ボーイング現象の解析―テンタ―内における変形挙動の観察―
Analysis of Bowing Phenomenon-Observation of Deformation Behavior in Tenter-
野女村千里・山田 敏郎・松尾達樹
Nonomura, Chisato / Yamada, Toshiro / Matsuo, Tatsuo
The successive distortion patterns of the drawn line were observed over the whole tenter in order to analyze the "bowing phenomenon" which causes the unevenness of the properties in the transverse direction of film. From these observations, the following results were obtained for Poly(ethylene-terephthalate) (PET) film :
(1)A straight line drawn across the width of the film before a tenter does not change during the pre-heating zone and remains straight. In the beginning stages of the transverse stretching zone it changes to a convex curve (reverse bowing in to the travelling direction of film). The convex distortion becomes a maximum in the zone, and then towards the end of the zone it again becomes straight then changes to a concave curve at the end of the pre-heating zone. At the beginning of the thermo-setting zone the concave distortion becomes a maximum after with it scarcely changes and remains at maximum concave distortion (bowing distortion). This is usually observed as a "bowing phenomenon".
(2)Higher temperature in the thermo-setting zone leads to increased bowing distortion.
(3)The cooling temperature does not influence the bowing distortion.
(4)Relaxation or re-stretching in the transverse direction in the thermo-setting zone influences the bowing distortion, with greater relaxation leading to more bowing distortion or higher re-stretching creating less bowing distortion.
Key words: Bowing phenomenon / Transverse stretching / Tenter / Thermo-setting / Poly (ethylene-terephthalate) film