expanding foams for.

My question is: has anybody used this product? It is locally available to me at Lowe's and Home Depot for about $12 per bag. I am tempted to go buy a bag empty the two compartments into separate containers and do a few tests to see what the expansion ratio and if its a 50/50 mix.

https://www.homedepot.com/p/Sika-33-fl-oz-Fence-Post-Mix-483503/205671519

 

[Chad]

Lol I never would have thought foam could be used for fence posts.

I need some foam to fill a mandrel for fiberglassing tubes. Will give this a try today and report back how it works out.

EDIT: just noticed this too, a little more convenient since the parts are already separated and not in the same bag https://www.homedepot.com/p/Secure-...ing-Foam-White-1-Post-Kit-SS-SP-824/206497517

 

[rharshberger]

Lol I never would have thought foam could be used for fence posts.

I need some foam to fill a mandrel for fiberglassing tubes. Will give this a try today and report back how it works out.

EDIT: just noticed this too, a little more convenient since the parts are already separated and not in the same bag https://www.homedepot.com/p/Secure-...ing-Foam-White-1-Post-Kit-SS-SP-824/206497517

The foam from the link you posted is not available in store for me. But the Sika product is, I got a feeling this stuff will work.

 

[BABAR]

If you use Fence Post filler and the rocket lawn darts, will that make it harder to pull out?

 

[rharshberger]

If you use Fence Post filler and the rocket lawn darts, will that make it harder to pull out?

If its a fiberglass rocket just attach the fence wire to it a voila you have a new section of fence, however placing post by the ballistic impact method may not result in a very straight fence line. [emoji3]

 

[rharshberger]

Here is the partial test portion of the package of Sika Flex Post Mix 2 part foam.

The package purchased from Lowes, it is double packaged inside a ziplock bag with handles.


Mix De-bagged
there is slightly less than 500ml of Part A (marked on bag in lower corner A), and slightly more than 500ml of part B. The part A component is a honey like consisitency with a gray-green tint, the Part B component is what appear to be nearly identical in color to Gorilla Brand Polyurethane glue and the consistency is about that of polyurethane paint (water like). The difference in volume may have had to do with the viscosity difference between the two parts (guess on my part).


Basing my assumption on a 50/50 mix due to the approximate equal volume, I drew up 3ml of each part into individual syringes (seen below), the receptacle is a 3oz plastic Dixie type cup (I believe the brand was actually Solo) according to the marking on bottom of cup it is 88ml in volume. Both components were squirted into cup and the skewer was used to stir components for approximately 30 seconds.



Picture below was at about 10 seconds after stirring stopped.


About 40 seconds after stirring.



About 70 seconds after stirring.



100 seconds.



And lastly about 180 seconds after stirring (time based on initial estimation and time/date stamps from original photos).



After about 30 minutes after mixing the surface was hard and non-tacky so I decided to cut it open with a Zona Razor Saw. The interior if fully cured and hard. If the cup was 88ml and I put 6ml of product into the expansion ratio once fully expanded is something over 15:1 (my guess is closer to 20:1), the 20:1 ratio would tally with the product data sheet of .7 cu ft (20000cc) and a density around 3lbs per cu ft. (weight of 1000ml total of two components was 1090.3g). Sorry for mixing units of measurement and I am sure my math is pretty much about as close as horseshoes hand grenades and nuclear bombs but it should be approximate.

The product appears and feels to be standard 2 part foam and just for fun I did a "sticky" test, and as usual the warning of "don't get this stuff on anything you like" is accurate, its very sticky until cured. Once cured I could push very hard with my thumb tip until I couldn't push into the foam any more and the impression was about 3/32" deep.

 

[Chad]

Got the same stuff today too. Yeah, very sticky, heh hard to keep the kids from messing with it.

 

[gcanroc]

Cost wise I think this is a good substitute, but could you store the unused portion of the "post mix" for future use?? It seems like product is meant to be used all at once.

Geoff

 

[rharshberger]

Yes..yes you can. I store the two parts in the "disposable" Ziploc brand screw top quart containers, and for measuring a pair of 35ml syringes labelled A and B ( containers and syringes visible in multiple photos). I just used some of the foam from this thread to do a nosecone about a month ago, worked fine.

 

[rharshberger]

Foamed a 3D printed 8" diameter nosecone with this stuff today.

 

[bjphoenix]

Lol I never would have thought foam could be used for fence posts.

It is useful for a number of construction tasks. It isn't as strong as concrete but it is stronger than the surrounding soil. It is good for placing posts and poles in places where it isn't convenient to bring in concrete.
You could always turn the tables and use concrete in your nose cones, but it will weigh a little bit more. (You know I'm kidding here.) There is a such thing as "foamed" concrete which can get you down to near 20% of the density of normal concrete. This might still be a bit more dense than what you want.

 

[rharshberger]

Just so others are aware, todays batch used was my second batch, even storing it in the ziploc screw lid containers the stuff eventually goes bad and it has been 3 years since I started this thread. I don't use enough foam to justify spending the kind of money wanted by our rocketry vendors when I am only going to use about half or less before the product goes bad.

 

[prfesser]

The isocyanate part of this expanding foam will eventually go bad, as I discovered yesterday when I attempted to use it for a fin can. A metal container is less permeable to moisture than the PETE bottle I used (that once held cream) and would be better for longer storage. Regardless, don't count on using it for more than a couple of months.

