I have read polypropylene underwear, also known as "Merkalon" loses it's sweat / moisture wicking abilities after it has been washed several / a few times.

This was the main reason given why polyester thermal underwear is superior.

Does anyone have experience / knowledge / an opinion on this?

Can't answer your question but Merkalon was invented by an Italian who won the Nobel Chemistry Prize for the development .They are putting up a plant here in WVA to make it.I would assume from the type of special polypropylene that the effect is in the fiber not a coating. Do they give special washing instructions ? Some of the water repellant fiber coating are adversely effectd by detergents.

Mete,

I was wondering too. My initial reaction is it is some sort of marketing ploy by makers of polyester 'thermals'. I was unaware man made fibre thermal underwear had any coating.

Looking at the washing instruction labels inside my Helly Hansen brand Merkalon thermals, all it states is NO ironing, No tumble drying, Max temp 60 degrees C, NO TRIANGLE - BLEACH??

There is a capital P inside a circle, which I think means dry cleaning ok?. No sure about this. There is also a a dot centred within a circle, which is enclosed by a square. I think this means machine washing ok. However, an older make of merkalon thermal underwaer has a cross through this square/circle/dot symbol.

I would have thought dry cleaning chemicals would have 'eatem' the plastic filaments of the 'cloth'.

I really am not very domesticated. Until I left home to attend university, I believed in the washing machine fairy!

Google "fabric cleaning symbols" you'll find lots of info .I wish I knew more about textile chemistry but I do know many chemicals are used for many reasons.Fabric softeners are noted for causing allergies ,other chemicals can cause allergies too !

The beauty of polypropylene is that it doesn't asorb moisture at all. It is a plastic. That means the sweat goes completely through it and is trapped in whatever is outside the poly underwear. You stay dry, and warmer.
I have worn poly underwear in single digit temps while sweating like a pig, then stopped and glassed. I never did get cold. It is good stuff.

I have a Merkalon "headover"/ neckwarmer which I've had for something like 5 years, and it is possibly my favourite bit of hunting clothing...Over that period its been washed many times and I can't detect any change other than it becoming softer and more comfortable.

I also have a sleeping bag liner made of the same stuff and while its not be used any where near as much, it's still been washed a fair few times with no obvious ill effects.

Regards,

Pete

Thank you for all the feedback.

Mete, I googled washing instructions and then wandered like a free electron etc.

I did not know there was at least two types of sweat. One is much more icky than the first and contains fats plus proteins. Yuck!

I traced the origin of the statement, prompting my question. It is in Chris Batin's book on hunting in Alaska.

While I have reda that polyester underwear is a bit better / easier to wash, and less 'reactive' around / exposed to open fires, I cannot find anything to support the losing wicking ability with repeated washing. I understand that synthetic sleeping bags, and to a lesser extent fibre pile fleece jackets, lose their thermal properties with repeated washing. However, I believe this is due to physical break down of the hollow core filaments in synthetic sleeping bags and compression / squashing / flattening of the fibre pile fleece.

As a result of these mechanisms, less air is 'trapped' within the covering, between layers of material. Since air is a good insulator - it does not conduct heat very well, this reduces the mateials thermal retention / insulation properties.

Ho, hum. I am not really that much wiser, but I do not think it is a 'real' problem with Merkalon garments. Certainly, my Helly Hansen thermals are warm as toast. In fact the Merino wool / merkalon mixture thermals are a little too warm with layered clothing for hind culling. As I found out last week!

Does anyone have first hand, practical experience with the Snugpak 2nd Skinz polyester and Sub Zero Factor 1 Tactel 'fabric' thermal underwear?

......Polypropalene long under wear was a mainstay in on the coast here until Thermax came along ........What causes propalene to loose its wicking and warming ability is being washed and dried on too warm or hot a temp......The same will ruin the polyesters also.but to a much lesser degree .........I,ve been wearing synthetic uw for 7-8 months a year for the past 28 years and I,ve come to a few conclusions .......The polyesters are the best ...........If all you can get is Ploartec 100 ....you will be nice and warm .....I have long johns that I have worn for more than 1500 days and they still work relatively well ....The propelene gets scratchy sooner than the polyester and once they get scratchy they are only about half as efficent as when soft...Propelene absorbs oil ....So when you perspire and oil comes off your skin it gets absorbed by the garmet,,but it won,t absorb enough water , which carries the detergent to wash the oil ,,,which carries the odor ect. away .............Polyester is completely washable ........For me polyester causes less ,, fungus amongus ,, ,,,,,,I sweat more than anyone that I know,,,..Polartec and Comfortrele are my 2 favorite fabrics ......I like the new slippery long johns as they make moveing around easier ...But I,m not so keen on the new compression fit stuff .......Cabela,s Seirra Tradeing Post , Ect ect ...carry very good selections for reasonable prices ......The Capilene material works ok but I prefer not to buy new Patagonia .......Capilene is an acid rinsed poly propalene ,, the mild acid fuzzes the thread and makes so it can be washed clean in a washing machine better ........It still gets to stinkin after a while ......Hope this helps ...

I wash all this polypro "stuff" in Woolite with cold water. Then I run it through another wash cycle with no "soap", so if I wear it for several days in a row it does not irritate my skin.

Thank uou all for the information.

Gumboot458 - what is the problem with the compression fit thermal under wear?

I thought close fitting clothes would be better at trapping a layer of still air against the skin. It is the air, which is a poor heat transfer medium: ccr, which enables retention of body heat.