I see a LOT of recycled wool tutorials. Almost all of them will say "you must use 100% wool". I say, that's great if you got it, but blends can work just as well in most cases, and there are a lot of fun patterns & colors out there in blends. A huge factor in your blend is whether or not the other fibers are synthetic or animal fiber. I consider anything animal fiber "wool" in my head when figuring out a blend. If something is 80%wool/20% angora, it is 100% "wool". If it is 80%wool/20% nylon, now that is something different. Generally, the more wool (or animal fiber), the better & easier they will felt (or full). I don't mind taking chances on blends for some projects though.
I am making **** (secret Christmas presents... more info on that coming soon to my blog), and didn't really need water repelling attributes (though they were repelling the water in the wash quite well), just felted wool. I threw in 3 blends that were lower in wool content than I will sell. All 3 felted up nicely and will be perfect for my projects! Here are pictures of the sweaters, and the seams I cut. I pulled at each of the cuts before taking the pics, so you can see there is no unraveling at all. The sweaters' fiber contents are:
dark fair isle - 60% wool, 40%acrylic (60% animal fiber)
pale aqua - 48% wool, 22% viscose, 16% nylon, 9% angora, 5% cashmere (62% animal fiber)
pink stripes - 50% wool, 20% rayon, 15% nylon, 10% angora, 5% cashmere (65% animal fiber)
I can't guarantee that all blends this low will felt, but the majority of the time, they will.
Now when you are using wool for diaper covers (longies, soakers, wool wraps), there are some different rules. I would not recommend anything under 80% animal fiber for diaper covers (though some lower blends will work fine, many will not). I have diaper covers that I have made from a 80% wool/20% nylon sweater, and they work fine, though of course, 100% wool is best when available. Never use blends with cotton, or silk, as they will wick moisture, and will retain smells.
Any questions class? ;)