Determination of Critical Tearing Energy of Polymer Films

Introduction Thin polymer fi lms are fi nding increasing interest in biological sciences and semiconductor packaging, along with their popular application as packaging materials. Researchers also show interest in studying mechanical stresses and fracture behavior in soft biological materials [1, 2]. In many of these applications, the fi lms need to experience severe mechanical stresses during handling as well as actual usage. While most of these polymer fi lms are durable under tensile stresses, they are very prone to failure upon tearing. Hence, it is quite important to know the critical energy release rate during fracture of these fi lms for accurate material design. A common technique to measure the critical fracture energy during fracture of rubber-like materials is trouser-tear test [3]. This method got its name because the specimen for these tests consists of a rectangular sheet cut along its long axis to form a trouser shaped sample (Figure 1). The ‘legs’ of the trouser specimen are then pulled in opposite directions to create tearing action. Determination of critical fracture energy from other test methods requires accurate determination of crack length, whereas the critical energy release and rate of crack propagation during a trouser-tear test are independent of crack length and sample geometry. Sandip Basu, Ph.D. Agilent Technologies