Abstract
To investigate relationship between hot tack strength and entanglement behavior, two PSs (polystyrene) that having nearly equal molecular weight (Mw=2.0×105) but different molecular weight distribution (Mw/Mn=1.04 and 1.94) were used. Effects of molecular weight distribution on hot tack strength and rheological properties were discussed. Thin layered PS on PET (Poly (ethylene terephthalate)) film as the substrate was prepared using PS/THF (Tetrahydrofran) solution. Hot tack tests were performed under three different peeling rates at 140℃ with 1.0 to 100 sec of heat seal time for all tests. The surfaces after tests were observed by optical microscope. The number of newly generated entanglements on a polymer chain under several heat seal time was calculated by measuring dynamic shear viscoelasticity. As a result, we could determine critical generated newly entanglement number to show minimum hot tack strength. The critical value was about 0.02. PS having broad molecular weight distribution exhibited slightly lower critical value than that having narrow molecular weight distribution. In addition, the failure types were quantitatively classified based on the newly generated entanglement number.
