Hollowness of the hollow polyester UDY increased after cool drawing,decreased after heat drawing, and was down a little while increasing drawing ratio.

• 冷拉伸后，涤纶未拉伸丝的中空度变大，热拉伸则相反；随着拉伸倍数的提高，涤纶未拉伸丝的中空度有所下降。