“For those who know about siloxane tapes, the curing time is commercially unacceptable”
Interesting. Thanks for this. Myself I prefer seam sealing because it is applied externally so it stops water from soaking into the seams, whereas internal seam tape only stops water at the last minute before it soaks all the way through. External seam tape that adheres well would be fine, but is typically unsightly. From commercial standpoint I see why PU tapes are appealing (many users don’t want to seam tape/seal), and then from a user standpoint I’d likely just seam seal. Do you find there is an advantage this siloxane tape over seam sealing?
“….both nylon and poly have high UV resistance with poly having an edge there. Not usually a concern though.”
I think it’s too generous to refer to nylon’s UV resistance as high, and polyesters edge as “slight”. I would characterize nylon’s UV resistance as “poor” and polyester as “outstanding” with the difference being “massive”. Or in the words of MoonLight tents, polyester’s UV resistance is “better than nylon by a long shot”.
Here’s a recent (2013) scientific article that compares the effects of UV exposure on the tensile strength of nylon 6,6 vs polyester:
The effect of UV degradation on toughness of nylon 66/polyester woven fabrics
To investigate this, they made custom fabrics with nylon as the warp thread and polyester as the weft. Then they exposed those samples to UV and tested the tensile strength in warp and weft. The amount of UV exposure might not be relevant to real world conditions, but since the nylon and poly are being exposed equally, it gives insight into their relative degradation.
First, here are the results for nylon:

We see that their brand new nylon has a tensile strength of 1600 N, and that drops sharply with UV exposure so it’s down to 600 N after 14 hours and a mere 250 N after 28 hours. So when exposed to these conditions, nylon loses 85% of its strength. You can see it is also becoming brittle, as its stretch at the failure point is radically reduced from 30mm to 4mm.
Now here are the results for polyester:

The polyester actually has a higher initial tensile strength than nylon at 2200 N (which isn’t that surprising because these fabrics are more similar than everyone gives poly credit for) but let’s ignore this because perhaps they used a slightly thicker or better polyester or something. The main take away is the polyester actually gets stronger with UV exposure. It measures 2200 N initially and then 2400 N after 28 hours of exposure for a 10% gain. So nylon lost 85%, while polyester gains 10%. Thus you were to start off with nylon and polyester at equal strength, the polyester would wind up about 8x stronger after being exposed to these conditions.
Now of course nylon does have an initial tear strength advantage. I could be wrong, but everything I’m reading is that this is overstated and the difference is no more than 20% and that’s ignoring that nylon loses about 10-15% of its strength when wet, whereas poly does not. If we grant nylon a 20% tear strength head start, the polyester would still be 6x stronger at the end of this exposure.
Of course this might be a completely unrealistic amount of UV exposure that has no relevance to real world conditions. So is UV exposure a real problem with nylon tents? How much UV exposure a tent gets will vary widely, but I think there is good evidence that UV degradation is a real problem with nylon tents. In addition to my earlier quote showing Nemo saying that polyester is stronger over the normal lifespan of the tent, SlingFin writes “UV damage will still probably be the limiting factor in a [nylon] tent’s lifespan” while MoonLight Tents write “if you used both side by side for a couple of weeks the polyester would be significantly stronger than the nylon“. We also see Rainy Pass tent repair writing about nylon tents “the main issue that we see is UV damage or “sun rot.”
So I think it is clear that UV degradation is a major issue for nylon tents. I feel that much of the nylon vs poly debate has been overly generous to nylon as folks are quite to tout that nylon is stronger, without much regard for how (1) this difference is typically overstated and (2) nylon weakens substantially when wet and massively with UV exposure while poly does not. The ability of poly to maintain its strength over time and a wide range of conditions is a major advantage.