- June 01, 2003, David J. Bentley Jr., RBS Technologies
In the war against foam that often is waged when using aqueous coatings and adhesives, the first line of defense simply might be a dictionary. The battle to reduce or eliminate foam involves defoaming agents and antifoaming agents. A dictionary can offer information on how these two materials differ.
A defoamer is a product that attacks foam which forms in an aqueous product during mixing or use due to the introduction of air. This air forms bubbles that do not break. Accumulation of these bubbles then results in formation of foam. Large amounts of foam can be very troublesome and can cause problems with appearance of a subsequent dried material, maintenance of proper coating weight, slow running speed, etc.
Antifoam is a product that prevents foam from forming during the use of an aqueous product. When water-borne adhesives or coatings encounter a situation in which air might become entrapped in them, the antifoam they contain prevents the formation of bubbles.
Thus, the difference between the two materials is the point of incorporation of the additive into the aqueous product. Addition of antifoam occurs before use so foam does not form. Addition of defoamer occurs after foam has formed to reduce or eliminate it.
Should you use an antifoaming agent or a defoamer? Based on the above comments, the answer should be obvious. A manufacturer of an aqueous product will add antifoam to a material as a component of the formula if a suspicion exists that foam will form during a converting operation using the product. The manufacturer is trying to anticipate potential problems when purchasers use the aqueous product.
A converter planning to use a water-borne adhesive or coating might add antifoam for the same reason — an ingredient to prevent foam from occurring. A converter also could use a defoamer if foam formation was causing severe problems during processing. This means an aqueous product could contain antifoaming agent and defoamer.
Is the use of both antifoam agent and defoamer in a product during a converting operation good or bad? There is no simple, straightforward answer to this question.
Using both products is good in the sense the combination will undoubtedly go a long way toward making certain no foam will hinder the converting operation.
The disadvantage to the use of both types of materials is that both antifoam agents and defoamers sometimes can detract from the final properties of an aqueous adhesive or coating. Decreased bond values are one obvious disadvantage that can occur. Aqueous heat seal adhesives may not adhere as well during a sealing operation or develop sufficient bond strength. Aqueous PSAs may not exhibit the necessary peel strength.
Unfortunately, this brief treatment of antifoaming agents and defoamers cannot provide all the answers to their use. They are excellent materials that do their intended job. When foam is a problem, a converter should definitely use them. The secret is in the selection of the proper material and using the lowest level necessary to accomplish the task of foam elimination or reduction.
An excellent source of help is available from the technical service representatives of the manufacturers of the foam-fighting materials. They can provide small quantities of various materials for testing, or they can perform tests on aqueous products a converter sends to them.
Taking advantage of such services during initial evaluation of new water-borne materials will attack a potential foam problem in the bud and prevent the need for an extended war on foam during a commercial operation.
David J. Bentley Jr. is a recognized industry expert in polymers, laminations, and coatings with more than 30 years of experience in R&D and technical service. Contact him at firstname.lastname@example.org.