Why is Borax used In Adhesives?

Manufacturer: We are using Polyvinyl acetate and Polyvinyl alcohol emulsion in combination with starch as bonding agents for paper and textile materials. In view of our concern over toxicity level of our compounding ingredients, we've removed borax from our formulations.

However we encountered a drop in the quality of our products in our lab evaluation due to delamination where the adhesives are being applied. Can you help us?

 John Woon (Senior Latex Consultant):  I'm not surprised at all by your findings.

Borax, also known as sodium borate or sodium tetraborate is often added to water-based adhesives especially those containing starch and Polyvinyl alcohol to enhance the tack and "body" (i.e. green strength) of the adhesive by crosslinking conjugated hydroxyl groups. Such cross-links are formed through the borate anion structure leading to a more highly branched polymer with higher molecular weight which accounts for the increased in viscosity, tack, and rheology properties of the resulted adhesives.

I don’t see why you should be unduly worried about the toxicity of borax because it is one of FDA's (USA) approved materials used in the manufacture of paper and paperboard products for food packaging as long as you don’t add borax directly into the food.

If you still insisted in removing borax from your formulation, you should have replaced it with other tackifiers and latex thickeners.

It might interest you to know that "Flubber Slime" that is popular among children is actually made by mixing Polyvinyl acetate or Polyvinyl alcohol emulsion with borax.