Investigation of adhesion and failure mechanisms in tie-layer adhesive/EVOH systems

Plexar(R)* adhesive resins are used as tie-layer resins (TLR) in multilayer films to bond non-polar polyolefin water barriers to polar oxygen barriers such as ethylene vinyl alcohol (EVOH). The mechanisms of adhesion at the interface of the TLR and the EVOH interface were investigated on model systems using Fourier Transform Infrared (FTIR) spectroscopy. The results generated indicate that these TLRs react rapidly upon coextruding with EVOH to form a significant amount of covalent bonds. This fast reaction is followed by a similar but much slower reaction. Other types of bonds are also involved in the reaction, e.g. II-bonding and dipole-dipole interactions. TLRs having different rates of bond formation and adhesion mechanisms were examined. Additionally, the failure mechanisms of Plexar(R) TLRs were investigated and found to be of a mixed mode type, i.e., cohesive/adhesive failure.