What is a sil/pu fabric?

Usually it’s primarily silicone treated on one side and primarily PU coated on the other side.  There are different kinds/grades of PU used though, some higher quality and more durable than others.

PU side can be taped, and “usually” silicone side can be seam sealed with silicone adhesive, caulk, etc. I quote usually, because sometimes they also mix silicone and PU together for one side and decreases effectiveness of both taping and silicone seam sealing.

Even with high quality PU, it has a tendency to weaken the fabric some, whereas a double silicone coated fabric has it’s tensile, tear, strengths increased some.  Say you had the same exact base nylon fabric, but with one fabric it’s PU coated (one or both sides), and the other is double silicone coated–the latter will definitely be somewhat stronger and a little more long term durable (not necessarily the HH mind you, but the overall fabric itself).

The main advantage is the combo of being able to tape the fabric, and with higher quality PU coating, if the fabric is otherwise conducive to it, it seems that you can get both a higher AND more durable/long lasting HH for the fabric. But HH is also strongly affected by other variables such as thread count, fiber size and uniformity,  etc.

The old ripstops designs deceased the HH whatever the coating.

I know this thread is over a year and a half old but I thought I would correct something anyway because I have been trying to find out the same thing that Justin Baker is asking.  Justin W is confusing a sil/pu coating with a fabric which uses silicone on one side and polyurethane on the other.  Modern silpolys and silnylons have begun using a silicone and polyurethane mixture in an attempt to be a bit more environmentally friendly.  I believe this has something to do with the solvents needed for silicone so the idea is that mixing in polyurethane lessens the amount of silicone and therefore less solvent utilized/escaping into the environment.  Products like this one:

https://ripstopbytheroll.com/collections/waterproof-polyester-fabric/products/1-6-oz-silpoly

are sil/poly on both sides not sil on one side and poly the other.

I would put forward the question, if anyone else with more knowledge ends up here again, of how does this mixture coating compare to just silicone coating.  Is it as easy to repair by simply re-coating it manually?  Silicone coatings increase the strength, resilience, and UV resistance of the fabric – is any of this changed or lessened by mixing the sil with PU?  How does it affect the abrasion resistance of the silicone etc etc.

Cheers