材料期刊网

文中以医用级高分子聚氨酯(TPU)为原材料,通过热压成型制备厚1.2 mm TPU片材,并制取75×4哑铃型拉伸试样.在电子万能试验机上以较高的恒定拉伸速率进行拉伸,预先设定应力到某一设定值后停止拉伸,然后应力以一定速度进行减载.实验探索了整个拉伸-回复循环中应力与应变的关系,研究了拉伸速度对医用级TPU拉伸强度及断裂伸长率的影响,并对拉伸过程中出现应力发白现象进行探究.结果表明,TPU是一种强而韧的硬弹性高分子材料,在高应力大形变下由弹性提供的可逆形变约80％,粘性提供的不可逆形变约20％.在高应力下材料内部孔洞尺寸变大,由此引起材料由透明转而发白,此光学现象可反复发生.

Medical grade thermoplastic polyurethane (TPU) was used as materials in this paper.Hot-pressing machine was used to prepare TPU sheet of which the thickness was 1.2 mm and was made into 75 × 4 dumbbell tensile samples.Tensile stress of medical grade TPU samples was measured by electronic universal testing machine during fast deformation and subsequent holding at a prefixed tensile stress,then normal stress decreased linearly with the elapsed time until it become to zero.The strain stress and stain ratio in the whole stretch-recovery cycle was explored,understand the relationship between tensile speed and the tensile strength,extension ratio;explored the phenomenon of stress whitening in tensile process.The results show that this medical grade TPU is a high strength,high extension ratio,hard elastic polymer material.The reversible elastic provides 80％ deformation and the irreversible viscous provides 20 ％ deformation under the high stress.The colour of TPU could turn from transparent into white under the high stress.This special optical phenomena is caused by the stress inducing hole become larger,and this phenomenon can happen over and over again in stretch-recovery processing.