Universality in the velocity jump in the crack propagation observed for food-wrapping films for daily use

The velocity jump found in the crack propagation for rubbers has been a powerful tool for developing tough rubber materials. Although it is suggested by a theory that the jump could be observed widely for viscoelastic materials, reports on a clear jump are very limited and, even in such a case, reproducibility is low, except for elastomers. Here, we use a mundane food-wrapping film as a sample and observe the crack propagation velocity while pulling the sample at a constant speed in the direction perpendicular to the crack. As a result, we find that the jump occurs at a critical strain with high reproducibility. Remarkably, the plot of the crack-propagation velocity as a function of strain can be collapsed onto a master curve by an appropriate rescaling, where the master curve is found to be universal for changes in the pulling speed and in the sample height within the ranges that could be explored. The present study shows that the jump could be observed if the material exhibits a glass transition in rheology, even if more than one structural relaxation occurs as in many viscoelastic materials, although a single relaxation of the glass structure is assumed in the previous theory. This finding suggests the possibility that the velocity jump could be observed in any viscoelastic material that exhibits a glass transition. Our results provide constraints on future theories and open an avenue for the velocity jump to become a tool for developing a wide variety of tough polymer-based materials. • Velocity jump in crack propagation is observed in food-wrapping PVDC films. • The jump is found to be highly reproducible in a dynamic stretching experiment. • Crack velocity collapses onto a master curve as a function of absolute stretch. • The master curve is universal for changes in pulling speed and sample height. • Glass transition triggers the jump even in polymers with multiple relaxations.