Minicell T-200 (Crosslinked EVA)

Another note – while neither Foam By Mail nor Gossamer Gear list a measured and specified R-Value (GG only stating that its 1/4″ pads having approximately R=1), the Alveolit, which FBM lists Minicell T200 as being very similar too (maybe nearly identical), does list a thermal resistance in it’s specs, albeit for 2mm and 3mm thicknesses. Extrapolating the values for 1/4″ thickness results in a R value of a little more than 1 (1.063), so the GG claim seems reasonable. A 1/4″x20″x72″ section should weigh  6.67oz, so not a bad penalty if you are looking to make your sleep system more robust (i.e. make sure you aren’t sleeping on frozen ground if your  air pad goes flat!)

https://www.floorsalesonline.com/files/alveolit-underlay.pdf

Thermal resistance at 10°C, per  ISO 8301 (2mm thk):  0.059 sqm-K/W

PM

I did a simple compression and recovery test on all 2lb density CCF available from this vendor, including Minicell 200. Only one stood out with a faster recovery: the cross-linked polyethylene.

The benchmark piece, a genuine Evazote from Flex-Tech, far outperformed all the others. The test consisted of pinching the foam with a 1″ binder clip for 24 hrs and timing the recovery of the resulting impression. Some samples have not fully recovered yet here 4 months later, lol.

Hey @roamer, what real world situation does your binder clip test represent? I understand what you are saying, but let me make a comparison – what you are saying is that your Toyota Corolla family car performed poorly when you entered it in the Indy 500. A bit hyperbolic, yes, but I do not see any situation involving me laying on foam or carrying a pack that would be well-represented by your paper clip test. It puts an immense pressure on a very small surface area.

Is Evazote a better material? Likely. If you can help me find a vendor willing to sell me full sheets for my MYOG use for a similar price, I would love to purchase a bit. I don’t want to pay a markup to Gossamer Gear for a piece that is less than 1/2 the size for the same price, with no real world performance differences.

It puts an immense pressure on a very small surface area.
Well, yes, but it is a good test for recovery. As noted, some foams just collapse under load and stay that way.

Cheers

The manufacture lists both compression strength and compression set of the material. All it would take is some basic calculations to understand whether your use case was going to exceed these.

For my purposes assume a 200lb man standing on a Minicell T200 pad. Represent the standing with a 12″x12″ distributed area, or about the area taken up by his shoes. Compression strength for Minicell T200 is 4lb/sqin for 25% deflection, and 11lb/sqin for 25% deflection. The man standing on this pad in this example exerts 1.389lb/sqin. Compression on these foams is not linear, but I would suspect the compression in this load case to be between 10-15% deflection. I suspect 50% is the max deflection it would take. I’m unsure what the paper clip would exert over its thin interface with the foam, but it is likely to be much higher, causing the permanent damage which has been summarized previously. I don’t think the paperclip test gives me any reason to believe the foam is not usable for a vast majority of ways it might be used in the backpacking industry. I think we are at this point looking for poor ways to burn hard-earned cash. But obviously Evazote exists, and people buy it (at a premium).

Edit: MLD sells Evazote. Up to 1/4′”x40″x80″ (13.2oz, or about 1.8lb/cuft, R~0.8) for $66+tax+shipping. more than double the cost compared to the Minicell.

causing the permanent damage which has been summarized previously
A very good point which I had overlooked. I will have to withdraw my previous comments.
Cheers

Of course the binder clip test is not ideal. But it were easy and compact; and the only one I know of doing a comparison of the all the CF foams available from arguably the most attractive online vendor.

As I mentioned one recovered faster, the cross linked polyethylene. I also placed a weighted cement block on this foam and the runner up from the clip test and observed similar behavior .

Perhaps more significantly, my sample of cross linked polyethylene is much lighter than T200. The overall lightest were Volara and regular polyethylene.

In appearance the cross linked polyethylene and T200 are indistinguishable, although the latter is more difficult to move into place inside hipbelts and shoulder straps, possibly due to surface friction. None of them are as easy to work with as regular polyethylene, a ubiquitous but visually unattractive foam (akin to blue Walmart foam) used by at least one major cottage pack maker and readily available from MYOG suppliers.

Finally cross linked polyethylene is slightly cheaper than T200.

Some types of minicell are used in paddling industry for padding inside of kayaks and for roof mounting on automobiles.

Is the product sometimes referred to as plastazote or zotefoam  cross-linked polyethylene?

Why would evazote be preferred as a ground pad to plastazote and what is the ‘name’ for evazote?

Trying to learn something not challenging.

How does minicell T-200 compare to the 2 above in terms of weight and insulation?

What does the term 2lb. or 3lb or 4lb refer to with cross-linked polyethylene?  Weight of a cubic foot?

