Autoclave Steam Setting for Twisted Yarns
topic
Yarn autoclave heat setting loads twisted yarn packages or hanks into pressure vessels and exposes them to saturated steam at 110 to 135 degrees Celsius for polyamide and 130 to 140 degrees Celsius for polyester for 20 to 60 minutes under saturated conditions that penetrate through the package depth, setting the twisted yarn configuration by thermal relaxation of the residual twist stress that causes snarling in unset yarn.
Role
Eliminates the twist liveliness of twisted synthetic yarns by thermally relaxing the internal stresses created during twisting through the combination of steam heat and moisture penetration that activates polymer chain mobility within the glass transition region, with autoclave setting being the standard method for sewing thread, hosiery, and knitting yarn where twist snarling in unset yarn would prevent reliable processing on knitting and sewing machines.