The crack propagation behavior of pre-cut slide-ring (SR) gels with movable cross-links is investigated and compared to that of fixed cross-link (FC) gels under uniaxial stretching at a constant speed. Two fracture stages with 20-fold difference in crack velocity are observed for both SR and FC gels. At the beginning, the crack propagates slowly, and the crack propagation resistance is in good accordance with the evaluation based on tearing modulus T_r, the initial slope of J-integral – crack tip opening displacement (CTOD) curve. Higher T_r and slower crack velocity are observed in SR gels compared to FC gels with similar modulus. Moreover, T_r decreases and crack velocity increases with increasing modulus (cross-linking density) for FC gels, whilst both parameters are modulus-independent for SR gels. This means that the slow mode crack propagation resistance of SR gels is dominated by the sliding movement of cross-links instead of the cross-linking density. However, as the strain energy input exceeds a critical value, crack accelerates abruptly and overtakes the sliding dynamics of the cross-links, thus the fracture behavior of SR gels resembles that of FC gels. Our results have revealed the strong correlation between the cross-link mobility and crack propagation resistance of SR gels.

研究了具有可移动交联的预切割滑环（SR）凝胶的裂纹扩展行为，并将其与固定交联（FC）凝胶在恒定速度单轴拉伸下的裂纹扩展行为进行了比较。对于SR和FC凝胶，观察到两个断裂阶段，裂纹速度相差20倍。起初，裂纹扩展缓慢，并且裂纹扩展阻力与基于撕裂模量T _r（J-积分-裂纹尖端开口位移（CTOD）曲线的初始斜率）的评估结果非常吻合。与具有相似模量的FC凝胶相比，在SR凝胶中观察到较高的T _r和较慢的破裂速度。而且，T _r对于FC凝胶，随着模量（交联密度）的增加，抗弯强度降低，裂纹速度增加，而对于SR凝胶，两个参数都不依赖于模量。这意味着SR凝胶的慢模裂纹扩展阻力主要是由交联的滑动运动而不是交联密度决定的。然而，当输入的应变能超过临界值时，裂纹突然加速并超过了交联的滑动动力学，因此SR凝胶的断裂行为类似于FC凝胶的断裂行为。我们的结果表明，SR凝胶的交联迁移率和抗裂纹扩展性之间具有很强的相关性。