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What is PU3000?

Jul 18 2017 - 14:22 PM

What is PU3000?

WATERPROOF AND SUN SHELTER: The inner tent use waterproof 190T, waterproof rating to PU3000. UV protection layer, UV protection grade 50+. The flysheet tent use waterproof 210T, waterproof rating to PU2000. UV protection layer, UV protection grade 50+.Both of 2 Tent protect you from UV damage in the summer and keep you and your equipment's dry in the rainy day.
MULTIFUNCTION: Inner and Outer Tent superpose together (suitable for the camping rainy day). Inner tent also can be taken out and with using the 3 shock corded fiberglass poles Tent Pole it can be realized alone, at least accommodate 2-3 adults. Rainfly can be used as a wayside pavilion with the groundsheet, fishing awning, canopy, can accommodate at least 3 adults. The tent is definitely the first choice for couples and family trips.

Polyurethane coated fabric has coating of PU on one side of the fabric, as with an acrylic coating. The PU coating tends to be a bit thicker than an acrylic coating and looks slightly duller. It appears that PU coatings are more expensive in practice - although this may be influenced by the obvious fact that a thicker layer needs more polymer. Normal use of a PU-coated fabric puts the coated side on the 'inside' and leaves the fabric on the outside. This protects the PU coating from UV and abrasion, but it also means that any rain can soak into the exposed fibers on the uncoated, exterior side. This makes drying a long process, as that water can only dry out of those fibers as fast as it can evaporate from the fabric surface. Since it usually rains only on cloudy days the sun won't be helping that drying process, and as a result you get to carry a water-sodden parka or tent on your back all day, or at least until you can stop hiking long enough to dry it out.

Some PU-coated nylon fabrics have a Durable Water-Repellent coating (DWR) on the fabric. In principle this should stop the fabric from absorbing any water: the water should bead up and roll off just as some pretty catalogues illustrate. But what those catalogues don't tell you is that the DWR does not last very long out in the open (a year or two), and the DIY versions for home use seem to last even less time. So the fabric gets wet. For a tent this just make it heavier; for a parka it also makes it cold.

What makes the PU-coating of value is the fact that water vapur can slowly diffuse through it, and this makes the fabric 'breathable'. There is more on this under rainwear. Whether this makes much difference in a tent is highly debatable: when it is raining and the surface of the fly is wet, I don't think there is going to be a lot of moisture transmission. You would be much better off ensuring some good ventilation.

For a while there was a very interesting bright orange fabric on the market. Different Australian gear manufacturers tried it out, and it usually got a company name with the word 'titan' or 'titanium' in it. The base fabric is very light nylon and the coating is PU, but the coating is heavily loaded with titanium dioxide (hence the names). The presence of the TiO2 in the PU makes the PU layer very resistant to UV damage. I Believe the fabric was also available in a grey, but how boring! The history of the fabric is amusing. It was developed by Dimension Polyant in America (DP) as a fabric for making very high altitude research balloons for NASA. The PU coating is thoroughly air-tight and is meant to be sealable. (However, some of the first balloons tested near Woomera leaked. Such is life.) Then the marketing manager at DP thought to try selling the fabric to the outdoors industry, and samples were distributed. Tents were made and tested. For an example have a look at my orange winter tent in the DIY, Ultralightweght,My automatic camping tent,and 3 seasons automatic caming tent.pages. It's a really waterproof material, but it didn't stay on the market long because it was soon found to have two serious disadvantages. The first was that the fabric did not have any DWR, and it got wet from condensation on the inside. This was not good. But the second was worse: the thick PU coating went quite stiff in the winter, making the tent hard to roll up. 

There were some fears about cracking at low temperatures as well, although I don't think this would have happened in our snow fields. Anyhow, my orange tents has lasted for many years of hard work. Fascinating stuff.
You need to look after PU-coated fabric. The PU coating itself can absorb water molecules - that's how it 'breathes' after all. The technical term for this behaviour is that the coating is 'hydrophilic' (water loving). But as a result, water can act as a very slow solvent to polyurethane. So if you pack up a wet PU tent for a very long time the PU coating may eventually stick to itself and become one big ball of goo. Actually, it will probably become a big ball of mould first, but that's another matter. I have also seen claims that PU-coated fabric doesn't age very well, and that the coating can peel off as the fabric ages. I have seen PU coating peel off the light nylon throats on packs, but it did take years for this to happen - and an awful lot of hard use too. It seems the problem is that the coating does not normally stick to the fibres in the threads all that well.

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