Are you using pressure-sensitive tape to bond something to plasticized material? Be prepared, because most pressure-sensitive adhesives don’t respond well to plasticizer. Plasticizer is a chemical compound that is often added to other plastic materials to create a softer and more flexible base material. The IUPAC (International Union of Pure and Applied Chemistry) defines a plasticizer as, “a substance or material incorporated in a material (usually a plastic or elastomer) to increase its flexibility, workability or distensibility.”
An example that we can all relate to is Polyvinyl Chloride (PVC). PVC is the third most widely produced synthetic plastic polymer in the world, after polyethylene and polypropylene. The solid plastic is most often used to make pipes, vinyl flooring and siding, hoses, cable coatings, medical devices and plumbing and automotive parts. It is also commonly found in upholstery, housewares, shower curtains, raincoats, toys, school supplies, food packaging and shoes. Plasticizer is added to the PVC formulation to increase its softness and flexibility.
Seasoned members of the pressure-sensitive tape industry have dealt with applications that require an adhesive to bond to a plasticized material. These applications can be very difficult to handle! Adhesive tapes often bond well to PVC and other plasticized materials initially, but they do not perform well over time.
As noted, plasticizer adds flexibility and softness to a plastic or rubber; however, that flexibility doesn’t last forever. You may have noticed that some flexible plastics and rubber get brittle and crack with age. The plasticizer migrating out of the material causes this loss of flexibility.
When a pressure sensitive-adhesive is applied to a plasticized material, the plasticizer in the material will migrate into the adhesive. Since plasticizer adds flexibility and softness, it does the same to the adhesive, changing the performance characteristics of the adhesive tape. The plasticizer often softens the adhesive to such an extent that the adhesive just turns to “goo” and loses all of its properties. This plasticizer migration and loss of adhesive performance is what makes bonding to plasticized materials so difficult.
There’s no stopping plasticizer from migrating into the adhesive, but acrylic adhesives can be modified so there is little or no noticeable change in the performance. Special monomers are co-polymerized to produce a cross-linked structure in the adhesive, which helps to reduce or slow down the plasticizer migration and help the adhesive maintain performance. If you have a tape application involving plasticized material, contact your adhesive tape supplier and ask for a plasticizer-tolerant adhesive.
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