Best -- Terry

 

[KenECoyote]

Sorry to froth up this topic , but "expanding" on it a bit more , does adding water change the density like it does for PML 2 part foam?

Given how hard (and expensive) it currently is to find my usual PML 2 part foam, I found this post to be extremely helpful and much appreciated!

It is definitely great for use in nose cones as is, but I was wondering about decreasing the density with water in case I want to use it for other applications or less nose weight.

 

[cwbullet]

Sorry to froth up this topic , but "expanding" on it a bit more , does adding water change the density like it does for PML 2 part foam?

Given how hard (and expensive) it currently is to find my usual PML 2 part foam, I found this post to be extremely helpful and much appreciated!

It is definitely great for use in nose cones as is, but I was wondering about decreasing the density with water in case I want to use it for other applications or less nose weight.

I can’t find anything online, but it should based on the fact that it is reportedly the same type of foam.

Sounds like a time for an experiment.

 

[prfesser]

Water added should cause any 2-part expanding foam to expand more. The "expanding" reaction is from water that's already in the mix. Water reacts with the isocyanate part, forming CO2. More water = more CO2. Water has a very low equivalent weight so it doesn't take much water to make a pretty big difference in expansion.

 

[KenECoyote]

I can’t find anything online, but it should based on the fact that it is reportedly the same type of foam.

Sounds like a time for an experiment.

I actually bought a package 2 days ago and plan to test it after finding suitable containers to keep it in after opening the bags.

Water added should cause any 2-part expanding foam to expand more. The "expanding" reaction is from water that's already in the mix. Water reacts with the isocyanate part, forming CO2. More water = more CO2. Water has a very low equivalent weight so it doesn't take much water to make a pretty big difference in expansion.

Thanks prfesser! I suspected as much, but hadn't looked into the formulas. It is surprising that they would have a post hole filler that is very reactive with water (when adding into the hole), however I'm guessing it's less reactive than if added when you mix it in.

 

[prfesser]

I actually bought a package 2 days ago and plan to test it after finding suitable containers to keep it in after opening the bags.

Thanks prfesser! I suspected as much, but hadn't looked into the formulas. It is surprising that they would have a post hole filler that is very reactive with water (when adding into the hole), however I'm guessing it's less reactive than if added when you mix it in.

Glass for storage is better than plastic, though it should last a fair time even in plastic. Old liquor bottles? Geniece drinks some kombucha(?) stuff that comes in pint glass bottles---perfect.

If memory serves there was an excess of the isocyanate part in the post-hole-filler that I tested a good while back. Possibly that's to react with the water on the surface of the hole, I dunno. I *do* know that the mix I ended up using to fill our own post hole is still solid after over a year in place, with the top exposed to the elements. And after being (lightly) struck by a truck's sideview mirror or something.

 

[rharshberger]

Glass for storage is better than plastic, though it should last a fair time even in plastic. Old liquor bottles? Geniece drinks some kombucha(?) stuff that comes in pint glass bottles---perfect.

If memory serves there was an excess of the isocyanate part in the post-hole-filler that I tested a good while back. Possibly that's to react with the water on the surface of the hole, I dunno. I *do* know that the mix I ended up using to fill our own post hole is still solid after over a year in place, with the top exposed to the elements. And after being (lightly) struck by a truck's sideview mirror or something.

The "excess" of one part isnt all that much iirc. The one picture in post #6 demonstrates that its probably 3-5% by volume, I guess I need to acquire a better measuring device and get exact numbers. I have yet to use all the product before it starts to crystalize and I end up just mixing it up and pouring onto a piece of cardboard to later put in the trash.

 

[KenECoyote]

Tonight I tested small batches of just over a teaspoon of each mixed with and without water.

The spoon is a common plastic soup spoon often given with takeout food.



I also tried adding about 1/2 tsp of water and the mix did NOT like it lol


So this looks great for my use!

Much Thanks @rharshberger & @prfesser for the suggestion!

 

[KenECoyote]

I ended up emptying the bags into quart sized plastic soup containers (you get with takeout) since I had them on hand and they're obviously waterproof.

It was also much easier to empty the bags into them and I figured this storage would be fine for me given I plan to use it up before humid weather returns.

 

[KenECoyote]

Update:
I tested the firmness of both batches with an unscientific press of my index finger. The straight mix was very firm and only yielded a bit; however, the lower density one crumbled a bit too much for my taste.

I then did drop tests of a heavy screwdriver from 6" and 12" and the straight batch stood up well.

(Water added one on the right.)

Straight close up:


Water added close up:


I do fully understand that lowering the density by adding water also means less stength; however I thought it would be proportional and instead (to me at least), it feels like it got twice as weak when volume was increased between about a quarter to a third.

The water added batch feels about as firm as pork rinds.

 

[prfesser]

FWIW a little extra of the isocyanate part to the water-added stuff---wild guess, about 20 times as much as the water that was added---may give a stronger foam. Water uses up some of the isocyanate. Of course the fact that it's a lighter foam makes it weaker too.

 

[BABAR]

The water added batch feels about as firm as pork rinds.

sooooo……more filling, tastes bad?