Thanks!

Is the product sometimes referred to as plastazote or zotefoam  cross-linked polyethylene?

Why would evazote be preferred as a ground pad to plastazote and what is the ‘name’ for evazote?

Zotefoam – a brand, or company that makes foam.

Plastazote – Zotefoam’s trade name for cross-linked polyethylene foam

Evazote – Zotefoam’s trade name for cross-linked EVA foam

How does minicell T-200 compare to the 2 above in terms of weight and insulation?

Minicell T-200 was compared to Alveolit foam, interms of insulation. It comes in multiple densities. I am looking particularly at 2lb/cu.ft. At 1/4″ thick, R=~1.02, so it is comparable (on paper) to the Zotefoam offerings.

What does the term 2lb. or 3lb or 4lb refer to with cross-linked polyethylene?  Weight of a cubic foot?

Yes, weight per cubic foot.

By all accounts, cross-linked PE (Plastazote & Minicell L200) and cross-linked EVA (Evazote & Minicell T200) demonstrate similar insulating properties, but have slightly different physical characteristics. Typically, EVA exhibits a bit more “rubbery” properties, being a little more spongey and and is typically a little more resilient (bounce back, return to it’s shape)  when kept within it’s performance spec limits. PE is generally a little stiffer, and so, in my experience, folding it and compressing it takes a little longer for it to recover. This takes the form of creasing staying longer after folding/unfolding (i.e. removing from a frameless pack if used as a “frame”). Everyone’s experience and use cases are going to be a little unique based on where they store it, how they use it in the field.

Some EVA foam contains Formamide. EU has a ban in place for toys of it.

Thanks Michael. I have a 1/2 piece of cross-linked PE that I use as a pack back-pad and sit pad and as you noted it doesn’t ‘recover’ rapidly at all, but then I’m not folding it; though I did ‘hinge’ it at the bottom so it covers the bottom of the pack.

2lb/cu.ft is 2lb/cu.ft so if the insulation properties are @ the same….

But are they?

Does the rebound or resilience That implies a greater tendency to compress and then rebound from the compression have an effect on the insulation by a tendency to be more compressed when weight like the pointy hips of a body is applied?

I’ve seen some pretty spongy yoga mats and blue foam pads and the old ensolite from back in the early 70’s  (when it seemed like a miracle). That compression reduces the insulation. (and the comfort)

The cross-linked PE  might not recover as efficiently but it also might not compress as easily and so might stay warmer?

If the weight of a body doesn’t squish it right down And the idea is to avoid heat loss sinking into a cold ground rather than leaking into cold air then a stiffer pad might work better? Plus you could create an ‘accordion’ type pad if the idea is protection from heat loss due to compression at point of contact with a heat sink and it would also work as a layer to protect from sharp objects.

I’m probably over-thinking it. The things we do to save a gram or 2!

All the things you say are on point – for insulation properties, we can make some assumptions about about it based on the chemical makeup, process, and physical properties, but ultimately, if it is not tested and reported according to some standard, we cannot know without doing a standard testing ourselves. For me, in this case, it is pretty low risk/not critical to my survival, so I am ok with my assumptions.

Regarding the issue with the possibility of compression under hip/etc load more for one foam or the other, the compression strengths are actually listed for most foams, so that is easily compared between products. Minicell L200 does have a higher compression strength than the T200, 7psi vs 4psi to 25% deflection. L200 has a better compression set value as well, that is to say it recovers better after being compressed according to the standardized test. T200 has slightly better tear resistance and tensile strength numbers. So we have some tradeoffs that would need to be evaluated further, i.e. would the increased deflection at the hips by T200 offset the overall thermal performance in a detrimental way? I would guess no, since these are localized spots with a relatively low surface area – this assuming you plan to use only a CCF pad, and no air pad. Would the increased stiffness of the L200 produce a less comfortable sleep for someone only using a CCF pad? That is very subjective and unfortunately you’d have to experiment, or trust a company who purports to have done the research and made the decision to use one type over the other. If using under an air pad, the differences are likely to be very minimal, and I’ll take the increased tear resistance and tensile strength and relative comfort (in my opinion, of course!) of the T200 over the L200, compression set be damned!

YMMV, of course.

Some EVA foam contains Formamide. EU has a ban in place for toys of it.

thanks for the info, I’ve inquired with FBM about the T200, will see what they say.

https://www.hellonaturalliving.com/the-lowdown-on-eva-and-eva-foam-safety/

That site has a level-headed review on the topic – I’d say it is a low risk for us, maybe more of a problem for children who may be inclined to eat the foam, idk.

Yes, no big red flags about harm to adults. We don’t eat it. Just nice if I have a choice to use the less problematic material.

