How does goretex breathe with a PU lining?

Polyurethane can be formed in many ways. It can definitely be made breathable although most gortex alternatives are based on pu so Im surprised real gortex it pu coated

it's not a solid form of PU, is made specially to allow water to permeate through it... the PU membranes have pores in them. although the ones that coat goretex may be more like a matrix that the water works its way through... it may only be permeable to vapour, the gore tex is, if you get liquid contacting gore tex it won't go through unless it is in vapour form where the molecues are small enough to permeate the membrane. gore tex is chemically different from PU, ePTFE, it gets clogged by body oils by default the PU is put over it to stop it from getting clogged, PU is more resistant to body oils and easier to clean. although some of the latest versions of Gore tex such as pro have been abe to remove the PU layer and still work and have an undisclosed sandwich of chemicals in between two layers of gore tex event is epfte and treated in an undisclosed way to reduce oil build up, but it still needs to be washed regularly to keep the buildup down...

Gore-tex is a membrane in itself. PTFE PolyTetraFlouroEthylene. It is used as a layer and i'm dubious that anyone combines it with a PU coating. A PU coating is generally used to make a cheaper jacket that doesn't have a breathable membrane. The most accessible form of gore-tex is plumbers tape. Take a look. It is a thin white membrane with countless microscopic pores. Each pore is like twenty thousand times smaller than a drop of water. That allows the waterproofabilty. Water vapour on the other hand, which is what you give off initially as sweat, is a gas and the molecules are smaller than the pores. Temperature differential is what makes it work. That is the difference between the temperature inside the jacket and the ambient temperature outside. The greater the difference, the higher the rate of breathability. This can be demonstrated by wearing the jacket when working out. Trap the heat in the jacket by doing up the cuffs and neck and hem drawcord. Try to create the greatest temperature differential. The inside of a lot of gore jackets do suggest best performance is in lower temperatures. Ideally it would be zero outside and 37 inside. Give it a little time and you will dry inside. The DWR on the outside is relevant because it allows water to bead and give room for more to escape. A reason why the wind being present will help. A worn, heavily creased or frequently washed jacket will wet out on the outside and therefore be less effective. When it comes to windstopper etc, they stretch the membrane further to expand the pores. It decreases waterproofability but increases breathability. As for body oils etc, they do block the pores and require the item to be washed. The nature of gore-tex and how it works suggests combining it with a PU coating would be pointless.

I have seen a couple of jackets saying they have pu over gortex. The gortex membrane isnt very robust and they often put something over it, it lasts longer. The first gortex coats were a single layer or gortex on a face fabric and were the best performing of the lot but they failed quite quickly.These were 2 layer coats. Then they put a second liner inside the coat which protected the gortex but were heavy and didnt breath that well.These were the first 3 layer coats. Then they tried a very fine fabric bonded to the inside of the gortex as a 3 layer and they printed a raised pattern onto the gortex to allow an air gap. These are the 2.5 layer coats. I suspect this is how the pu is being used. Also just to confuse most alternate fabrics use a pu membrane instead of gortex. It can perform as well but isnt as durable. Macpacs Reflex and Pategonias h2no are PU based fabrics

2.5 layr arent gore tex they are a breathable PU layer with a durable pu layer over the top. goretex is completely covered by either PU or a knitted or woven protective layer over the top

from https://www.paddypallin.com.au/blog/all-about-waterproof-fabrics/ GORE-TEX Paclite: Pacite is ideal for exactly what the name suggests, packing light. This fabric is a 2.5 layer construction and whilst it’s waterproof ratings are solid, it’s more suited to travel and urban wet-weather gear than strenuous rough outdoor activities. The Marmot Minimalist jacket/pant and Arc’teryx Women’s Beta SL jacket all employ Paclite & are perfect for your next trip enjoying the sights, sounds and flavours of Europe for example. That website also has a lot of info on this entire subject

the brown layer isnt gore tex, its the PU layer, goretex is white, they call it 2.5 but 2.5 is supposed to be a pattern partially covering the membrane... they call 3 layer the material that has knitted nylon tricot over the top of it... its gore tex distorting what 2.5 layer is

Gore invented it they can set how its used (or they could until the patent ran out

So would it be right to say that goretex is only as breathable as the PU coating?