Over the years I have only received a couple examples of shrinkage in items I made out of Dyneema Composite Fabric. One piece of feedback in which some .8oz DCF shrank considerably prompted me to check my test pieces I have in regular use and I found some in one piece, albeit to a much lesser extent. The feedback piece used .8oz DCF due to a custom request. I normally use .51oz DCF. The .8oz fabric showed much more shrinkage than what I found in .51oz and I only found shrinkage in one of the .51oz test pieces. None in others.
There is a theory out there that suggests heat is the catalyst for this shrinkage when the fabric is not under tension. I have more testing to do but as far as I can tell this seems to be true. The feedback example shrank in shipping and the test piece is a pullover that lives in a running pack that is often against a body and in the sun. I assume the feedback example saw some high temperatures while in transit, either in a vehicle or facility, and the test piece is subject to warm body temperatures and greenhouse effect inside a bag in the sun, day in and day out.
DCF from the factory has very little stretch in any direction. Both pieces I have handled that had shrinkage gained a stretch in the dimension that shrank. I assume this is due to the laminate mylar film shrinking and releasing tension from the Dyneema fibers. In both cases I was able to pull that stretch back out, very close to it’s original dimension without affecting it’s integrity. It took a few minutes to find the stretch and pull that direction back out, but the fabric remained fully waterproof and had the same feel. Again, I assume this is pulling the mylar film back out to the dimension of the Dyneema fibers so that when you place tension on the fabric, it is received by the strong fibers that do not stretch, rather than the film that does.
There are many different kinds of fabrics that use Dyneema. I don’t know that this technique applies to all of them (I would assume not), but for the specific Dyneema Composite Fabrics that I use, this appears to work well. In my test piece the shrinkage was slow and minimal enough that I didn’t notice the change. I noticed that it felt tight in certain dimensions, but since it slowly progressed to that point I didn’t remember it’s original fit and assumed I had built it small. For anyone who has a DCF item that feels tight, I would encourage them to check for this stretch. If any is found, pull that section out, but be careful not to put too much tension on seams. Try to pull the fabric sections from their edges, not through a sewn or taped seam, although DCF taped seams have pretty incredible sheer strength.