How can I eliminate haze in clear label laminating adhesives?
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Haze is often caused by the presence of tiny bubbles or microfoam that is trapped in the adhesive film. It can also be caused by the use of some oil defoamers when the difference in refractive index between the oil carrier and the adhesive binder causes the defoamer droplets to be visible as haze. Both problems can be solved by using molecular defoamers such as Surfynol® MD-20 defoamer or Surfynol AD01 defoamer.
Small (<20 micron-sized) bubbles rise too slowly to be released from an adhesive film; therefore, they cannot be effectively “defoamed,” and an alternative approach is needed. Deaerators that are molecular defoamers work by lowering the surface tension at the surface of the trapped bubble, allowing the trapped air in the bubble to dissolve into the liquid phase quickly, before it can become frozen in place as the adhesive film cures. The air then diffuses to the adhesive surface and is released, dissipating the microfoam and eliminating the haze. Molecular defoamers also do not contain oilbased carriers, so they do not create haze through differences in refractive index with the polymer.