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Understanding Rubber-Based Pressure Sensitive Adhesives in Tape Products

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Industry Knowledge,Tom Brown Inc News

History

In 1845, a surgeon named Dr. Horace Day made the first crude surgical tape by combining India rubber, pine gum, turpentine, litharge (a yellow lead oxide), and turpentine extract of cayenne pepper and applying that mixture to strips of fabric. It was the first “rubber-based” adhesive and Dr. Day used it in his practice as a surgical plaster. Larger scale manufacturing of similar medical tapes began in 1874 by Robert Wood Johnson and George Seaburg in East Orange, NJ. That company would soon become the Johnson & Johnson Company we know today. Later in 1921, Earle Dickson who bought cotton for Johnson & Johnson noticed that the surgical tape kept falling off his wife Josephine’s fingers after cutting them in the kitchen. He fixed a piece of gauze to some cloth backed tape and the first Band-Aid ® was invented. It took almost 75 years from Dr. Day’s first crude tape until the early 1920’s when the first industrial tape application appeared. The application was electrical tape (although the adhesive was more of a cohesive film than the electrical tape we know today) to prevent wires from shorting. The second major industrial tape application was a result of the rise of the American automobile in the 1920’s. Two-toned automobiles were becoming popular and automakers needed a way to produce clean, sharp paint lines while using the new automatic paint spray gun. They started using the surgical tape that was available but the paint wicked through the cloth backing and caused defective paint jobs. Richard Drew, an engineer at Minnesota Mining and Manufacturing (3M) happened to be at a local body shop testing their WetorDry® brand sandpaper in 1925 and he saw the workers struggling to get clean paint lines. He went back to his lab and created a 2-inch wide crimp backed paper tape that became the first “masking tape” for painting. Jumping ahead to 1942 and World War II, Johnson & Johnson developed duct tape to seal canisters and repair equipment for the military. The tape was a basically a polyethylene coated cloth tape with good “quick stick” properties that made it easy to use in the field for emergency repairs. The world never looked back and duct tape can be found in almost any home or toolbox.

What are Rubber Based Adhesives?

In simple terms, a rubber based pressure-sensitive consists of a natural or synthetic rubber to which various tackifying resins are added along with plasticizers, antioxidants, pigments, and UV stabilizers. These formulations can be delivered to the coating machine dissolved in organic solvents, dispersed in water, or in molten form as a hot melt. Some synthetic elastomers are also curable by radiation such as UV or electron beam(EB).

Natural Rubber Based Adhesives

The naturally occurring rubber harvested from rubber trees is the oldest type of adhesive base and is still in use today in various masking tapes and applications tapes used in the graphics industry. They are inexpensive, can be formulated with predictable adhesion properties, and work well in applications with low shear requirements.  These adhesives work well in ambient and low-temperature applications but will struggle when the temperature exceeds about 120°F.

Synthetic Elastomers

Adhesives and the resultant tapes made from this class of elastomers is very versatile and the most frequently used. These adhesives typically use styrene butadiene rubber (SBR) or styrene block copolymers such as styrene-butadiene styrene (SBS) , styrene –isoprene-styrene(SIS), or SEBS(styrene-ethyelene/butylene-styrene.. Block copolymers have thermoplastic styrene end blocks with an elastomeric midblock.  Different tackifying resins can be used for each distinct phase of the base and the resulting adhesives can be tailored to exhibit aggressive tack, high peel, and excellent cohesive strength. There are a variety of tape products made from these systems including double coated film tapes, transfer adhesives, foam tapes, and carton sealing tapes. These tapes can be used for interior bonding and assembly applications, fabricating foam gaskets and seals, and of course duct tape.

rubber based adhesives schematic microstructure

Strengths and Weaknesses

In general, rubber based adhesives are not UV or oxidation resistant which is why they tend to be used predominantly in interior applications. Having said that, antioxidants and UV stabilizer packages can be added to the formulation to help mitigate these weaknesses. Some synthetic elastomers exhibit vastly improved UV stability over natural rubbers. Chemical resistance can also be problematic as is resistance to elevated service temperatures (typically 180- 200°F at the top end). The great strength of rubber-based adhesives is their wide formulation latitude.  These adhesives can be compounded to be removable, repositionable, or extremely permanent. High strength foam bonding tapes can be made from rubber based adhesives or easily removable masking products can also be offered. Rubber based adhesive adhere to many surfaces including low surface energy plastics such as polypropylene and polyethylene. And to top it all off, rubber based adhesives are economical. They get the job done at a very fair price! Adhesive tapes made from rubber based adhesives have come a long way since Dr. Day’s first surgical tape and they still offer a cost-effective way to bond, seal, and protect. Contact Tom Brown, Inc. today for samples or more information.
Rick Alexander

About the Author

Rick Alexander is the National Sales Manager for Tom Brown, Inc. His early experience was in R&D, product management, and sales management for both Main Tape and Adhesives Research, Inc. Rick brings over 40 years of pressure-sensitive tape experience and Tom Brown’s world class converting capabilities to help solve customer bonding, assembly, and sealing challenges.

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