This article analyzes the mechanism of crease. It classifies the role of the rheological properties of fiber and the role of frictional force between textile elements in crease. Crease angle 0 can be related to the above-mentioned two factors by the following equation : O=OI-O2. O1 is the inherent crease angle of fiber and 02 is the fraction originating from the frictional force in the recovery process. Therefore, it should be possible to evaluate O1 from an elastic recovery test in which

more »

... undergo the same rheological history as in crease. In a fixed group of poplins constituted of various textile fibers, there is a good correlation between the crease angles of these fabrics heat-treated properly and an angle Oe =180 (1-P.S. 100 ~' Where PS. is the residual strain ratio at 2% strain in tensile stress relaxation recovery test. The time dependence of the crease angle is strongly influenced by the stress relaxation character of fibers. 02 can be depressed by suitable heattreatment or oiling. The depression of the 02 in the heat-treated fibers is presumably due to the reason that the pressure of contact, mainly between warp and weft, decreases by the thermal stress relaxation of fibers. 42