I have been using Zote Foams for years as well as Volara, as cushioning in cases for oxygen tanks and as sleeping pads. Mostly Plastizote. The EVA is more durable under foot- say for shoes etc. The Plastizote is slightly lighter and higher R value for the weight. As sleeping pads  go, there doesn’t seem to be a noticeable difference between the two in real life use.

If they were sliced very thin, there might be a tear strength difference that could be important depending on use. I do not know which would be stronger for that.

What kills you in cost for foam is the shipping. I was selling 1/2″ full length  two person pads. Suddenly last year, when Trump was messing with the the post office, they started back billing me an extra $50 after I had shipped thru them. I had to quit offering that large a chunk of foam.

Hey Dave, thanks for your real world experience, I appreciate that.

As for your complaint about the shipping costs, that is why I started this thread! I’m frugal (it is the only way to afford owning a home in Cali!) so I wanted to see if there were any others that might be wanting foam, but didn’t want to buy a whole sheet, or an overpriced partial. I am offering to help get MYOGers exactly what they need without having to deal without having to deal with getting gouged by shipping or a middleman, which I am effectively volunteering to be for this in order to make my MYOG projects more efficient, both financially and material stock-wise.

I’m in if you can put something together! Thanks for all the info. This has been a very informative thread.

BTW while we’re on this subject, has anyone ever tried the polyethylene foam flooring underlayment as a ground pad. Specs at 2mm with vapor barrier but in my hand with a tape measure appears more like 1/8th.

2′ x 4′ weighs 2.6 oz. Wouldn’t want to rely on it as a sleeping pad but might make a usable ground pad/vapor barrier.

And then there’s the thin foam type stuff flatscreen tv’s are packaged in. That stuff is really thin and really light. Maybe lighter than polycryo. Make a nice gear/clothing pad? Why not?

OK not lighter. Polycryo 75 mil is 1.725 grams per foot sq.

polycryo 100 mil is 2.16 grams per foot sq.

The TV wrap foam is 2.31 grams per foot sq.

The piece of tv wrap I saved is 38″ x 52.5″ and weighs 32 grams. Bulkier too. about twice. Sure lays nice and feels nice. Good ‘hand’ as they say about fabrics. And otoh you could fold it up and make a sit pad or small pillow.

I have some of the 2mm foam you are talking about, I use it as protection for my AXL pad. It is the kind of foam you get from Grainger on a huge roll; we use it to protect product at work.   It adds a little insulation, but it is not warm by any stretch of the imagination. I froze my buns off with that setup on a 30deg night over New Year’s Eve. It is good as pad protection though, not very durable. It was free to me though, as it was just leftovers at work headed to the trash. It has held its own in my pack the past   6 months.

the tv wrap is pretty delicate, if we are thinking of the same stuff, but yeah, it is softer, the bubbles are finer.

I have experience with the 2lb cross linked polyethylene foam from them.

I used it in shoulder straps for a lightweight backpack carrying less than 30lbs. During a single through hike (3 months) I noticed significant compression and lack of resiliency. I would not use this foam again for this purpose and was actually planning on trying out the t200 eva foam next but up to 4lb instead of 2.

Switching to a higher density might be a good choice for pack straps.

FBM got back to me regarding the use of formamide. It looks like it is used in the process for the EVA. I’d suspect all EVA production uses it, and the products that advertise the absence of the chemical are just further along in producing testing regimens to analyze the finished products. Most of this is being driven by EU REACH compliance. Sekisui, who apparently manufactures the Minicel (FBM is just a distributor) is working on a test procedure, presumably so they can once again offer this product legally in the European market, as the finished product must contain less than 0.1% of the chemicals on the REACH list, as best as I can tell. Anyway, just one more reason for me to trust buying products from FBM, as they were responsive and provided as much information as they seem to be able to.

Our manufacturer did reach back out and formamide is used on our EVA Minicel foam.

 

On December 19, 2012 the ECHA updated the Candidate List of SVHC’s which at that time contained 138 substances.At that time Diazene-1,2-dicarboxamide (C,C’-azodi(formamide)), Azodicarbonamide, CAS # 123-77-3, was added to it’s candidate list of “Substances of Very High Concern” (SVHC). The maximum threshold concentration level is for this material 0.1%. Azodicarbonamide is used as a foaming agent in YOUNGBO Chemical’ Eplion, Artilon, Youngboard and Minicel manufacturing process. The process is designed to completely activate the azodicarbonamide. Any remaining, un-activated foaming agent is minimal in the Eplion, Artilon, Youngboard and Minicel. Further, there is no established evaluation test method to measure the residual concentration. Our parent company, Sekisui Chemical, is working on preparing a quantitative analysis of this residual substance, however such analysis will require an extended amount of time to develop. Once the test method has been established, our products will be tested for compliance, and we will inform you of any issues related to SVHC compliance.