We have put on dozens of these patches to hats without threads melting. How are you adhering them? Did you use a protective sheet over the patch (teflon or other)? You cannot put an iron directly on these or it will melt. How high was your temperature set? We don't sell faulty products that we haven't used in this purpose ourselves. We'd be happy to send you a replacement to try with instructions on adhering without melting. Please message us if you'd like us to.