Reducing drip and sag

in spray adhesives

A common problem encountered when applying an adhesive or coating to a vertical surface is dripping or sagging. This is especially true when the product is spray applied. It is difficult to formulate adhesives that are fluid enough to spray without clogging the nozzle, but viscous enough to cling to a vertical surface.

Formulators have taken several different approaches to solving this problem. Some of those approaches include: ignore it, give up one aspect of product and allow it to clog the nozzle or drip but not do both, use a thickener that thins to exit the nozzle but firmly adheres to the wall. This last scenario enhances the end user experience while also creating the perception of a higher quality product. The question is: which thixotropic thickener works best?

One worthwhile solution is the use of a cellulosic thickener. Cellulosics promote shear thinning through the nozzle avoiding clogging, but then rapidly thicken to spread evenly on the surface without dripping or running. Additionally, cellulosics promote excellent wet tack. Their use allows larger work areas to be treated, speeding installations.

When selecting a cellulosic thickener there are a few key aspects to consider:
-    Is my product solvent based or water based?
-    To what kind of surface is my product being applied?

Depending on the answers to the questions above, there are a few different choices for thickeners. One option is the use of METHOCEL™ methylcellulose. METHOCEL™ A grades form strong gels in water based formulations. There are other METHOCEL™ (E, F, J, and K) grades based on hydroxypropyl methylcellulose (HPMC) that will thicken both solvents and water. 

Another option is to use a related synthetic POLYOX™, poly(ethylene oxide) polymer. POLYOX™ based adhesives are used to adhere glass, steel, painted metal, paper, wood, and textiles. ¸

A third option is for solvent based adhesive formulations. ETHOCEL™ ethylcellulose, is solvent soluble, water resistant, and is particularly suited to thicken solvent based adhesives. 

Cellulosic thickeners are versatile, multi-functional products that support the needs of spray applied adhesives. Formulators no longer need to make the either/or choice, they can now make the and choice. Make a spray adhesive that does not clog the nozzle and adheres to the surface.

If you would like to learn more about these products or discuss other aspects of your adhesives formulation, our dedicated team wants to be a resource for you. Call us at 1.855.407.7176, email us at industrialcellulosics@chempoint.com, or go to our Contact Us page to reach us.


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