I tend to be rough on buttons (or maybe I’m just gaining weight). I started using Kevlar thread to sew fire toys and found it is very strong. I now use Kevlar thread for all my sewing. On buttons, I don’t need to use as much thread to secure them and the thread is tougher than the fabric I sew into. By weight, Kevlar is five times stronger than steel wire and is used in bulletproof vests. Do NOT try to break it by hand — you’ll just hurt yourself. The very thin thread works well with beads — it’s very abrasion resistant — and there are thicker varieties that I use for sewing leather.