In addition to stabilization of the raw materials, increased performance of an adhesive can also be achieved by the addition of antioxidants to the completed formulation. Typically the antioxidant is added during the compounding stages of an adhesive.
1. Stabilization of SIS Hot-Melt Adhesives
SIS-based HMAs degrade under high-temperature compounding and application conditions. Degradation of the bulk SIS HMA results in skin formation, viscosity changes, and discoloration. In a pressure-sensitive adhesive (PSA) film application, the film can degrade under moderate storage conditions, resulting in loss of tack and peel strength. Improved performance of both the bulk adhesive and the PSA film can be achieved with the addition of AO-2 (Figs. 18 and 19).
Figure 18 Stabilization of an SIS HMA: color development during oven aging at 150°C (300°F). |
Figure 19 Stabilization of an SIS HMA: peel adhesion after oven aging at 38°C (100°F). |
Figure 20 Stabilization of an EVA HMA: color development during oven aging at 170°C (338°F). (O) onset of skinning. |
Figure 21 Stabilization of an EVA HMA: melt viscosity during oven aging at 170°C (338°F). (O) onset of skinning |