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Adhesives

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  • How can I control foam in my adhesive applications without getting craters?
    Jim Reader
    Adhesives –
    Specialty Additives

    Foam and craters are often two sides of the same coin, as craters are often created by the defoamers used to control the foam. Most defoamers contain insoluble and incompatible carrier fluids in order to break the foam lamellae, but these materials are also low surface energy materials that can cause localized de-wetting in the drying film. This is especially problematic on substrates like plastic, foils and silicone release liners.

    However, no two problems or formulations are the same, so Air Products offers a range of defoamers to help formulators find an optimum defoamer for their adhesive. This range includes conventional oil-based defoamers, such as Airase® 4500 defoamer, that provide strong defoaming performance, as well as novel molecular defoamers, like Surfynol MD-20 and Surfynol® AD01 defoamers, that can reduce microfoam and haze without causing surface defects.

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  • How can I eliminate haze in clear label laminating adhesives?
    Jim Reader
    Adhesives –
    Specialty Additives

    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.

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