Wedge indentation characteristics of pressure-sensitive adhesives sandwiched by polyethylene terephthalate films

A wedge cutting method with a center-beveled blade is widely used for cutting various laminated sheets such as printed labels, optical adhesive sheets, and multi-functional adhesive films for electronic equipment. In general, the laminated sheet has a pressure-sensitive adhesive (PSA) in the intermediate layer. When a wedge blade indents to a laminated sheet, trouble occasionally occurs because of the blade getting with PSA and PSA flowing out from the cut surfaces. This problem has not been sufficiently clarified. Several reports exist about the cutting behavior of a laminated structure composed of paperboard and monolayer viscoelastic material; however, almost no reports exist on the cutting behavior of laminated sheets with PSA. Therefore, this paper aims to elucidate the effect of a wedge shape on the cutting behavior of a laminated sheet with PSA and polyethylene terephthalate (PET). The cutting characteristics of a 0.1 mm PSA layer sandwiched by upper and lower PET films of 0.1 mm were experimentally and numerically investigated. The cutting load response was measured using indentation depth when the apex angle of the wedge blade was changed. A CCD camera was also installed for investigating the side-view deformation of the laminated sheet. When an apex angle from 16° to 60° was chosen, the cutting force and the bent-up angle of the laminated sheet linearly increased with respect to the apex angle for certain shallow indentation depths. The experimental results showed that the cutting load response and deformed state of the laminated sheet were similar to those of the visco-elastic model based on finite element method (FEM) simulation. In addition, the peak force and the bent-up angle considerably increased with the apex angle, especially when a large apex angle was chosen The fact that the apex angle influenced the cutting characteristics of the laminated sheet during wedge indentation was clarified.